Case 1:CLINICAL VIGNETTES AND QUESTIONS - HEMATOLOGYA 57-year-old female complains of fatigue, tingling and numbness of her fingers and toes. The symptoms have become progressively worse over the last 6 months. She reports that she had changed her dietary habit to strict vegetarian diet two years ago. Physical examination shows pallor, jaundice and decrease in position and vibration sense in her toes. A complete blood count (CBC) shows: White blood cells: 4000/mm3 (normal: 5000 to 11,000/mm3)Hemoglobin concentration: 9 g/dL (normal:12-16g/dL) Hematocrit (Hct): 27 percent (normal: 36-46%) Mean corpuscular volume (MCV): 110 femtoliter (normal: 79-97 fL) Platelet count: 160,000/mm3 (normal: 150,000 to 450,000/mm3) She is diagnosed as having megaloblastic anemia and advised supplementation of vitamin B12.Questions:

1. Describe the risk factors, etiology, pathogenic mechanism, altered morphology & physiology, signs and symptoms, basis for signs and symptoms, differential diagnosis, screening and confirmatory investigations, prognosis and complications of macrocytic anemias.

Macrocytic anemia’s are subdivided into megaloblastic (eg. Folate or vitamin B12 deficiency) and nonmegaloblastic anemia.

Vitamin B12 Deficiency Folate deficiencyEtiology (risk factors):

Malnutrition, pure vegan diet, malabsorption (eg. Crohn’s disease, pernicious anemia), increased utilization (pregnancy), Diphyllobathrium latum (fish tapeworm)

Decreased intake (chronic alcoholics), malabsorption (Celiac disease), impaired metabolism (eg. Drug induced – methotrexate, trimethoprim), increased utilization (eg, pregnancy, hemolytic anemia)

Pathogenic mechanism of macrocytic anemia in folate and vitamin B12 deficiency

Vitamin B-12 and folate coenzymes are required for thymidylate and purine synthesis; thus, their deficiency results in retarded DNA synthesis. Impaired DNA synthesis causes delayed nuclear maturation and results in a block in cell division leading to large, nucleated hematopoietic cells. The cellular RNA and protein synthesis continue unabated and the cytoplasmic volume continues to expand. The enlarged calls are called megaloblasts. It affects all rapidly dividing cells: RBCs, leukocytes, platelets, and intestinal epithelium. As a result there is ineffective erythropoiesis. Megaloblastic precursors outside the bone marrow sinusoids are phagocytosed by macrophages and magaloblastic precursors undergo apoptosis causing pancytopenia (anemia, neutropenia, and thrombocytopenia)

Altered morphology & physiology

Vitamin B12 is in meat, eggs, and dairy products. Parietal cells synthesize intrinsic factor and hydrochloric acid. The gastric acid then converts pepsinogen to pepsin, and pepsin frees vitamin B12 from ingested proteins. Free vitamin B12 is bound to R-binders synthesized in the salivary glands. Pancreatic enzymes in the duodenum cleave off the R-binders

Folate is present in green vegetables and animal proteins in the form of polyglutamates. It is converted to monoglutamates by intestinal conjugase (inhibited by phenytoin). Monoglutamates are reabsorbed in the jejunum and converted to methyltetrahydrofolate, the circulating form of folate. Reabsorption is blocked by alcohol and oral contraceptives. Only a 3-4 month

and vitamin B12 binds to IF to form a complex. The vitamin B12-IF complex is reabsorbed in the terminal ileum. Vitamin B12 binds to transcobalamin II and is secreted into plasma, where it is delivered to metabolically active cells or stored in the liver(6-9 years).

supply of folate in the liver.

Signs and Symptoms

Symptoms usually do not arise until anemia is severe: pallor, dyspnea, palpitations, angina. Symptoms related to underlying disease. Smooth sore tongue with atrophy of papillae (glossitis), Neurologic disease: peripheral neuropathy, dementia, and subacute combined degeneration of the spinal cord (affects posterior columns, lateral corticospinal tract, dorsal spinocerebellar tract) due to involvement of B12 in fatty acid pathways

Similar to Vitamin B12 deficiency with the exception of neurologic disease.Increased risk of open neural tube defects in the fetus.

Differential diagnosis

Microcytic anemia (eg. Iron deficiency, thalessemia), Normocytic anemia (eg. Aplastic anemia, chronic renal failure)

Screening and confirmatory investigations (MCV > 100 um3)

Lab findings: decrease serum Vitamin B12, increased serum homocysteine and methylmalonic acid (most sensitive test for Vitamin B12 deficiencyPeripheral blood findings: pancytopnenia, oval macrocytes, hypersegmented neutrophils (five or more lobes) which is the maker for folate and vitamin B12 deficiencyBone Marrow Findings: megaloblastic nucleated cells with primitive open (lacy) chromatin pattern

Lab findings: decreased serum folate and RBC folate (best screening test), increased homocysteine, and normal mehtylmalonic acidPeripheral blood and bone marrow findings are similar to Vitamin B12 deficiency

Prognosis Treatment: IM injection of vitamin B12Takes about six weeks for hematologic abnormalities to be corrected but neurologic symptoms may take much longer.

Treatment: oral administration of monoglutamic folic acidPrognosis is good, tissues replenished even in malabsorption situations.

Complications Important to distinguish folate from vitamin B12 deficiency. Pharmacologic doses of folate will correct the hematologic findings of both folate and vitamin B12 deficiency; however, neurologic disease is not corrected and

may even worsen symptoms

Schilling test: used to localize some of the causes of B12 deficiency though not routinely performed anymore. Achieved by combining orally administered radioactive vitamin B12 with IF, or with pancreatic extract, or alone after pretreatment with antibiotics followed by a 24 hr urine collection to measure radioactive vitamin B12. Low levels are seen in defective GI absorption. If low, repeat with oral intrinsic factor with B12 to assess change, this will increase urinary excretion of oral dose if problem is due to lack of IF production. If this is low give oral antibiotic with B12 to assess change, this will increase urinary excretion if problem is parasitic. And if antibiotics do not help, the problem is likely one of absorption in the small bowel.Nonmegaloblastic macrocytosisOccurs in various clinical states, but all of which is fully understood. It is suspected in patients with macrocytic anemias in whom testing excludes vitamin B12 and folate deficiencies. There is incorporation of excess cholesterol and phospholipid into membrane, transferred form plasma lipoproteins. The RBC then attempts to maintain most energy efficient shape: target cells, spur cells.Differences from megaloblastic macrocytic anemia’s: macrocytes are round rather than oval, hypersegmented neutrophils are not presents, leukocytes and platelets are quantitatively normal, absence of glossitis and neuropathy, anemia may not be present, alcohol excess is the most common cause.

1. Liver disease2. Alcoholism: macrocytosis and bone marrow suppression can occur in the absence of

folate/B12 deficiency3. Reticulocytosis: reticulocytes are bigger than mature RBCs increased MCV4. Metabolic disorder: congenital deficiencies of purine or pyrimidine synthesis5. Drugs: hydroxyurea, AZT

2. Describe the normal anatomy and histology of the bone marrow.

Anatomy:Bone marrow is found in the medullary canals of long bones and in the cavities of cancellous bones (vertebral bodies, ribs, found inside the epiphysis or head of long bones). Cancellous bone has large, open spaces (marrow spaces), surrounded by anastomosing plates of bone.

Two types of bone marrow have been described based on their appearance on gross examination: red (hematogenous) bone marrow (color is produced by blood and blood forming cells) and yellow bone marrow (color is produced by great number of adipose cells). In newborns, all bone marrow is red and is active in production of blood cells. As the child grows, most of the bone marrow gradually changes into yellow marrow. In adults, red marrow remains mainly in the short and flat bones. Under certain conditions (severe bleeding, or hypoxia) yellow bone marrow is replaced by red bone marrow. Normal bone marrow biopsy will show 30-50% cellular components and approx 50% fat.

Histo:Bone:On a transverse section of a decalcified rib, we will find:-haversian canals (house blood vessels that connect osteocytes)

-Volkmann’s canals (connect haversian canals)-osteocytes in their lacunae-endosteum (part of the bone that does not participate in the ossification process and remains a soft tissue component). Bone marrow:-stroma: 3-D meshwork of reticular fibers containing hematopoietic cells and macrophages, made of collagen Type I and III, fibronectin, laminin, and proteoglycans-adventitial reticular cells (cells responsible for storing fat in the marrow)-sinusoids (discontinuous layer of endothelial cells)-blood vessels-Pluripotent hematopoietic stem cell -numerous cells undergoing hematopoiesis-Megakaryocytes

3. Explain the normal development of the formed elements of blood from bone marrow stem cells (hematopoiesis).

http://upload.wikimedia.org/wikipedia/commons/6/69/Hematopoiesis_%28human%29_diagram.png

GRANULOCYTE MATURATION

Overall trend is from larger to smaller size; round, fine nucleus to dark, segmented nucleus; increasing cytoplasm; no granules to primary (azurophilic) granules to specific (secondary) granules.

1. Promyelocyte (10-20 µm): round nucleus, reddish-blue and fine to slightly condensed chromatin, 1-2 nucleoli, increased basophilic cytoplasm, and primary (azurophilic) granules.

2. Myelocyte (10-18 µm): oval (to round) slightly indented nucleus; reddish-blue and slightly granular chromatin; nucleoli may or may not be present; moderate bluish pink cytoplasm; primary and specific granules (fine and pale). This is the first appearance of specific granules (neutrophilic, eosinophilic and basophilic). The eosinophilic myelocyte is the most easily determined with its coarse eosinophilic granules.

3. Metamyelocyte [ neutrophilic and eosinophilic ] (10-18 µm): indented nucleus (kidney bean); light blue-purple and granular chromatin; no nucleoli are present; moderate clear pink cytoplasm; specific granules are obvious.

4. Band Neutrophi l (10-16 µm): elongated, horseshoe nucleus; blue-purple and clumped granular chromatin; no nucleoli are present; abundant pink cytoplasm; specific granules. This cell stage is not distinguished for the eosinophil and basophil maturation.

5. Granulocytes: Mature granulocytes are divided into Basophils- bilobate nucleus, densely basophilic granules, found in blood Eosinophils- bilobate nucleus, eosinophilic granules of uniform size Neutrophils- multilobed nucleus, large spherical azurophilic granules

ERYTHROCYTE MATURATION

The overall trend in RBC maturation is large, pale nucleus to darker, smaller nucleus to loss of nucleus; increase in cytoplasm; gradual decrease in size; cytoplasm from intensely blue (full of RNA) to grayish (mixture of RNA and hemoglobin) to reddish (full of hemoglobin, no RNA).

1. Proerythroblast (14-19 µm): Nucleus is large with fine chromatin and nucleoli; cytoplasm is scant and basophilic.

2. Basophilic erythroblast (12-17 µm): Slightly smaller nucleus with slight chromatin condensation; increased cytoplasm and intensely blue (RNA abundance); no granules and no nucleoli present.

3. Polychromatophilic erythroblast (12-15 µm): Moderately condensed chromatin; lighter, grayish cytoplasm. The nucleus is condensed and intensely basophilic with coarse heterochromatin granules giving a characteristic checkerboard appearance.

4. Orthochromatophilic erythroblast (8-12 µm): Dark, opaque nucleus; gray-red cytoplasm (trace blue). The nucleus has become pyknotic and there is abundant acidophilic hemoglobin.

5. Reticulocyte (7-10 µm) Nucleus has been extruded; cytoplasm is reddish-pale blue. RNA is still present.

6. Erythrocyte (7-8 µm): No nucleus; orange-red cytoplasm; RNA is lost.

OTHER CELLS

1. Megakaryocytes (50-150 µm): Stages of maturation go from Megakaryoblast to Megakaryocyte to Platelets (small cytoplasmic fragments).

2. Monocytes (9 - 12 µm): Stages of maturation go from monoblast to promonocyte to monocyte to macrophage (in tissues). The nucleus is oval, horseshoe or kidney shaped and is usually eccentric. The chromatin is less dense than in lymphocytes. The cytoplasm is basophilic.

3. Lymphocytes (6 - 8 µm): Stages of maturation go from lymphoblast to prolymphocyte to lymphocyte. Small amount of pale cytoplasm.

T lymphocytes- mature in thymus B lymphocytes- mature in bone marrow

-Plasma cells- offcenter nucleus, clock-face chromatin distribution, ubundant RER and well developed Golgi apparatus

4. Describe the mechanism of folate trap in producing vitamin B12 deficiency.

Methylene-THF is formed from THF by the addition of methylene groups from one of three carbon donors: formaldehyde, serine, or glycine. Methyl tetrahydrofolate can be made from methylene-THF by reduction of the methylene group with NADPH. It is important to note that Vitamin B12 is the only acceptor of methyl-THF. There is also only one acceptor for methyl-B12, which is homocysteine in a reaction catalyzed by homocysteine methyltransferase. This is important because a defect in homocysteine methyltransferase or a deficiency of B12 can lead to a methyl-trap of THF and a subsequent deficiency. Thus, a deficiency in B12 can generate a large pool of methyl-THF that is unable to undergo reactions and will mimic folate deficiency.

5. Identify the biochemical reaction and enzyme that requires both folic acid and vitamin B12.

Methylcobalamin serves as an intermediate in the transfer of a methyl group from N5-methyltetrahydrofolate to homocysteine, forming methionine. In the process, N5-methyltetrahydrofolate is converted to tetrahydrofolate, the precursor of folate cofactors. This explains is how vitamin B12 (cobalamin) and folic acid metabolism are linked and explains why megaloblastic anemia of vitamin B12 deficiency can be partially corrected by ingestion of relatively large amounts of folate.

NOTE: disruption of the methionine synthesis pathway is the cause of neurological problems and that folic acid in the setting of vitamin B12 deficiency will NOT correct neurological manifestations.

6. Explain why methylmalonate levels are elevated in a patient with Vitamin B12 deficiency.

B12Methylmalonyl-CoA Succinyl-CoA (associated with myelin)

Vitamin B12 is required for the isomerization of methylmalonyl-CoA to succinyl-CoA by the enzyme methylmalonyl-CoA mutase. In vitamin B12 deficiency this reaction cannot take place and methylmalonyl-CoA and methylmalonic acid accumulate.

B12 acts as a cofactor for homocysteine methyltransferase and methylmalonyl-CoA

Case 2:A 58-year-old male who complains of mild fatigue for the past nine months is being evaluated. Physical examination reveals mild pallor and an enlarged spleen. Complete blood count reveals:White cell count: 68,000/mm3 (normal: 5000 to 11,000/mm3) Differential white cell count: 1% blasts, 3% promyelocytes, 10% myelocytes, 10% metamyelocytes, 15% bands, 50% segmented neutrophils, 3% monocytes, 3% basophils, 3%, eosinophils, 2% lymphocytes. Peripheral smear shows a few nucleated RBCs. Platelet count: 400,000/mm3 (normal: 150,000 to 450,000/mm3) Hemoglobin concentration: 9.4 g/dL (normal:12-16g/dL) Blood smear picture is shown below.

Questions:1. Describe the risk factors, etiology, pathogenic mechanism, altered morphology & physiology, signs and symptoms, basis for signs and symptoms, differential diagnosis, screening and confirmatory investigations, prognosis and complications of chronic leukaemias (both chronic myelogenous leukemia & chronic lymphocytic leukemia.

Chronic Myelogenous Leukemia Chronic Lymphocytic LeukemiaRisk factors Exposure to ionizing radiation and

benzeneEtiology t9;22 (95%)

-translocation of ABL proto-oncogene: ABL fuses with break cluster region (BCR) on chr.22chr.22 w/translocation is called Philadelphia chromosome

Pathogenesis Neoplastic clonal expansion of the pluripotential stem cell myeloid stem cell proliferation

-neoplasm of virgin B cellscan’t differentiate into plasma cells hypogammaglobulinemia (50%)

Altered morphology and physiology

Peripheral blood smear: ↑ leukocyte count (mainly neutros, metamyelocytes, basophils), ↑ platelets, ↓RBCs

Peripheral blood smear: ↑ # of lymphos w/dense nuclear chromatin and little cytoplasm; lymphos are very fragile and produce “smudge

Bone marrow: hypercellular due to hyperplasia of granulocytic and megakaryocytic precursors

Spleen: red pulp enlarged—looks like BM b/c of hematopoiesis

cells”

Bone marrow: complete replaced by neoplastic B cells

Involved LN: sheets of small round lymphocytes

Signs and sx (and basis)

-30-60y-initial sx are slow and nonspecific: fatigue, weakness, weight loss-Splenomegaly (extrameduallary hematopoiesis)dragging sensation-generalized painless lymphadenopathy (metastasis)

- >60y-often asx-generalized, non-tender lymphadenopathy-warm antibody autoimmune hemolytic anemia (IgG)

-neutropenia, noromocytic anemia (50%), thrombocytopenia (40%)

Differential diagnoses

Other chronic myeloproliferative diseases: polycythemia vera, essential thrombocytosis, myelofibrosis

Other B-cell neoplasms: Hairy cell leukemia (mature B cell tumor in elderly), Mantle cell lymphoma (also expresses CD5)

Screening and confirmatory investigations

-presence of Philadelphia chr (in the other chronic myeloprolif diseases we see JAK2 mutation)-low leukocyte alkaline phosphatase (do not see a leukemoid reaction as in other chronic myeloprolif diseases—↑WBC count with left shift and ↑ leukocyte alkaline phsphatase)

-mature B cells w/CD19, CD20, CD23, B cell receptor, CD5

-BM aspirate, peripheral blood smear

Prognosis/Complications

-enlarged spleen compromises local blood supplysplenic infarct

-blast crisis: accelerate and transform into AML or ALL in ~5 yrs (↑ in myeloblasts or lymphoblasts—more immature cells)

-course and prognosis is variable; ~survival=4-6yr-death due to infection b/c no Ig-as time passes, CLL transforms into aggressive tumor (resemble pro-lymphocytic leukemia or diffuse large B-cell lymphoma)then survival is <1yr

LAP: mature neutros have alkaline phosphatase in them—will take up the stain (neoplastic cells don’t—won’t take up the stain)

2. Identify the source and function of erythropoietin.

Source: Peritubular capillary endothelial cells of the kidney and to a much lesser extent liver.

Function: Acts on stem cells of the bone marrow to stimulate red blood cell production. Also, initiates the production of hemoglobin.

3. Identify the morphology and functions of the formed elements of blood (red blood cells, white

blood cells and platelets).

Formed Elements Morphology FunctionRBC Anucleate, biconcave Transports O2 & CO2 b/w

peripheral tissues and lungsPlatelets Small cytoplasmic fragments

derived from megakaryocytesPromotes blood clotting and prevents leakage of RBCs from damaged vessels.

WBC: Defense against infectionsNeutrophil Multi-lobed nucleus with

neutrally staining granulesPhagocytic. Important in acute inflammatory response.

Eosinophil Bilobate nucleus with large eosinophilic (red) granules of uniform size

Important in parasitic and protozoan infections. Involved asthma and allergic responses.

Basophil Bilobate nucleus with densely basophilic (dark blue) granules

Plays a role in parasitic and allergic responses.

Lymphocyte Round, densely staining nucleus. Small amount of pale cytoplasm

B cell = AntibodiesT cell = Cellular immune response, regulate B cells and macrophages

Monocyte Large. Kidney-shaped nucleus. “Frosted-glass” cytoplasm

Differentiates into macrophages, which phagocytose bacteria and damage cells. Also an APC.

4. Describe hemoglobin synthesis and degradation. Describe the factors that shift the oxyhemoglobin dissociation curve.

Heme synthesis:The enzymatic process that produces heme is called porphyrin synthesis.The pathway is initiated by the synthesis of D-Aminolevulinic acid (dALA or δALA) from the amino acid glycine and succinyl-CoA from the citric acid cycle. The rate-limiting enzyme responsible for this reaction, ALA synthase, regulated by intracellular iron levels and heme concentration. A low-iron level, e.g., in iron deficiency, leads to decreased porphyrin synthesis, which prevents accumulation of the toxic intermediates. The organs mainly involved in heme synthesis are the liver and the bone marrow.

Heme degradation:Degradation by macrophages in the spleen, after 120 days.heme is converted to biliverdin by the enzyme heme oxygenase (HOXG). NADPH is used as the reducing agent, molecular oxygen enters the reaction, carbon monoxide CO is produced and the iron is released from the molecule as the ferric ion (Fe3+). HMOX1/2 heme --------------> biliverdin + Fe3+ / \ H+ + NADPH NADP+

O2 COIn the second reaction, biliverdin is converted to bilirubin by biliverdin reductase (BVR):

BVR biliverdin -----------> bilirubin / \ H+ + NADPH NADP+Bilirubin is transported into the liver bound to serum albumin, where it is conjugated with glucuronic acid to become more water soluble. The reaction is catalyzed by the enzyme UDP-glucuronide transferase (UDPGUTF).

UDPGUTF bilirubin + 2 UDP-glucuronate ------------> bilirubin diglucuronide \ 2 UMP + 2 Pi bilirubin is excreted from the liver in bile. The intestinal bacteria deconjugate bilirubin diglucuronide and convert bilirubin to urobilinogens. Some urobilinogen is absorbed by intestinal cells and transported into the kidneys and excreted with urine. The remainder travels down the digestive tract and is excreted as stercobilinogen, which is responsible for the color of feces.References:Biochem BRS page 284Goljan page 199 and 359

Factors Affecting Oxygen-hemoglobin dissociation curveReference : first aid

Left shift Right shift↑in O2 affinity↓ metabolic needs↓pCo2↓T, ↓ H+, ↓ 2,3 DPGFetal Hb (increased in beta thalasemia, Goljan page 198)CO (Carbon monoxide)Bohr effect

↓in O2 affinity ↑metabolic needs↑pCo2↑T, ↑H+, ↑2,3 DPGRespiratory acidosisHigh AltitudeExersieSickel cell Methaemoglobin ( ferrous (Fe2+), which is normally is converted to the ferric (Fe3+) )

"CADET, face Right!" for CO2, Acid, 2,3-DPG, Exercise and Temperature

5. Compare and contrast the structure of HbA, HbA2, HbF, HbS.

HBA-2α/2β globin chains (97% in adults)HBA2-2α/2δ globin chain (2% in adults)HBF-2α/2γ globin chains (1% in adults)HBS-α2βS

2 globin chains (HBS is a predominant hemoglobin in people with sickle cell anemia. The alpha chain is normal. The disease-producing mutation exists in the beta chain, giving the molecule the structure, a2bS

2 (mutation in both beta chains!). People who have one sickle mutant gene and one normal beta gene have sickle cell trait which is benign.

Case 3:An 18-month-old boy presents with a painful left knee. His father reports that the child had large bruises following immunizations at 12 months. He also states that his wife’s uncle had a similar history of “easy bruising”. Physical examination reveals warm, tender, and swollen left knee. Remainder of physical examination is normal.Laboratory tests show: Platelet count: 330,000/mm3 (normal: 150,000 to 450,000/mm3), Activated partial thromboplastin time (aPTT): 80 seconds (normal: 27-32 sec) Prothrombin time (PT): 12 seconds (normal: 11-15 sec). The child’s plasma factor VIII activity is found to be 32% of a normal pooled- plasma standard, which is designated as having 100% activity or the equivalent of factor VIII.Questions:

1. Describe the risk factors, etiology, pathogenic mechanism, altered morphology & physiology, signs and symptoms, basis for signs and symptoms, differential diagnosis, screening and confirmatory investigations including genetics, prognosis and complications of hemophilia A and B.

Disease Hemophilia AHemophilia B

Etiology A: hereditary (X-linked recessive) 30% new mutationsB: hereditary (X-linked disorder)

Pathogenesis A: deficiency of factor VIII increased PTT (Intrinsic pathway)B: deficiency of factor IX increased PTT (intrinsic pathway)

Signs and Symptoms

Easy bruising, massive hemorrhage after trauma or operative proceduresRecurrent bleeds into the joints (hemarthroses)Petechia is characteristically ABSENT

Investigation Normal PT time; Prolonged PTT

Treatment Infusion of recombinant factor VIII; infusion of recombinant factor IX

Complication 15% of most severely affected patients, replacement therapy is complicated by the development of neutralizing antibodies against factor VIII

2. Describe the mechanism of coagulation of blood by both intrinsic and extrinsic pathways.

The coagulation pathways consists of 3 portions, the extrinsic, the intrinsic which finally converge into a common pathway.The extrinsic pathway is activated by factors extrinsic from the vessels in the blood, therefore when tissue is damaged, coagulation factors from these tissues activate the extrinsic pathway. The extrinsic pathway is mediated by Factor VII.The intrinsic pathways is activated by damage to the blood itself or the exposure of blood to collagen which are in the vessel walls. The intrinsic pathway is mediated by Factors XII, XI, IX and VII.The converged common pathway involves X, V, II and I. Of which Factor II (thrombin) is the most important due to the activation of many other pathways.

Remember PT tests for extrinsic and PTT tests for intrinsic.

Diagram:

3. Explain how the following laboratory tests help in distinguishing the common causes for bleeding: activated partial thromboplastine time, clotting time, bleeding time, Prothrombin time and platelet count.

Clotting time is the time required for a sample of blood to clot in vitro under standard conditions.

Bleeding time is the time it takes for a standardized skin puncture to stop bleeding.

Platelet count is part of the CBC and can give information about disorders involving low or high platelet levels. Normal platelet levels in adults are 150,000 – 400,000 / mm3

Activated partial throboplastin time (aPPT) measures the intrinsic and common coagulation pathway and is prolonged when there are reduced levels of factors XII, XI, VIII, IX, X, V, II and I activity. With a prolonged aPTT, these factors can be present in lower concentrations or present in normal concentrations being actively inhibited by other molecules. The aPTT is also sensitive to the presence of heparin bound to antithrombin and used to monitor the effects of unfractionated heparin.

Prothrombin time (PT) measures the extrinsic and common coagulation cascade and is prolonged when there are reduced levels of factors VII, X, V, II and I activity. PT is used to monitor warfarin. Because all vitamin K-dependent factors (II, VII, IX, X, protein C and protein S) are lowered by warfarin, eventually the aPTT will be prolonged too, but since factor VII has the shortest half-like the PT is prolonged initially.

Disorder Platelet count

Bleeding time

PT aPTT

Thrombocytopenia - -Hemophilia A or B - - - Von Willebrand’s disease - - - or DIC Vitamin K deficiency - - Bernard-Soulier disease - -Glanzmann’s thrombasthenia

- - -

4. Determine the assessment of risk of carrier state in a family with sickle cell disease. Solve problems related to recurrence risk in a family with history of sickle cell anemia (autosomal recessive).

Just use pedigrees and punnett squares on all possible combinations. Because the disease is inherited in an autosomal recessive fashion, an individual needs two alleles for the disease to be present and one allele for the carrier state.

Examples: Both parents have sickle disease - ss crossed with ss = 100% chance of sickle cell disease.One parent sickle cell disease, one carrier  - ss crossed with Ss = 50% disease 50% carrierand so on -   ss x SS = 100% carriersSs x Ss = 25% disease 25% unaffected 50% carriers

Ss x SS = 50% unaffected 50% carriersSS x SS = 100% unaffected

5. Based on pedigree analysis, differentiate between X-linked, autosomal recessive and autosomal dominant disorders.

Autosomal dominant

Autosomal Recessive

X-linked

6. Describe the role of vitamin K in blood clotting.

Vitamin K is an extremely important aspect of the clotting of blood. Clotting factors II, VII, IX and X are vitamin K dependent, which means that they need vitamin K as a cofactor for the gamma-carboxylation of specific glutamic acid residues that make it possible for calcium binding and allowing the coagulation cascade to occur. Protein C and S are also vitamin K dependent but are opposite from the clotting factors in that they are anticoagulant proteins that help balance the bodies clotting and clot degradation functions. Warfarin functions by antagonizing the action of vitamin K retarding the action of the clotting factors.

Case 4:A 7-year-old African American girl came with swelling in the lower jaw on the left side for the past 2 months. Physical examination revealed a solitary, diffuse swelling measuring approximately 6cm×5cm in size on the left side of the mandible. The surface of the swelling appeared smooth, stretched, and erythematous. On palpation, it was firm in consistency, tender and fixed to the underlying structures. The left submandibular lymph nodes were enlarged, firm and fixed.The laboratory investigations revealed: Increased total white blood cell count; Negative HIV test and elevated serum alkaline phosphatase. Histopathological section of the enlarged left submandibular lymph node showed dysplastic cells arranged in sheets with scanty stroma. Lymphocytes were large and round with scanty cytoplasm and increased nuclear to cytoplasmic ratio. Many abnormal and normal forms of mitoses were evident. Numerous macrophages within the tumor tissue gave a characteristic "starry-sky appearance". Cytogenetic testing revealed t(8;14) aberration. The child was diagnosed to have Burkitt’s lymphoma.Questions:

1. Describe the risk factors, etiology, pathogenic mechanism, altered morphology & physiology, signs and symptoms, basis for signs and symptoms, differential diagnosis, screening and confirmatory investigations including immunophenotyping and cytogenetics, prognosis, and complications of: i) Follicular lymphoma and ii) Burkitt’s lymphoma.

Follicular LymphomaAges Affected: 40-60- Male and Female equal

Translocation: 14; 18 – this will turn on the BCL2 gene to block apoptosis pathway

Markers: CD 19, CD20,BCL 6 CD 10, BCL2

Presents with: Painless lymphadenopaty that can progress beyond the nodes tomarrow and spleen or become a diffuse large B cell Lymphoma which has a poor prognosis

INDOLENT and DIFFICULT TO CURE

HISTO: Looks like normal germinal centers with less mitosis. Evidence of contours and course nuclear chromatin

Survival and prognosis: Median survival is 10 years but can range from anywhere from 1 yr to 20 yrs with some never needing treatment. 5 yr survival rate is 22%

BURKITT’S LYMPHOMA

Ages : Adolescents and young adults

Translocation: 8;14 – this will move the cmyc gene next to the heavy chain Ig gene

Markers: CD 19,CD20, CD 10, IgM

Presents with: Is tied to an infection with the EBV. -involves a growth along the jaw line or other facial bone ( endemic form ( seen in Africa)) or iliocecal jxn (sporadic form) both of which are extremely fast growing and responsive to chemo.

HISTO: Starry Sky appearance with uniform round nuclei and 2-5 nucleoi, with ahigh rate of division

Survival and Prognosis: treatment with rituximab has an 8 yr survival rate of 91%.BL. Responds well to chemo and is cureable

2. Describe the immunology of blood transfusion reactions.

ABO Blood Groups: According to ABO blood system, there are 4 different types of blood groups: Blood Group Antigen on RBC Anti-IgM in

plasma*Comment

A A antigen Anti-B-IgMB B antigen Anti-A-IgMAB A and B antigen No Anti-IgM Universal recipientO Neither A nor B

antigenBoth Anti-A-IgM and Anti-B-IgM

Universal donor

*Note: Common gut bacteria bear antigens that are similar or identical to blood group antigens. This results in formation of antibodies to these antigens in individuals who do not bear a corresponding antigen on their RBC. (Simply put: An individual with Group A blood type who has never been exposed to Type B blood still has Anti-B-IgM due to an antigen identical/similar to RBC B antigen present on gut bacteria). This accounts for the immediate agglutination response that occurs when an individual is presented with incompatible blood transfusion. The outcome is detrimental leading to hemolysis, renal failure, shock and even death.

Rh Antigen: Some people also have Rh antigen on the surface of their RBCsRh+: → have Rh antigen on RBC surface→no Anti-Rh-IgG antibodies Rh-:→ no Rh antigen on RBC surface→can produce Anti-Rh-IgG antibodies if exposed to blood of Rh+ invidiual. Typical example is an Rh- mother giving birth to Rh+ child. This exposure often occurs during birth itself resulting in mom making anti Rh IgG that can cross placenta during subsequent pregnancy causing hemolytic disease of the newborn (the next Rh+ child at risk!)

Note: Anti-AB antibodies (IgM) do not cross placenta Anti-Rh antibodies (IgG) cross placenta

3. What is meant by “chromosomal translocation”? Illustrate this in chronic myeloid leukemia (CML), acute myeloid leukemia (AML), Follicular lymphomas and Burkitt’s lymphoma.

Chromosomal translocation is a transfer of chromosome parts between two nonhomologous chromosomes; translocations can be balanced or unbalanced.

Chronic myeloid leukemia (CML): t(9;22 )translocation of the ABL proto-oncogene. ABL fuses with the break cluster region (BCR) on chromosome 22 (BCR-ABL fusion gene). Chromosome 22 with the translocation is called the Philadelphia chromosome.

Acute myeloid leukemia (AML): In acute promyelocitic leukemia (M3) there is a t(15;17) translocation

Follicular lymphomas: t(14:18)

Burkitt’s lymphoma: A translocation that puts the C-myc oncogene next to a very active promoter such as an immunoglobulin promoter. t(8;14), t(8;22), t(8;2)

GIT

Case 11. Describe etiology, pathogenesis, histopathology, clinical features and complications of peptic ulcer disease.

Gastric Ulcer (25% of ulcer cases) Duodenal Ulcer (75% of ulcer cases)

Etiology 80% of cases caused by H.pylori- NSAIDs

90-95% of cases caused by H.pylori

Pathogenesis Defective mucosal barrier due to H.pylori making it more susceptible to acid; muscosal ischemia, bile reflux, delayed gastric emptying

Defective mucosal barrier due to H.pylori making it more susceptible to acid; increased acid production

Histopathology Gros s : clean, “punched out” margins unlike the raised/irregular margins of carcinomaHisto: Four layers in sequence are noted in histologic sections of ulcers

1. necrotic debris2. inflammation with a predominance of neutrophils3. granulation tissue (repair tissue)4. fibrosis

Clinical Features Epigastric pain exacerbated by eating (weight loss)

Epigastric pain relieved by eating (weight gain)

Complications G.I. bleeding (most common)PerforationRecurrencePatients with H.pylori associated ulcer have increased risk of gastric malignancy

G.I. bleeding (most common)PerforationRecurrenceGastric outlet obstruction, pancreatitisDuodenal ulcers are never malignant

2.Describe the histology of gastric mucosa.

Innermost layer – Mucosa

o Epithelium: Secretory & Absorptive = simple columnar with no goblet cells

o Lamina propria: connective tissue w/ capillaries, gastric glands, GALT -> IgA

o Muscularis mucosa: thin, smooth muscle layer (facilitates discharge of secretions from glands)

– Submucosao Loose connective tissue with large blood vessels and mucus-secreting

glandso Meissner’s Plexus (intrinsic gut motility - 1)

- Muscularis Externao 2 layers: inner circular and outer longitudinalo Fxn: controls lumen size and responsible for peristalsiso Auerbach’s Plexus (second network of neuronal ganglia, intrinsic gut

motility -2, is located between the two layers of muscularis externa)- Serosa

o Mesothelium and loose connective tissueo Surrounds each intestinal loop and then doubles to form the mesentery

within which run blood and lymphatic vessels.

Note: - all GI smooth muscle is connected by gap jxns- extrinsic autonomic innervation: parasympathetic and sympathetic- Sensory fibers go with PNS and mediate visceral reflexes, and hunger, rectal fullness- Visceral pain fibers go with SNS (excessive contraction/ distention of the smooth muscle) and is referred to the body dermatome

More histology….

The stomach has three distinct histological areas:CardiaBody/Fundus Pyloric antrum

Gastric pits- deep invaginations that line the inner surface of the stomach, are closely spaced- lined by mucous-producing cells- penetrate into the thickness of the mucosa and extend to accept the openings of gastric glands

Gastric glands (5 million glands in stomach, secrete 2 L fluid a day)- composed of the following cells: Parietal cells, Chief cells, mucous neck cells, EE cells, and stem cells.- Glands of the cardiac region have no Chief cells and only a few parietal cells- Glands of the pyloric region are very deep, coiled, and possess no Chief cells and only a few parietal cells, contain mainly mucous cells- Glands of the fundic region possess all five cell types (many Chief cells and Parietal cells), extend into the muscularis mucosa, glands are very tightly packed*neither cardiac nor pyloric glands have chief cells-Surrounded by an extensive capillary network to remove the large amount of HCO3- produced while H+ is secreted

Mucus-secreting cells - located on the inner surface of the stomach, in the pit and in the neck, the

transitional region between pits and glands- surface mucus: neutral glycoproteins- neck mucus: acidic glycoproteins- in cardiac and pyloric regions, mucus cells are the major cell type in glands

Parietal cells- located in the upper regions of gastric glands- have numerous elongated tubulovesicles (deep invaginations of the apical

surface) that upon activation fuse with the cell membrane and provide the increased surface area required for additional H+/K+ ATPase for HCl pxn. By doing this, they increase the number of microville that project into the intracellular canaliculi.

- Are larger than Chief cells

Chief cells- located deep in the deep aspect of fundic glands.- secrete pepsinogen stored in granules, have a granular appearance

Enteroendocrine cells - diffuse neuroendocrine system (paracrine)

Region Major Characteristics

Mucosal cell types at surface

Function of Surface Mucosal Cells

Body and Fundus

Rugae: shallow pits; deep glands

Mucus cells (surface)

Chief cells(base)

Parietal cells

Enteroendocrine (EE) cells

Mucus; form protective layer against acid; tight junctions between these cells contribute to the acid barrier of the epithelium

Pepsinogen and lipase precursor

HCl and Infrinsic factor

Peptide hormones

Pylorus Deep pits; shallow, branched glands

Mucous cellsParietal cellsEE cells

Same as aboveSame as aboveHigh [ ] Gastrin

Mention the functions of different cells of gastric mucosa.

Cell type Secretion Action of secretory product

Stimulus for secretion

Inhibitors of secretion

Parietal (oxyntic) cells*Body/Fundus

HCl

Intrinsic factor

Kills pathogensActivates Pepsinogen to Pepsin

Vit. B12 absorption in ileum

GastrinACh (from X)Histamine

Low pH inhibits by inhibiting gastrin)ProstaglandinsChyme in duodenum (via GIP and secretin)

Chief cells*Body/Fundus

Pepsinogen(zymogen)

Converted to pepsin by ↓pH and pepsin (autocatalytic)Digests up to 20% of proteins

ACh (from X)GastrinHCl

H+ (via somatostatin)

G cells*Antrum/ Pylorus

Gastrin ↑HCl secretion (Parietal cells)↑Pepsinogen secretion(Chief cells)↑histamine secretion

-Small peptides, aa, Ca2+ in lumen of stomach-X (via GIP)

H+ (via somatostatin)

by ECL cells -Stomach distention

Mucous cells*Entire stomach

Mucus Forms gel on mucosa to protect mucosa from HCl and pepsin; traps HCO3- to help neutralize acid.

ACh (from X)

3. Describe the cellular mechanism of gastric acid secretion.Physiology

Gastric acid is produced by parietal cells (also called oxyntic cells) in the stomach. Parietal cells contain an extensive secretory network (called canaliculi) from which the gastric acid is secreted into the lumen of the stomach. These cells are part of epithelial fundic glands in the gastric mucosa. The pH of gastric acid is 2 to 3 in the human stomach lumen, the acidity being maintained by the proton pump H+/K+ ATPase. The parietal cell releases bicarbonate into the blood stream in the process, which causes a temporary rise of pH in the blood, known as alkaline tide.

The resulting highly acidic environment in the stomach lumen causes proteins from food to lose their characteristic folded structure (or denature). This exposes the protein's peptide bonds. The chief cells of the stomach secrete enzymes for protein breakdown (inactive pepsinogen and renin). Gastric acid activates pepsinogen into pepsin–this enzyme then helps digestion by breaking the bonds linking amino acids, a process known as proteolysis. In addition, many microorganisms have their growth inhibited by such an acidic environment which is helpful to prevent infection.

Secretion

Gastric acid secretion happens in several steps. Chloride and hydrogen ions are secreted separately from the cytoplasm of parietal cells and mixed in the canaliculi. Gastric acid is then secreted into the lumen of the oxyntic gland and gradually reaches the main stomach lumen.

Chloride and sodium ions are secreted actively from the cytoplasm of the parietal cell into the lumen of the canaliculus. This creates a negative potential of -40 mV to -70 mV across the parietal cell membrane that causes potassium ions and a small number of sodium ions to diffuse from the cytoplasm into the parietal cell canaliculi.

The enzyme carbonic anhydrase catalyses the reaction between carbon dioxide and water to form carbonic acid. This acid immediately dissociates into hydrogen and bicarbonate ions. The hydrogen ions leave the cell through H+/K+ ATPase antiporter pumps.

At the same time sodium ions are actively reabsorbed. This means the majority of secreted K+ and Na+ ions return to the cytoplasm. In the canaliculus, secreted hydrogen and chloride ions mix and are secreted into the lumen of the oxyntic gland.

There are three phases in the secretion of gastric acid:

1. The cephalic phase: 30% of the total gastric acid to be produced is stimulated by anticipation of eating and the smell or taste of food.

2. The gastric phase: 60% of the acid secreted is stimulated by the distention of the stomach with food. Plus, digestion produces proteins, which causes even more gastrin production.

3. The intestinal phase: the remaining 10% of acid is secreted when chyme enters the small intestine, and is stimulated by small intestine distention.

Regulation of secretion

Gastric acid production is regulated by both the autonomic nervous system and several hormones. The parasympathetic nervous system, via the vagus nerve, and the hormone gastrin stimulate the parietal cell to produce gastric acid, both directly acting on parietal cells and indirectly, through the stimulation of the secretion of the hormone histamine from enterochromaffine-like cells (ECL). Vasoactive intestinal peptide, cholecystokinin, and secretin all inhibit production.

The production of gastric acid in the stomach is tightly regulated by positive regulators and negative feedback mechanisms. Four types of cells are involved in this process: parietal cells, G cells, D cells and enterochromaffine-like cells. Besides this, the endings of the vagus nerve (CN X) and the intramural nervous plexus in the digestive tract influence the secretion significantly.

Nerve endings in the stomach secrete two stimulatory neurotransmitters: acetylcholine and gastrin-releasing peptide. Their action is both direct on parietal cells and mediated through the secretion of gastrin from G cells and histamine from enterochromaffine-like cells. Gastrin acts on parietal cells directly and indirectly too, by stimulating the release of histamine.

The release of histamine is the most important positive regulation mechanism of the secretion of gastric acid in the stomach. Its release is stimulated by gastrin and acetylcholine and inhibited by somatostatin.

4. Compare and contrast where stomach contents from a perforation of the posterior, versus the anterior, stomach wall will initially accumulate.

Anterior perforation-peritoneal cavity- patient present with sudden, intense, continuous epigastric pain that spreads rapidly throughout the abdomen often becoming prominent in the right lower quadrant and at times referred to one or both shoulders

Posterior perforation- Pancreas- pain may be intense, persistent and usually referred to the back

5. Describe the blood supply of stomach. List the blood vessels which may be eroded in ulceration of the posterior wall, lesser curvature and greater curvature of the stomach. (Anatomy BRS pg 206, First Aid pg 306)

Arteries Area supplied

1. Left gastric2. Common hepatic3. Splenic arteries

Branch off the CELIAC TRUNK, which arises from the front of the ABDOMINAL AORTA

Supplies derivatives of foregut (lower esophagus, stomach, proximal half of the duodenum, liver, gallbladder, pancreas) and spleen

Splenic via the short gastrics and left gastro-omental/gastroepliploic

Fundus and the greater curvature of the stomach

Common hepatic artery gastroduodenal artery right gastro-omental/ gastroepliploic

Greater curvature of stomach

Common hepatic artery right gastric artery

Runs to the pylorus and the lesser curvature of the stomach and anastomoses with the left gastric artery

Left gastric Lesser curvature of the stomach and the lower esophagus

FYI

Gastroduodenal from the common hepatic via the superior pancreaticoduodenal

Upper duodenum and pancreas

Splenic via the short gastrics and left gastro-omental

Spleen

Proper hepatic Liver, gallbladder, and biliary tree

Ulceration Site Arteries Eroded

posterior wall Splenic artery

lesser curvature Left gastricRight gastric common hepatic artery

greater curvature of the stomach Left gastro-omental/ gastroepliploic and short gastrics splenic

Right gastro-omental/ gastroepliploic gastroduodenal common hepatic

Gastric ulcers may perforate into the lesser sac and erode the pancreas and the splenic artery causing fatal hemorrhage

Duodenal ulcers may erode the pancreas or the gastroduodenal artery (branch off the common hepatic artery) causing burning and cramping epigastric pain, and are three times more common than gastric ulcers

Case 21. Compare and contrast the following aspects of ulcerative colitis and Crohn’sdisease: Etiology, pathogenesis, morphology, organs involved, serology, clinicalfeatures and complications.

Crohn’s disease Ulcerative colitisEtiology -possible: disordered response to

intestinal bacteria (antigenic trigger; ie. mycobacterium paraTB)-No gender preference-Caucasian, Jewish-smoking is risk factor-most cases: 11-35yrs

-possible: autoimmune-No gender preference-More common in Caucasian-14-38yrs-lower incidence in smokers and other nicotine users

Pathogenesis Genetic-HLA-DR7 and DQ4 (30% of N. American males)-NOD2 protein: in Paneth cells; plays a role in host response to bacteriaif defective, chronic infections estbinflamm-defective IL-23R; normally produces IL-17

Genetic-HLA-DRB1-defective IL-23R; normally produces IL-17Immunologic-CD4+: 1° damaging agents

Immunologic:-CD4+: 1° damaging agents-TNF (pathogenic role)

Gross morphology

-thick bowel wall (due to inflamm, submucosal fibrosis) and narrow lumenobstruction-aphthous ulcers in bowel (early)-deep linear ulcers w/ cobblestone pattern-linear fistulas, fissures-fat creeping around serosa

-diffuse ulceration of mucosal surface w/islands of inflamed mucosa (pseudopolyps)-hemorrhage

Microscopic morphology

-noncaseating granulomas (60%) w/in the inflammatory infiltrate of the muscle layer in LI-lymphoid aggregates -deep, linear ulcers-dysplasia or cancer less likely

-ulcers and crypt abscesses containing neutros-no granulomas-dysplasia or cancer may be present

Organs involved/ Extent

-any portion of the GI tract (usually terminal ileum and colon)-skip lesions, rectal sparing

Transmural

-colitis=colon inflammation-continuous colonic lesions always w/rectal involvement (no other part of GI)

Mucosal and submucosalSerology -anemia -anemia

-p-ANCA antibodies in >45%Clinical features

-recurrent right lower quadrant colicky pain (obstruction) w/diarrhea-blood diarrhea only w/colon involvement (fistulas; abscesses)-apthous ulcers in mouth (open sore; canker sore)

-outside GI: erythema nodosum, sacroiliitis (inflamm of sacroiliac joint—d/t HLA-B27 asscankylosing spondylitis), gangrene, iritis (inflamm of iris), migratory polyarthritis

Radiograph: “string” sign in terminal ileum from luminal narrowing by inflammation, fistulas

-recurrent left-sided abdominal cramping w/bloody diarrhea and mucus-fever, tenesmus, weight loss

-outside GI: primary sclerosing cholangitis (chronic liver disease d/t progressive inflamm and scarring of bile ducts inflamm impedes the flow of bile to the gut); erythema nodosum, gangrene, HLA-B27 positive arthritis

Radiograph: “lead pipe” appearance in chronic disease

Complications -strictures, fistualas of intestine -perianal disease-malabsorption nutritional depletion macrocytic anemia

-Malnutrition-toxic megacolon (hypotonic and distended bowel)-colorectal adenocarcinoma

due to vitB12 def-calcium oxalate renal calculi (↑ reabsorption of oxalate through inflamed mucosa)

(risk factors: early onset, duration of disease >10yrs)

2. Determine the lymph nodes that may drain tumors in various parts of the small and large intestine.

Area of body 1° lymph node drainage site

- Stomach Celiac

- Duodenum, Jejunum Superior mesenteric

- Sigmoid Colon Colic inferior mesenteric

- Rectum (lower part),anal canal above pectinate line

Internal iliac

- Anal canal below pectinate line Superficial inguinal

From there it goes to the Thoracic Duct then to Left Subclavian Vein 3. Compare and contrast secretory and osmotic diarrheas. Describe the electrolyte and acid-base imbalances in diarrhea.Secretory- increase in the active secretion, or inhibition of absorption- little to no structural damage. - diarrhea intestinal fluid secretion is isotonic with plasma - continues even when there is no oral food intake.- Ex. cholera Osmotic- too much water is drawn into the bowels. - Diarrhea stops when offending agent (e.g. milk) is stopped.- Ex. malabsorption (e.g., pancreatic disease or celiac disease), osmotic laxatives, lactose intolerance Normal anion gap acidosis: is an acidosis that is not accompanied by an abnormally increased anion gap. Seen in diarrhea.Anion gap = ([Na+]+[K+]) − ([Cl−]+[HCO3−])Electrolyte Profile in blood: ↓ HCO3-, ↑ Cl-, ↓ K+, ↑ Na+

Drop in HCO3− is compensated by an increase in Cl− & the drop in K+ is compensated by a increase in Na+; therefore, anion gap is normal. It is acidosis because you are losing HCO3-.

4. Explain where free air in the peritoneal cavity can accumulate and its clinical importance.

Free air is seen in Sub-diaphragmatic space the uppermost area in the peritoneal cavity

Bowel gas is usually confined to the lumen of the gut, but owing to a variety of pathological processes, gas may escape into the peritoneal cavity. It is important to recognise the radiographic signs of pneumoperitoneum because bowel perforation usually requires surgical intervention.

Caused by :

Perforated peptic ulcer Bowel obstruction Ruptured diverticulum Penetrating trauma Ruptured inflammatory bowel disease (e.g. megacolon) Necrotising enterocolitis/Pneumatosis coli[2] Bowel Cancer Ischemic bowel Steroids After laparotomy After laparoscopy Breakdown of a surgical anastomosis Bowel injury after endoscopy Peritoneal dialysis

5. Describe the development of an ileal (Meckel) diverticulumDirectly from Goljan

1. Meckel diverticulum a. Vitelline (omphalomesenteric) duct remnant

(1) True diverticulum (2) Mnemonic: 2 inches long, 2 feet from ileocecal valve, 2% of

population, 2% symptomatic b. Contains pancreatic rests and heterotopic gastric mucosa

Increase the risk for bleeding

Newborn with fecal material in umbilical area: persistence of vitelline duct

c. Clinical findings

Frontal chest X-ray. The air bubble below the right hemidiaphragm (on the left of the image) is a pneumoperitoneum.

(1) Newborn finding Fecal material in umbilical area due to persistence of vitelline

duct (2) Bleeding (most common finding)

Meckel diverticulum: bleeding most common complication

Common cause of iron deficiency in newborns and young children

(3) Diverticulitis Clinically impossible to distinguish Meckel diverticulitis from

appendicitis

Meckel diverticulitis: mimics acute appendicitis

d. Diagnosis 99mTc nuclear scan identifies parietal cells in ectopic gastric

mucosa. e. Treatment is surgery.

Case 31. Describe the digestion and absorption of lipids in the gastrointestinal tract.DIGESTIONDietary Lipids: Triglycerides, Cholesterol, Phospholipids Stomach (≈10% of lipid digestion)

1. Mixing breaks lipids into droplets→↑ surface area for digestion by pancreatic enzymes

2) Lingual & gastric lipases-initiate lipid digestion by hydrolyzing a very small about of TAGs into glycerol and FAs. 3) Cholesystokinin (CCK) slows gastric emptying →slows delivery of lipids from stomach to duodenum allowing adequate time for digestion and absorption in intestine

Small Intestine (MOST of lipid digestion occurs here)

1. Bile salts emulsify lipids in the SI→↑ surface area for digestion2. Pancreatic Lipases (secreted by pancreas) hydrolyze lipids

o Pancreatic Lipase: TAG→Monoglyceride+2 FAso Cholesterol Ester: Cholesterol Ester→Cholesterol+FA(it also hydrolyzes ester linkages of TAGs yielding glycerol)

- Pholspholipase A2: Pholpholipid→Lysolecithin+FA3) These hydrophobic end products of lipid digestion (all except for glycerol which is hydrophilic) must be solubilized in micellesMicelle:core-hydrophobic products of lipids digestion;exterior- bile salts-amphiphatic

ABSORBTION

1. Micelles come into contact with absorptive surface of epithelial cells→their hydrophobic content diffuses into the cells.

2. In the intestinal cells, the products of lipid digestion are reesterified to TAGs, cholesterol esters, phospholids and form chylomicrons

3. Chylomicrons are transported out of intestinal cells by exocytosis. They are transferred to lymph vessels and enter bloodstream via thoracic duct (do not enter blood stream directly b/c they are too large to enter capillaries)

2. Explain how lactose is digested and absorbed in the gut. List all brush borderenzymes and their functions.Lactose is a disaccharide composed of glucose and galactose. The small intestines cannot absorb dissacharides therefore the -14 glycosidic bond must be broken down by lactase at the brush border. Deficiency of lactase leads to lactose intolerance. The undigested lactose is then metabolized by enteric bacteria which produce large amounts of gases which lead to a range of abdominal symptoms such as cramps, bloating, flatulence, etc… Furthermore, nonabsorbed lactose and water in the lumen of the GI tract can cause osmotic diarrhea. The brush borders of the intestinal lining are the site of terminal carbohydrate digestions. Only monosaccharides are absorbed.

Enzyme Function

Maltase Maltose glucose and glucose

Sucrase Sucrose glucose and fructose

Lactase Lactose glucose and galactose

α -dextrinase Breakdown of dextrin to polymers of D-glucose units linked by α-(1,4) or α-(1,6) glycosidic bonds

Peptidases Proteins amino acids

Enterokinase Trypsinogen trypsin (activates other pancreatic proenzymes)

3) List the enzymes present in pancreatic juice and their role in digestion of lipid,carbohydrate and proteins. Explain the role of cholecystokinin and secretin inaltering composition of pancreatic juice.

Carbohydrates:Pancreatic alpha amylase acts on oligosaccharides and forms disaccharides.Nucleic acids:Pancreatic ribonucleases and pancreatic deoxyribonucleases form oligonucelotides and then nucleosides and finally conversion into free bases, ribose and deoxyribose.Protein:Zymogens consists of trypsin, chymotrypsin, elastase and carboxypeptidases. These are the active degradation enzymes, the inactive forms are secreted by the pancreas, trypsinogen, chymotrypsinogen, proelastase and procarboxypedtidase. Trypsinogen is converted via brush border enzymes (enterokinases) in the intestine into trypsin and converts other zymogens into their active forms. A protective enzyme trypsin inhibitor protein is also secreted to prevent activation of trypsin in the ducsts and pancreas.Functions of the zymogens are as follows:Trypsin – cleaves lysine and arginine residuesChymotrypsin – cleaves large bulky aromatic residuesElastase – cleaves glycine, alanine and serine residuesCarboxypedtidases – cleaves even smaller strands of protein into individual absorbable residuesLipids:Pancreatic secretions in charge of lipid digestion include pancreatic lipase, colipase and phospholipase A, the latter two are also secreted in the inactive forms of procolipase and prophospholipase A. These require activation via cleavage by trypsin.\Pancreatic lipase and colipase - cleaves TAGPhospholipase A – cleaves phospholipids\Secretin and Cholecystokinin are GI hormones that are used to modify contents of the intestine. Secretin is secreted by S cells in the duodenum in response to the acidic contents of the stomach. Secretin increases HCO3- secretion on order to neutralize the acid from the stomach. CCK is

secreted by the I cells in the duodenum and the jejunum in response to increased levels or proteins, nuclei acids and lipids. It increases the pancreatic secretions mentioned above as well as reduce gastric emptying in order to increase the effectiveness for absorbtion.

4. Explain the surgical significance of "McBurney’s point".

A common surface projection of the appendix, which is one-third of the way up along a line from the right anterior superior iliac spine to the umbilicus. If an open laparotomy is preformed McBurney’s point is where a 2-3 inch incision would be made. A more current method of appendectomy is laparoscopic, which involves three 0.25-0.5 inch incisions.

5. Explain the surgical approach through the layers of the abdominal wall toapproach an inflamed appendix and the surgical significance of the muscle fiberorientation.

Perform an open appendectomy starting with incision of the skin (No. 10 Blade). Next, use an (Bovie) electrocautery to incise through the superficial (camper) and deep (Scarpa) fasca. Now the external oblique aponeurosis is exposed and you want to split the external oblique fibers bluntly using (Kelly) clamps or (Roux) retractors. Repeat this splitting and retraction of the internal oblique muscles and the transversus abdominis muscles to expose the transverasalis fascia and the peritoneum. Make a craniocaudal incision in the pericardium with (Metzenbaum) scissors allowing access to the peritoneal cavity. The importance of splitting the muscles along the length of the fibers is to preserve the integrity of the abdominal wall and prevent incisional hernias occurring later as complication of the procedure.

Case 4

1. Describe histological differences in different parts of esophagus. Describe thestructure and functions of upper and lower esophageal sphincters.

The esophagus consists of:-mucosa - contains stratified non-keritinaized squamous cells, lamina propria, and muscularis mucosa (smooth muscle)

-submucosa - mucous secreting glands and connective tissue)

-muscularis externa - this layer varies depending on the area of the esophagus. Upper 1/3 is skeletal muscle, middle 1/3 is mixed skeletal and smooth, bottom 1/3 is smooth muscle.

-adventitia

UES – since it is part of the upper 1/3 of the esophagus, it consists of skeletal muscle and is under conscious contol. Part of the inferior pharyngeal constrictor muscle. The UES opens during swallowing to allow the bolus of food passage into the esophagus.

LES – ring of smooth muscle which opens into the cardia of the stomach. Remains closed except during swallowing and protects from regurgitation of gastric contents back into the esophagus.

2) Explain physiology of swallowing including stages, mechanisms involved, reflex arc, esophageal pressure recordings and timings of opening and closure of upper/lower esophageal sphincters.Swallowing

It is coordinated in the medulla and travels via fibers in the glossopharyngeal and vagus nerves. The sequence is:

1. The nasopharynx closes and breathing is inhibited.2. The laryngeal muscles contract to close the glottis and elevate the larynx3. Peristalsis begins in the pharynx and propels the food bolus toward the esophagus at the

same time, the UES relaxes and the food bolus entersEsophageal MotilityIs based on slow wave contractions of oscillating membrane potentials as dictated by the interstitial cells of Cajal. The Cajal cells are the pace maker of GI contraction and determine the pattern of the action potentials. These slow waves are bring the membrane potential up to -40 mv. At the threshold, the calcium channels open, and the depolarization and contraction can occur. Therefore the rate of slow waves will dictate the rate of action potentials and therefore contraction. The number of action potentials/contractions will vary along the GI tract. It is important to note that neural and hormonal input affect only the frequency of the action potentials, not the frequency of slow waves.Continuing from above, as part of swallowing, the UES relaxes and swallowed food enters the esophagus. The primary peristaltic contraction creates an area of high pressure behind the food bolus and moves the bolus along, constantly contracting behind it. A secondary peristaltic contraction clears any remaning food in the esophagus. As the bolus approaches the LES, it relaxes via vagally meditated VIP. From there the food bolus enters the stomach.Just a note:Depolarization of Circular muscle- leads to contraction of the ring of smooth muscle and a decrease in DIAMETERDepolarization of the Longitudinal Smooth muscle- leads to a decrease in LENGTH.

3. Describe the pathogenetic mechanism, morphology and, signs and symptoms of achalasia and scleroderma (systemic sclerosis) involving esophagus. Achalasia is the failure of the LES to relax d/t loss of Auerbach’s plexus, high LES opening pressure combined with uncoordinated peristalsis. Barium swallow will show dilated esophagus with an area of distal stenosis, bird’s beak appearance. Symptoms will be progressive dysphagia. Systemic scleroderma is a systemic connective tissue disease of autoimmune origin causing an overproduction of collagen. T cells accumulate in the skin and produce cytokines stimulating collagen deposition especially from activation of fibroblasts. In the esophagus it can cause reflux

esophagitis complicated with narrowing of the esophagus, strictures (fibrosis). Also causes decreased motility in the LES causing dysphagia and chest pain.

4. Describe the mechanism for development of megacolon (Hirchsprung’s disease). Development of Hirchsprung’s is caused by failure of neural crest cells to migrate. It is characterized by lack of ganglion cells in the enteric plexus, Auerbach’s and Meissner’s plexuses, in a segment of the colon. This will present as dilation of the colon proximal to the aganglionic segment with severe constipation.

5. Describe the boundaries of the inguinal triangle of Hesselbach and its clinical significance.

The inguinal triangle is bounded by the rectus abdominus muscle medially, the inferior epigastric vessels superior and laterally, and the inguinal ligament inferiorly. Clinically significant because a direct inguinal hernia will protrude through the inguinal triangle.

6) Explain the difference between a direct and an indirect inguinal hernia.INDIRECT INGUINAL HERNIA

Goes INTO the INTERNAL INGUINAL RING, to the external ring and INTO the scrotum

Enters the internal ring lateral to the inferior epigastic artery Occurs in INFANTS due to the process vaginialis failing to close Follows the decent of testes and is covered by all 3 layers of spermatic fascia

DIRECT INGUINAL HERNIA

Goes through the external superficial ring only Protrudes through abdominal wall medial to the inferior epigastric Covered only by external spermatic fascia Older menMDs don’t LieDirect hernia- media to the IEAIndirect hernia- lateral to the IEA

MALE GENITALCase 1Q1. Describe the genetic basis, histopathological findings in the testis, clinical features and the pathophysiological basis for the clinical features in a patient with Klienefelter’s syndrome.Genetic basis: caused by nondisjunction, XXY karyotypeHistophathological findings: testes are largely atrophic, hyalinized seminferous tubules (due to fibrosis), loss of sertoli cells, increased number leydig cells (functionally abnormal, as testosterone is decreased with increased LH and FSH)Clinical features and pathophysiological basis: Infant has usually normal male external genitalia at birth and diagnosis suspected in adolescence.

a. Atrophy of the seminiferous tubules: absence of spermatogenesis, infertility

b. Primary hypogonadism (testosterone deficiency): female secondary sex characteristics at puberty including gynecomastia, soft skin, and female hair distribution

c. Loss of sertoli cells: decreased inhibin causes increased FSH (due to loss of negative feedback with inhibin) increased FSH causes increased synthesis of aromatase in Leydig cells aromatase converts testosterone to estradiol estradiol causes feminization (decreased testosterone)- increased LH (due to loss of negative feedback with testosterone)

d. Higher number of X chromosomes: associated with subnormal intelligence or mental retardation

Q2 Describe the development of the testis, internal genitalia and external genitalia in a male fetus.The gonads are from three sources:

1) mesoderm2) mesenchyme3) primordial germ cells

Begins during the fifth week of life. A bulge in the middle of Mesonephros, gonadal ridge, forms and gonadal cords grow into the mesenchyme. The medulla differentiates into a testis. The SRY gene for the testis-determining factor (TDF) on the short arm of the Y chromosome directs the development of the indifferent gonad into a testis. Fetal testis produces Mullerian-inhibiting substance that suppresses the development of paramesonephric (Mullerian ducts). Primordial germ cells originate in the wall of the umbilical vesicle and migrate along the dorsal mesentery of the gut to the gonadal ridges. During the sixth week the primordial germ cells are incorporated into the gonadal cords and eventually differentiate into sperm. Testosterone stimulates the mesonephric ducts to form male genital ductsMesonephric ducts form:- Ureter- Seminal gland- Ejaculatory duct- Ductus deferens- Efferent ductules and duct of epididymisUrogenital sinus forms:

- urinary bladder- Prostate- Prostatic and penile urethra- Bulbourethral glands

External genitalia are fully differentiated in the 12th week. Proliferating mesenchyme produces a genital tubercle and Labioscrotal swellings and urogenital folds develop on each side. The genital tubercle elongates to form a primordial phallus. As the phallus develops, the urethral folds fuse along the ventral surface of the penis and form the spongy urethra.Labioscrotal swellings fuse to form the scrotum (the line of fusion is the scrotal raphe).Genital tubercle forms the glans of the penis. The corpora cavernosa and and corpus spongiosum develop from mesenchyme in the phallus.

(Before we were born, p. 173-183).

Q3(a) Describe histology of human testis.

1. The capsule of the testis contains three layers. Tunica vaginalis = mesothelium (outer layer) Tunica albuginea = dense regular collagenous CT Tunica vasculosa = thin layer of vascularized loose CT

2. The human testis has a lobular organization. The human testis is subdivided into approximately 250 lobules by septal extensions

from the tunica albuginea. Each lobule contains 1 to 4 seminiferous tubules embedded in a stroma of loose CT

(interstitial connective tissue) which contains blood and lymphatic vessels and macrophages, but lacks typical fibroblasts and other loose CT cells.

The Leydig endocrine cells are located in the interstitial CT.

3. Seminiferous tubules fill most of the volume in the testis. Seminiferous tubules consist of loops (no free ends). Seminiferous tubules are composed of a complex epithelium surrounded by

peritubular "connective" tissue (sometimes called lamina propria). Two major epithelial cell types occur in seminiferous tubules.

(1) Sertoli cells (sustentacular or supporting cells) form a simple tall columnar epithelium (this arrangement is usually not apparent due

to spermatogenic cells) have pale staining cytoplasm which is extensively branched and extends between the

spermatogeneic cells have relatively basally located nuclei which are predominately euchromatic with

prominent nucleoli attach to one another by zonula occludens

(2) Spermatogenic cells Spermatogenic cells are spherical until the later stages of sperm differentiation, then

become very elongated cells. Spermatogenic cells have pale cytoplasm and nuclei which are initially a mixture of

heterochromatin and euchromatin and become heavily heterchromatic during sperm differentiation.

Interconnected clusters of spermatogenic cells are enfolded by Sertoli cells. The spermatogonia which divide to produce the clusters of spermatogenic cells are

enfolded by the basal region of the Sertoli cells. Three clusters of spermatogenic cells (each at a different stage in spermatogenesis)

are typically observed in a given location at one time. The most mature clusters are located closest to the lumen of the seminiferous tubule.

Peritubular "connective" tissue (tunica propria or "lamina propria") surrounds each seminiferous tubule.

A thin basal lamina surrounds the epithelial components of each seminiferous tubule. 3 to 5 layers of myoid cells (smooth muscle-like cells) surround the basal lamina. The myoid cells are interspersed with fine collagen fibers- Rhythmic contractions of

the myoid cells create peristaltic waves that help move spermatozoa and testicular fluid through the seminiferous tubules to the excurrent duct system.

4. Interstitial connective tissue (stromal connective tissue) occurs between seminiferous tubules in the testis.

Testicular interstitial tissue resembles highly vascular loose CT with fine collagen fibers and macrophages, but few or no typical fibroblasts occur.

Interstitial cells of Leydig (Leydig cells) are distributed singly or in small clusters in interstitial stromal tissue.

a. Leydig cells are large cells with pale vacuolated cytoplasm containing extensive sER and occasional crystals of Reinke (refractile crystals of unknown function).

b. Leydig cells have spherical nuclei with both euchromatin and heterochromatin and distinct nucleoli.

Q3(b) Discuss the physiological functions of the Sertoli and Leydig cells. Sertoli cells

Secrete inhibin which inbibit FSH Secrete androgen binding protein (ABP) which maintains levels of testosterone Tight junctions between adjacent Sertoli cells form blood-testis barrier- isolate gametes

from autoimmune attack Support and nourish developing spermatozoa Regulate anti-mullerian hormone

Leydig cells Secrete testosterone

Q3(c) Explain the interrelationship between the Sertoli and Leydig cells and the importance of this regarding male reproductive function

Source: Medical Physiology: Principles for Clinical Medicine, 3rd Edition

Leydig cells do not have FSH receptors, but FSH can increase the number of developing Leydig cells by stimulating the production of growth stimulators from Sertoli cells, which subsequently enhance the growth of the Leydig cells.

In addition, androgens stimulate the proliferation of developing Leydig cells. Estrogen receptors are present on Leydig cells and reduce the proliferation and activity of these cells.

Leydig cells have LH receptors, and the major effect of LH is to stimulate androgen secretion via a cAMP-dependent mechanism. The main product of Leydig cells is

testosterone, but two other androgens of less biological activity, dehydroepiandrosterone (DHEA) and androstenedione, are also produced.

The Sertoli cell is incapable of producing testosterone but contains testosterone receptors as well as FSH-dependent aromatase.

The Leydig cell does not produce estradiol but contains receptors for it, and estradiol can suppress the response of the Leydig cell to LH.

Testosterone diffuses from the Leydig cells, crosses the basement membrane, enters the Sertoli cell, and binds to ABP. As a result, androgen levels can reach high local concentrations in the seminiferous tubules.

Testosterone is obligatory for spermatogenesis and the proper functioning of Sertoli cells. In Sertoli cells, testosterone also serves as a precursor for estradiol production. The daily role of estradiol in the functioning of Leydig cells is unclear, but it may modulate responses to LH.

Case 2 Q1 Risk Factors For Testicular Tumours

1.     White, Family history (Klinefelter’s Syndrome - XXY)

2.     Cryptorchidism increases the risk of germ cell tumors (especially intra-abdominal cryptorchid testis)

3.     Testicular feminization = deficiency of androgen receptors, fetal DHT and Testosterone are unable to function, Mullerian structures absent due to MIF, external genitalia is female, vaginal ends in a blind pouch

4.     Trauma and radiation

5.     Trimodal age distribution

   Q2 Describe histopathological findings in the following tumors of testis:  Seminoma, choriocarcinoma and teratoma.

Testicular Germ Cell Tumors (95%) Testicular non-germ cell tumors (5%)Seminoma = malignant, painless, homogenous testicular enlargement, MOST COMMON testicular tumour affecting males 15 – 35. Large cells in lobules with watery cytoplasm and a “fried egg” appearance similar to koilocytes and oligodendroglioma, radiosensitive, late metastasis, excellent prognosis

Choriocarcinoma = malignant, increased hCG, may ave gynecomastia, disordered syncytiotrophoblastic and cytotrophoblastic elements, hemorrhagic necrosis with sheets of small cuboidal cells with multiple dark pleiomorphic nuclei, hematogenous metastasis to the LUNGS

Teratoma = from somatic cell lines, multiple tissue types (along any cell lineage – skin, cartilage, bone, epithelium), unlike in females, a mature teratoma is

Leydig cell = reinke crystals, androgen producing, gynecomastia, precocious puberty

 

Sertoli cell  = sex cord stroma, benign, visible calcifications, advanced spermatogenesis

 

Testicular lymphoma = COMMON in older men

MALIGNANT

Embryonal carcinoma = painful, worse prognosis, may be associated with an increase in AFP, hCG, large angry looking hyperchromatic nuclei

Yolk sac = common in children up to 3 years, increasedAFP, Schiller-Duval bodies (resemble glomeruli, cancer cells around a vessel)

Q3 Explain the developmental mechanism responsible for the formation ofhypospadias and epispadias.Epispadias: the spongy urethra opens as a groove on the dorsum of the penisHypospadias: the urethra opens on the underside of the penis because of a failure of the two urethral folds to fuse completely. As a result, more urine exits from the underside of the penis than from its tipQ4 Describe histology, nerve supply, blood supply and lymphatic drainage of penis. Histology:

Prepuce (skin above the foreskin)

-retractile fold of skin that contains connective tissue with smooth muscle on its interior

Corpus cavernosa (of the penis and urethra)

-covered by a resistant layer of dense CT (tunica albugenia)-composed of erectile tissue (large # of venous spaces lined with endothelial cells and separated by CT fibers and smooth muscle cells)

Penile urethra -most lined by pseudostratified columnar epithelium-glans penis: becomes stratified squamous epithelium-mucus-secreting glands of Littre throughout

Nerve supply: S2-S4pudendal nervedorsal nerve of penisruns between the two layers of the suspensory ligament of the penisinnervates the skin, prepuce and glans-parasympathetics (arise from the pelvic splanchnic nerves)erection-sympatheticsejaculationBlood supply: abdominal aortacommon iliac vesselsinternal iliacinternal pudendal (runs over superior aspect of the perineal membrane)

first gives off the artery of the bulbsupplies the bulb of the penis and the bulbourethral glandsdeep artery of the penis (terminal branch of internal pudendal)runs through the center of the corpus cavernosum of the penis and supply its erectile tissuedorsal artery of the penispasses through suspensory ligament of the penissupplies the glans and prepuce

Lymphatic drainage: superficial inguinal lymph nodesexternal iliac nodeslumbar (aortic) nodesQ5 Describe synthesis, transport, metabolism and physiological actions of testosterone.SYNTHESIS:-occurs in primarily in the Leydig cells (>95%)

-hypothalamusreleases GnRHacts on anterior pituitaryrelease LHbinds interstial Leydig cells w/LH receptorsLH stimulates cholesterol desmolase

-also occurs in zona reticularis of the adrenal cortex (contain 21 beta hydroxylase and 11-beta hydroxylase so can make glucocorticoids/mineralocorticoids as well)

-17 hydroxylase used here to get to andostenedioneuses 17- hydroxysteroid βdehydrogenase to get to testosterone

-Cholesterol desmolase: rate limiting stepTRANSPORT/PHYSIOLOGICAL ACTIONS:-testosterone released from testislipophilic; binds steroid protein (albumin, sex steroid binding protein)enters the target cell (anywhere but fetal external genitalia; male body, scalp and facial hair; prostate; sebaceous gland)combines directly with the nucleus or converts into dihydrotestosterone first (via 5 alpha hydroxylase)physiological actions

-actions of testosterone: Differentiation of epididymis, vas deferens, seminal vesicles Pubertal growth spurt

Cessation of pubertal growth spurt (epiphyseal closure) Libido Spermatogenesis in Sertoli cells (paracrine effect) Deepening of voice ↑ muscle mass Growth of penis and seminal vesicles Negative feedback on anterior pituitary

-actions of DHT Differentiation of penis, scrotum, prostate Male hair pattern Male pattern baldness Sebaceous gland activity Growth of prostate

METABOLISM:-~7% of testosteroneDHT-~0.3% of testosteroneestradiol (via aromatase in liver and adipose tissues)-testosterone negatively feedsback on the hypothalamus and anterior pituitaryCase 3: Q1-2 Describe pathogenesis, histopathology, clinical features and laboratory findings in a patient with benign prostatic hypertrophy. List the lobes of the prostate and the symptoms most commonly involved in benign prostatic enlargement.Pathogenesis: DHT and ↑ DHT receptors due to age-related ↑ in estradiol causes prostate to

hypertrophy. Hypertrophy compress urethra leading to symptoms. Histopathology: Hyperplastic glands of the middle lobe (transitional zone) lined by tall columnar cells (2 cell layers). Proliferating stroma surrounds glands. Clinical Features: usually > 50 y/o, Voiding symptoms (difficulty in starting and stopping urine flow, reduced flow, dribbling once stopped) then Storage symptoms (frequency,

urgency, nocturia) then Complications (infection, hydronephrosis, dilated bladder)Laboratory Findings: ↑ PSA (usually between 4ng-10ng)Q3 Describe the histology, blood supply and lymphatic drainage of the prostate. Listthe common sites of metastases of carcinoma prostate and give anatomicalbasis for it. Histology:

The prostate is the largest accessory sex gland in men (about 2 × 3 × 4 cm). It contains 30 - 50 tubuloalveolar glands, which empty into 15 - 25 independent excretory ducts. These ducts open into the urethra. The glands are embedded into a fibromuscular stroma, which mainly consists of smooth muscle separated by strands of connective tissue rich in collagenous and elastic fibers. The muscle forms a dense mass around the urethra and beneath the fairly thin capsule of the prostrate.

A characteristic feature of the prostate is the appearance of corpora amylacea in the secretory alveoli. They are rounded eosinophilic bodies. They appear already in the seventh month of foetal development. Their number increases with age - in particular past 50. They may undergo calcification. Corpora amylacea may also appear in semen.

Blood supply:

The main arterial supply to the prostate gland is from the prostatic artery, a branch off of the inferior vesical artery, and it is also supplied by small branches from the middle rectal and pudendal vessels.

Lymphatic drainage: obturator lymph nodes and internal iliac nodes (hypogastric chain)

Prostate Cancer metastasis:

* Bones (spinal column): via Batson’s venous plexus (valveless veins connecting the deep pelvic veins and thoracic veins to the internal vertebral venous plexuses)

Q4 Explain why the common symptoms of prostate cancer usually involve erectileand urinary dysfunction.

Erectile dysfunction can be caused by the treatment of prostate cancer:

· Surgery - may disrupt nerves and blood vessels supplying the penis

· Radiation therapy (develops 6 months post surgery) – damages blood vessels supplying the nerves responsible for erection

· Cryosurgery (freezing of cancerous tissue) – freezing may damage nerves

· Hormone therapy – results in decreased levels of testosterone which affects sex drive and the ability to achieve an erection

Urinary dysfunction can be caused by direct damage to the sphincter or it may result due to instability of the detrusor muscle.

Q5 Describe the nerves that might be compromised during open prostatectomy and the consequence on sexual functioning and urinary continence.Prostatectomy-surgical removal of all parts of the prostate (open prostatectomy=the incision is done below the navel and prostate is removed)Care must be taken to spare pelvic plexus and the two plexuses it gives rise to: prostatic plexus and vesical plexus. Sexual Dysfucnction:Must spare pelvic and prostatic plexusesInferior hypogastric (Pelvic) plexus lies against the posteriolateral pelvic wall, lateral to rectum and base of the bladder. -formed by the union of hypogastric, pelvic splanchnic (contains parasympathetics), and sacral splanchnic (contains sympathetics) nerves. The pelvic plexus gives rise to the prosthetic plexus. The nerves from the prostatic plexus pass to the corpora cavernosa, the erectile tissue of the penis. As a result erection (ruled by parasympathetic nerves S2-S4)

and ejaculation (ruled by sympathetic nerver (L1-L2) can become dysfunctional upon damage of pelvic or prostatic plexuses.Urinary Incontinence:Must spare pelvic and vesical plexusSimilarly to prostatic plexus, vesical plexus also arises from form pelvic plexus. Damage will result in urinary incontinence. Q6 List the target tissues which form dihydrotestosterone from testosterone. Name the enzyme involved. Mention its clinical importance.Testosterone is not active in all androgenic tissues. In some target tissues, dihydrotestosterone (DHT) is the active androgen. In those tissues, testosterone is converted to DHT by 5 -reductaseα . Target Tissues of DHT:

1) Fetal External Genitalia (differentiation of penis, scrotum, prostate) 2) Male body, scalp and facial hairs (male pattern baldness)3) ↑ sebaceous gland activity4) ↑ prostate growth

Clinical importance:1) Congenital 5 -reductase deficiency-ambigous genitalia before puberty (b/c penis, αscrotum and prostate cannot differentiat w/t DHT) but after puberty when testosterone starts increasing→masculinzation and ↑ growth of external genitalia as well as development of secondary male sex characteristics. It becomes evident when that the child is a boy. “Penis at 12” syndrome 2) Since growth of prostate and male pattern baldness depend on DHT rather than testosterone, 5 -reductase inhibitors can be used in treatment of BPH and hair loss in men.α

Case 4: Q1 Define dementia and list the most common causes of dementia in an elderly.

Dementia – the development of memory impairment and other cognitive deficits with preservation of a normal level of consciousness (Robbins)

Major Causes of Dementia:Primary Neurodegenerative Disorders:Alzheimer diseasePick disease and other frontaltemporal degenerationsParkinson disease and diffuse Lewy body degenerationsProgressive supranuclear palsyHuntington disease Motor neuron disease

Also, infections (Prions, HIV, etc…), vascular and traumatic diseases (multi-infarct, subdural hematoma, etc…), metabolic and nutritional diseases, brain tumors, neuronal storage disease and toxic injury.

Q2 List the anatomical areas of the brain involved in Alzheimer’s disease. Relate the signs and symptoms to the anatomical areas involved in a patient involved with Alzheimer’s disease.

The anatomical areas showing a build up of abnormal protein in Alzheimer’s disease are the hippocampus, neocortex, amygdale, basal forebrain, locus ceruleus, raphne nuclei amd entorhinal cortex. Of these areas, the loss of neurons are most noticeable in the hippocampus, the association cortices, some areas of the limbic system as well as the basal nucleus of Meynert.

The most noticeable symptom of Alzheimer patients are their loss of memory and later in the course of disease, the inablilty to work on complex tasks and emotional probelms.The loss of areas that secret neurotransmitters correspond to the changes in mood:Raphne nucleus – serotoninLocus cereleus –norepinephrine Basal nucleus of Meynert – achetylcholineThe loss of memory and emotion corresponds to lesions in the limbic system, and most importantly the hippocampus which establishes long term memory.

Q3Sporadic Alzheimer disease onset is rarely before 50 yrs old. Earlier onset can be seen in heritable forms of Alzheimer disease, which are the minority. From a biochemical and genetic standpoint there is evidence that accumulation of the peptide -amyloidβ (A ) can βinitiate a chain of events leading to the morphologic changes and dementia seen in Alzheimer disease. A is derived from an β amyloid precursor protein (APP) which when cleaved normally by -secretase and -secretase prevents the formation of A . α γ βAlternatively, APP can be cleaved by -site APP-cleaving enzymeβ and -secretaseγ generating A (peptide that accumulates in Alzheimer disease). βGeneration and accumulation of A occurs slowly with advancing age. β Mutations in APP (chromosome 21) or in components of -secretase (presenilin-1 found on γchromosome 14 or presenilin-2 found on chromosome 1) lead to early onset of Alzheimer disease by increasing the rate of A accumulation. Alzheimer disease is seen in βalmost all Down syndrome patients that live past the age of 45. Two genes, Apo 4 and εSORL 1, are thought to be associated with the more common sporadic form of Alzheimer disease. Extracellular accumulation of A causes problems with neuronal function. Aggregates of βA can alter neurotransmission and be toxic to neurons. The presence of A leads to the β βhyperphosphorlation of microtubular binding protein tau. The hyperphosphorylation causes redistribution of tau inside the neuron to form neurofibrillary tangles. This process causes neuronal dysfunction and cell death.Histology: We see extracellular neuritic plaques, which are focal, spherical collections of dilated, tortuous, silver staining neuritic processes around a central amyloid core (Aβ) found in the hippocampus, amygdyla and neocortex. There can also be A without the βneuritic surrounding called disuse plaques. Neurofibrillary tangles (not specific to Alzheimer disease) are bundles of paired helical filaments visible as basophilic fibrillary structures in the cytoplasm of the neurons that displace or encircle the nucleus. A major component of paired helical filament is abnormally hyperphosphorylated forms of the protein tau. These tangles are found in cortical neurons, especially in the entorhinal

cortex, as well as in other sites such as pyramidal cells of the hippocampus, the amygdala, the basal forebrain, and the raphe nuclei

Q4 Define an amyloid. Mention the different types. Describe how the amyloid bodiesare demonstrated in a histological specimen.

Amyloids are extracellular, proteinacious deposits which stain apple-green with Congo Red under polarized light. They all take on a molecular B-pleated sheet structure. This characteristic histological picture is diagnostic for Amyloidosis.

B-Amyloid - derived from Amyloid precursor protein (APP) - Alzheimer's diseaseAL - derived from Ig light chains (Multiple myeloma) - PrimaryAA - derived from serum amyloid-associated protein (SAA) - SecondaryTransthyretin - derived from AF - Senile CardiacAmylin - derived from AE (endocrine) - Type II DiabetesA-CAL - derived from calcitonin - Medullary carcinoma of the thyroidB2-Microglobulin - derived from MHC I - Dialysis Aquired

Q5 Define urinary continence. With the help of a micturition reflex arc, describefactors contributing to the continence and how they are affected in elderly.-Urinary continence is the control of the elimination of urine from the bladder.-The muscles of the bladder, urethra and pelvic floor are under the control of the nervous system. A simplified picture would be that as the bladder fills, sensory receptors in the bladder wall trigger the micturition reflex - a simultaneous contraction of the detrusor and relaxation of the urethral and periurethral muscles. The neurological signals for these actions are co-ordinated by a micturition centre. During voiding afferent pelvic nerve discharges ascend in spinal cord, synapse in pontine micturition centre Descending efferent pathways causeInhibition of pudendal firing - relaxation of sphincter, Inhibition of sypathetic firing - opens bladder neckpelvic parasypathetic firing - detrusor contraction and voiding through urethra.-In elderly pts

Transient urinary incontinence

Transient urinary incontinence is often seen in both elderly and hospitalized patients. The mnemonic DIAPPERS is a good way to remember most of the reversible causes of incontinence

D: Delirium or acute confusion I: Infection (symptomatic UTI) A: Atrophic vaginitis or urethritis P: Pharmaceutical agents P: Psychological disorders (depression, behavioral disturbances)

E: Excess urine output (due to excess fluid intake, alcoholic or caffeinated beverages, diuretics, peripheral edema, congestive heart failure, or metabolic disorders such as hyperglycemia or hypercalcemia)

R: Restricted mobility (limits ability to reach a bathroom in time) S: Stool impaction

Overflow incontinence:The major contributing factor to overflow incontinence is incomplete bladder emptying secondary to impaired detrusor contractility or bladder outlet obstruction. Factors involved in the development of overflow incontinence are physical obstruction such as pelvic organ prolapse and enlarged prostate, and neurological abnormalities, such as spinal cord injuries. It is also commonly associated with bladder neuropathy that occurs in the setting of diabetes mellitus.Patients often complain of continuous small-volume leakage associated with weak urinary stream, dribbling, hesitancy, frequency, and nocturia.Other less frequent causes of urinary incontinence include trauma from pelvic fracture, complications of urologic procedures, and fistulas. In the pediatric population, it includes enuresis and congenital abnormalities of the genitourinary system. Older adults can have transient incontinence from medication, decreased mobility, and fecal impaction.

Q 6:

Osteoporosis- is the reduction in primary trabecular (spongy ) bone mass in spite of normal mineralization. There are two types

Type 1- Seen in postmenopausal women due to increased bone resorption due to decreased estrogen levels.

Type 2- in senile osteoporosis and affects both men and women over the age of 70 equally.

Both cause an increased risk of vertebral crush fractures, acute back pain, loss of height, kyphosis

Osteomalacia- is the defective mineralization of bone. Usually due to a vitamin D def. This will cause a decrease in calcium, and an increase in PTH excretion. It is reversible

Osteoblasts – are responsible for bone formation, by producing osteoid (Type 1 collagen) and allow for mineralizationOsteoclasts- are responsible for bone reabsorption, remove the mineralized matrix and break up the organic bone. As one ages, the osteoblasts don’t fxn as well while the osteoclasts continue to reabsorb.

RENAL

Group 18Group members listed at end

Case 1:1. Describe the contents of the liver segment (include zone1, zone2 and zone3) -

include the structures such as bile ductule, bile canaliculus, sinusoids, Kupffer cell, space of Disse, hepatic artery, portal vein, and central vein.

Refer to p. 308 in First Aid.

A hepatic lobule is a small division of the liver defined on a histological scale. The classical lobule, hepatic lobule, is hexagonal in shape and divided into three zones: Zone 1(periportal zone): encircles the portal triad (hepatic artery, hepatic portal vein and bile ductule) where oxygenated blood from hepatic arteries enter; hepatocytes are specialized for oxidative liver functions (eg. Gluconeogenesis and beta-oxidation)Zone 2 (intermediate zone):Zone 3 (pericentral vein or centrilobular zone): around central vein and where oxygenation is poor, affected 1st by ischemia, contains P-450 system, most sensitive to toxic injury

Each liver cell borders a vascular space, sinusoid, on at least one side and other hepatocytes on its remaining side. The sinusoids drain to the central veins. Where 2 hepatocytes adjoin, they delimit a small intercellular space, bile canaliculus, into which bile is delivered. Since sinusoids are lined by endothelial cells (sinusoidal lining cells) and macrophages (Kuppfer cells), hepatocytes do not come into contact with the bloodstream. Space of Disse intervenes between hepatocytes and sinusoidal cells. This houses microvilli of hepatocytes, occasional fat storing cells (ito cells) and slender reticular fibers that help form the supporting network of the liver.

2.

Explain the biochemical basis for clinical manifestations of deficiencies of vitaminA, D and K in patients with bile duct obstruction.

Vitamins A, D, E, and K are lipid soluble vitamins. Bile duct obstruction results in fat malabsorption and deficiency in fat soluble vitamins.

Vitamin A: Hydroxyl (Retinol), Carboxyl (Retinoic Acid), and aldehyde (retinal).Function:

- Antioxidant- Constituent of visual pigments (retinal and a protein form Rhodopsin, a receptor

for light photons that changes from Trans to Cis-Retinal and results. In the dark, glutamate is continuously released and inhibits the optic nerve bipolar cells. When light activates the Rhodopsin receptor, it hyperpolatizes the rod cell membrane, light stops glutamate release, and the optic nerve is no longer inhibited and sends a signal to the brain.)

- Essential for normal growth, maintenance, and differentiation, of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells) Retinol and retinoic acid bind intracellular receptors (family of Zn finger proteins), and they regulate transcription through specific response elements.

Decifiency:- night blindness- dry skin/ hyperkeratosis

Vitamin D: (D2 = ergocalciferol; D3 = cholecalciferol; 25-OH D3 = storage form; 1,25 –(OH)2 D3 = calcitriol = active form.

Function:- ↑ intestinal absorption of Ca2+ and phosphate - ↑ bone resorption (activates osteoclasts)- Biochem: 1,25-(OH)2 acts on duodenal epithelial cells as a lipid soluble hormone

and binds the intracellular receptor (Zn-finger protein), which binds to response elements in enhancer regions of the DNA to induce the synthesis of calcium binding proteins that are important in stimulating calcium uptake from the GI tract.

Deficiency:- Rickets in children (bending bones)- Osteomalacia in adults (soft bones)- Hypocalcemic tetany

Vitamin K: Function:

- Catalyzes γ-carboxylation of glutamic acid residues (enzyme: -Glutamyl γCarboxylase) on various proteins concerned with blood clotting (clotting factors: II, VII, IX, X, and protein C and S)

- Synthesized by intestinal flora

Deficiency:- Neonatal hemorrhage with ↑ PT and ↑ aPTT but normal bleeding time (neonates

have sterile intestines and are unable to synthesize Vit. K) - Can occur after prolonged use of broad-spectrum antibiotics

First Aid 2010 p. 90, 93, 94.

3. Review the breakdown of heme and excretion of end products of heme degradation in feces and urine. Include the role of UDP glucuronyl transferase in bilirubin metabolism.

(from: Lippincott's Illustrated Reviews: Biochemistry, 4th Edition, pg 283)After approximately 120 days in the circulation, red blood cells are taken up and degraded by the reticuloendothelial system, particularly in the liver and spleen . Approximately 85% of heme destined for degradation comes from red blood cells, and 15% is from turnover of immature red blood cells and cytochromes from extraerythroid tissues.

1. Formation of bilirubin: The first step in the degradation of heme is catalyzed by the microsomal heme oxygenase system of the reticuloendothelial cells. In the presence of NADPH and O2, the enzyme adds a hydroxyl group to the methenyl bridge between two pyrrole rings, with a concomitant oxidation of ferrous iron to Fe3+. A second oxidation by the same enzyme system results in cleavage of the porphyrin ring. The green pigment biliverdin is produced as ferric iron and CO are released [Note: The CO has biologic function, acting as a signaling molecule and vasodilator.] Biliverdin is reduced, forming the red-orange bilirubin. Bilirubin and its derivatives are collectively termed bile pigments. [Note: The changing colors of a bruise reflect the varying pattern of intermediates that occur during heme degradation.]

2. Uptake of bilirubin by the liver: Bilirubin is only slightly soluble in plasma and, therefore, is transported to the liver by binding non-covalently to albumin. [Note: Certain anionic drugs, such as salicylates and sulfonamides, can displace bilirubin from albumin, permitting bilirubin to enter the central nervous system. This causes the potential for neural damage in infants.] Bilirubin dissociates from the carrier albumin molecule and

enters a hepatocyte, where it binds to intracellular proteins, particularly the protein ligandin.

3. Formation of bilirubin diglucuronide: In the hepatocyte, the solubility of bilirubin is increased by the addition of two molecules of glucuronic acid. [Note: This process is referred to as conjugation.] The reaction is catalyzed by microsomal UDP glucuronyl transferase using uridine diphosphate-glucuronic acid as the glucuronate donor. [Note: Varying degrees of deficiency of this enzyme result in Crigler-Najjar I and II and Gilbert syndrome, with Crigler-Najjar I being the most severe deficiency.]

4. Secretion of bilirubin into bile: Bilirubin diglucuronide (conjugated bilirubin) is actively transported against a concentration gradient into the bile canaliculi and then into the bile. This energy-dependent, rate-limiting step is susceptible to impairment in liver disease. [Note: A deficiency in the protein required for transport of conjugated bilirubin out of the liver results in Dubin-Johnson syndrome.] Unconjugated bilirubin is normally not secreted.

5. Formation of urobilins in the intestine: Bilirubin diglucuronide is hydrolyzed and reduced by bacteria in the gut to yield urobilinogen, a colorless compound. Most of the urobilinogen is oxidized by intestinal bacteria to stercobilin, which gives feces the characteristic brown color. However, some of the urobilinogen is reabsorbed from the gut and enters the portal blood. A portion of this urobilinogen participates in the enterohepatic urobilinogen cycle in which it is taken up by the liver, and then resecreted into the bile. The remainder of the urobilinogen is transported by the blood to the kidney, where it is converted to yellow urobilin and excreted, giving urine its characteristic color.

(Diagram and text from Lippincott's Illustrated Reviews: Biochemistry, 4th Edition, pg 282-284)

4.

Describe how ammonia is detoxified in the liver (revise urea cycle). (First Aid 105)The urea cycle (ornithine cycle) produces urea ((NH2)2CO) from ammonia. (NH3). Amino acid catabolism results in the formation of common metabolites (e.g. pyruvate acetyle-CoA), which serve as metabolic fuels. Excess nitrogen (NH4

+) generated by this process is converted to urea and excreted by the kidneys as urea.

Ordinarily Careless Crapper Are Also Frivolous About UrinationOrnithine, Carbamoyl phosphate, Cirtulline, Aspartate, Argininosuccinate, Fumarate, Arginine, Urea

CPS1 = Carbamoyl phosphate synthetaseOTC = Ornithine transcarbamoylaseASS = Argininosuccinate synthaseASL = Argininosuccinate lyase

Reactants Products Catalyzed Location

1 NH4+ + HCO3

− + 2ATP carbamoyl phosphate + 2ADP + Pi CPS1 mt

2 carbamoyl phosphate + ornithine citrulline + Pi OTC mt

3 citrulline + aspartate + ATP argininosuccinate + AMP + PPi ASS cytosol

4 argininosuccinate Arg + fumarate ASL cytosol

5 Arg + H2O ornithine + urea ARG1 cytosolARG1 = ArginaseHyperammonemia = liver disease or hereditary diseases such as ornithine transcarbomoylase (OTC) deficiency lead to an increase in ammonia in the blood which depletes alpha-ketoglutarate and leads to the inhibition of the TCA cycle (Tx: limit protein diet)

Ammonia intoxication = tremor, slurring of speech, somnolence, vomiting, cerebral edema, blurring of vision

5. Name the primary and secondary bile salts. Indicate the rate-limiting enzyme in synthesis of bile salts.

BILE is composed of bile salts (bile acids conjugated to glycine or taurine, making them water soluble), phospholipids, bilirubin, water, and ions. BILE is the only significant mechanism for cholesterol excretion and is needed for the digestion of triglycerides and micelle formation in the small intestine.

Bile salts are bile acids (made by the liver by cytochrome P450 metabolization of cholesterol) conjugated to taurine and glycine. They are stored in the gallbladder. Conjugated bile acids are more efficient at emulsifying fats because at intestinal pH, they are more ionized than unconjugated bile acids.

An important function of bile salts is formation of micelles. This way bile salts keep hydrophobic substances like cholesterol in aqueous solution. In the intestine bile salts are essential to emulsify the lipids. Bile salts are also responsible for absorption of fat-soluble vitamins A, D, E, and K by forming mixed micelles. Bile salts also help in activation of pancreatic lipase. Bile salts act as mild cathartics.

Primary bile acids = cholic acid and chenodeoxycholic acid

Secondary bile acids = formed in the intestine as a result of bacterial action on primary bile acids and these are deoxycholic acid (from cholic acid) and lithocholic acid (from chenodeoxycholic acid)

7 alpha-hydroxylase is the rate-limiting enzyme in the synthesis of bile acid from cholesterol

7 alpha-hydroxylaseCholesterol alpha-hydroxycholesterol

Case 2

1.Describe the anatomical relation between liver, gallbladder, pancreas, small intestine and the connecting ducts.

Image source: http://www.caring4cancer.com/go/liver/basics/what-is-liver-cancer.htm

Anatomical relationship:Liver -surrounded by peritoneum

-attached to diaphragm by coronary and falciform ligaments and the right and left triangular ligaments

Gallbladder -located at the junction of the right ninth costal cartilage and lateral border of the rectus abdominis-lies on inferior surface of the liver between the right and quadrate lobes-in contact with the duodenum and transverse colon

Pancreas -lies largely in the floor of the lesser sac in the epigastric and left hypochondriac regions—forms a major portion of the stomach bed-retroperitoneal (except for a portion of the tail)-head: lies within the C-shaped concavity of the duodenum-unicate process (projection of the lower part of the head): lies behind the superior mesenteric vessels-body: lies behind the stomach-tail: in contact with the spleen (splenic artery runs superior to pancreas, posterior to stomach)

Small intestine (duodenum)

-retroperitoneal (except for the beginning of the first part, which is connected to the liver by the hepatoduodenal ligament)-C-shaped tube surrounds the head of the pancreas

Connecting ducts:-right and left hepatic ducts drain bile from the bile ductules from with in the liverjoin to form common hepatic duct

-bile backs up in to the gallbladder via the cystic duct (passes upward)the cystic duct ultimately joins the common hepatic ductforms the common bile ductcommon bile duct merges with pancreatic duct forms the hepatopancreatic duct (ampulla of Vater)enters the 2nd part of the duodenum at the greater papilla (descending part of duodenum)

Cystic duct Common site for gallstone impactionCommon bile duct -runs behind the first part of the duodenum and through

the head of the pancreas-runs lateral to the proper hepatic artery and anterior to the portal vein in the right free margin of the lesser omentum-sphincter of Boyden: circular muscle layer around the lower end of the duct

Pancreatic duct -begins in the tailruns along the entire pancreas-carries pancreatic juice containing enzymes

Hepatopancreatic duct (ampulla of Vater)

-sphincter of Oddi: circular muscle layer around the duct in the greater duodenal papilla

2.Describe the contents of the hepatoduodenal ligament which will be gripped

during a Pringle maneuver.

Pringle’s maneuver: cross-clamping of the hepatoduodenal ligament containing portal triad (hepatic portal vein, common bile duct, proper hepatic artery) at the foramen of Winslow

-hepatoduodenal ligament: part of the lesser omentum-used for control of hepatic bleeding during liver surgery or donor hepatectomy for living liver transplantation

3. List the 3 common sites where gall stones can be impacted (lodged) and explain the effects of each on the bile flow.

Cystic duct: Causes intermittent biliary colic or acute cholecystitis. Bile flow is only obstructed from the gallbladder, not from liver.

Common bile duct: Causes acute cholecystitis and jaudice. Bile flow is completely stopped.

Ampulla of Vater (Hepaticopancreatic ampulla): Causes acute cholecystitis, jaudice, and acute pancreatitis. Bile flow and pancreatic secretions are completely stopped.

4.List the areas of portal-systemic anastomoses, identify the veins being

connectedand describe how these areas may decompress (alleviate) portal

hypertension.From Essential Clinical Anatomy K. Moore page 174For rapid review the important notes are either highlighted or in bold

Between the esophageal veins draining into ei ther the azygos vein (systemic system) or the left gastric vein (portal system); when di lated these are esophageal varices.

Between the rectal veins , the infer ior and middle veins draining into the IVC (systemic system) and the superior rectal vein cont inuing as the infer ior mesenteric vein (portal system); when abnormal ly di lated these are hemorrhoids.

Paraumbilical veins of the anter ior abdominal wal l (portal system) anastomosing with superficial epigastric veins (systemic system); when di lated these veins produce caput medusae—varicose veins radiat ing from the umbil icus. These di lated veins were cal led caput medusae because of their resemblance to the serpents on the head of Medusa, a character in Greek mythology.

describe how these areas may decompress (alleviate) portal hypertension.

Portal–Systemic AnastomosesThe communicat ions between the portal venous system and the systemic venous system are important cl inical ly in the advent of an intrahepatic or extrahepatic portal venous block. When portal c irculat ion through the l iver is obstructed because of l iver disease or physical pressure from a tumor, for example, blood from the al imentary tract can st i l l reach the r ight side of the heart through the IVC by way of several col lateral

Portal venous system. A. The venous system is demonstrated. B. Portal–systemic anastomoses provide collateral circulation in cases of obstruction in the liver or portal vein. Darker blue, portal tributaries; lighter blue, systemic tributaries; A, anastomoses between esophageal veins; B, anastomoses between rectal veins; C, anastomoses between the paraumbilical veins (portal) and small epigastric veins of the anterior abdominal wall; D, anastomoses between the twigs of colic veins (portal) and the retroperitoneal veins.

routes. These al ternate routes are avai lable because the portal vein and its tributaries have no valves; hence blood can flow in a reverse direction to the IVC.

5.

Explain which caval vein can be anastomosed with the splenic vein to create a portocaval shunt to decompress portal hypertension.

Portal HypertensionWhen scarr ing and f ibrosis from cirrhosis of the l iver obstruct the portal vein, pressure r ises in the portal vein and i ts tr ibutar ies, producing portal hypertension. At the si tes of anastomoses between portal and systemic veins, portal hypertension produces enlarged varicose veins and blood f low from the portal to the systemic system of veins. The veins may become so di lated that their wal ls rupture, result ing in hemorrhage. Bleeding from esophageal varices (di lated esophageal veins) at the distal end of the esophagus is often severe and may be fatal . A common method for reducing portal hypertension is to divert blood from the portal venous system to the systemic venous system by creat ing a communicat ion between the portal vein and the IVC or by joining the splenic and left renal veins—a portacaval anastomosis or portosystemic shunt.

Case 3

1. List the sites of constriction of the ureter and explain their relationship to kidneystones.Obstruction of the ureter is most likely to occurs by renal calculi at the narrowest areas of the ureter where: 1) ureter joins the renal pelvis (ureteropelvic junction)2) ureter crosses the pelvic brim over the distal end of common iliac artery3) ureter enters the wall of the urinary bladder (uterovesicular junction)

2) Identify, in radiological images, the structures in the posterior abdominal wall.

3 Liver (right lobe)8 Rib10 Abdominal Aorta12 Spleen15 Body Of Vertebra19 Head of Pancreas21 Duodenum23 Kidney29 Cauda Equina30 Right Renal Vein31 Small Intestine (Taken from Rohan’s Atlas of Anatomy)

3.

Identify the structures and regions seen grossly in a frontal section of a kidneyand describe their organization and general function.

a) Cortex – contains the renal corpuscle (glomerulus and Bowman’s capsule), and renal tubules except the loop of Henle which enters the renal medulla.

b) Medulla – innermost part of the kidney which splits into a number of sections called renal pyramids. The renal medulla contains the vasa rectae, venule rectae, medullary capillary plexus, the loop of Henle and the collecting tubule.

c) Pyramids – cone shaped tissues of the kidney, the striped appearance is formed by straight parallel segments of nephrons. The base of each pyramid starts at the corticomedullary border and the apex terminates in a papilla, within a minor calyx.

d) Pelvis – the dilated prximal part of the ureter in the kidney. This is the point of convergence of two or three major calyxes. Main function is to funnel the urine into the ureter.

e) Calyx – there are the major and minor calyx. Urine flows through a papilla at the apex into the minor calyx then into the major calyx and finally into the pelvis.

f) Ureter – muscular tubes that propel urine from the kidneys to the urinary bladder.g) Renal artery/vein – carry blood to the kidneys from the abdominal aorta and drain the

kidney to the inferior vena cava.

4.Describe the structure, function and location of each component of a nephronand the urinary tract into which the nephrons empty.

Structure FunctionProximal Tubule Cuboidal epithelial cells with long

microvilliReabsorption of solutes and water. Most reabsorbing occurs here. Some secretion is also involved

Descending thin loop of Henle Squamous epithelial cells Reabsorption of water onlyAscending thin loop of Henle Squamous epithelial cells Reabsorption of solutes onlyThick ascending loop of Henle Cuboidal epithelial cells Resbosorption of solutesDistal convoluted tubule Cuboidal epithelial cells with

short microvilliReabsorption of solutes and also where the macula densa is and therefore senses the GFR

Cortical collecting ducts Cuboidal epithelium Reabsorption of solutes and water. This area also controls the acidity of the urine and blood.

Medullary collecting ducts Cuboidal epithelium Reabsorption of water through aquaporins

5.Describe the components and functions of the juxtaglomerular apparatus.

The juxtaglomerular apparatus consists of afferent arterioles, the modified smooth muscle cells (also called JG cells) and the macula densa. The juxtaglomerular apparatus is used to monitor the GFR. This translates to the blood pressure of the body and therefore maintains blood pressure. The JG cells produce the enzyme called renin and activate the RAS.

6.

Renal agenesis is associated with oligohydramnios (small amount of amniotic fluid) because little or no fluid is excreted into the amniotic cavity. Failure of the metanephric diverticulum (An outgrowth from the mesonephric duct that gives rise to the ureter, renal pelvis, calyces, and collecting tubules; also called uteric bud) to penetrate the metanephrogenic blastema (The mesoderm covering the distal end of the metanephric diverticulum; it gives rise to the nephrons in the permanent kidneys) results in an absence of renal development because no nephrons are induced by the collecting tubules to develop from the metanephrogenic blastema.

Question 7

In a discoid kidney there is complete fusion of the kidneys while in the pelvis. While, in a horseshoe kidney there is only fusion of the inferior poles of each kidneys and the ascending kidneys are stopped when the fused portion reaches the inferior mesenteric artery (pg. 134, 2010 FA; pg. 133 2009 FA)

Case 4

1.

Describe in sequence the tubular segments through which ultrafiltrate flows fromBowman’s capsule to the ureter. Identify the cortical/medullary location of eachrenal tubule segment

There are two types of nephrons, juxtaglomerular and cortical. Cortical nephrons have all portions of its tubule in the cortext except for the loop of henle and collecting duct.

For a juxtaglomerular nephron:

Glomerulus - Cortex (will filter anything under 30Kd or without a strong (-) charge)Proximal Tubule - Cortex (Creatinine, antibiotics, diuretics, uric acid are filtered.   Bicarb, Glucose, AA, NaCl, K, H20 are reabsorbed). Descending tubule - Medulla (Na, K, H20 reabsorbed)Loop of Henle - Medulla (Mg, Ca reabsorbed)Ascending tubule - Medulla (Na reabsorbed)Distal Tubule - Cortex (K, H, Urea filtered, NaCl, Ca, H20 reabsorbed)Collecting duct - Medulla (H20 reabsorbed)Ureter – Pelvis

2.

Renal clearance is the measurement of renal excretion ability. Clearance is a function of glomerular filtration, secretion from the peritubular capillaries to the nephron, and reabsorption from the nephron back to the peritubular capillaries.

Cx = Ux V / Px -Volume of plasma from which the substance is completely cleared - per unit time

Cx = clearance of XUx = Urine concentration of XV = Urine flow ratePx = Plasma concentration of X

Creatinine Clearance (mL/min) =           Urine Creatinine (mg/dL) TotalVolume(mL)           Serum Creatinine(mg/dL) X Time (min)

Reference intervals for corrected creatinine clearances differ between sexes:                    Males:          71 - 135 mL/min/1.73 m2                    Females:      78 - 116 mL/min/1.73 m2

3. Creatinine clearance of the patient is:

192 * 1 / 3.2 = 60

Cx = 60 mL/min

4.

Define and mention the formula to calculate:FILTERED LOAD = GFR X plasma concentrationEXCRETION RATE = V x U(x)

V=Urine Flow RateU(x)= Urine Concentration

NET TUBULAR REABSORPTION RATE=FILTERED – EXCRETEDFiltered = GFR x plasma concentrationExcreted= Urine Flow rate x urine concentrationGiven: GFR, Urine Flow Rate, Plasma and Urine concentrations of a substance.

5) Assuming creatinine clearance is equal to GFR, calculate filtered load of creatinine, urea, sodium and potassium in this patient. Filtered Load= GFR x plasma concentration GFR= 192 mg/dLCreatinine: 192 mg/dL x 3.2 mg/dL=614.4Sodium = 192 md/dL x 142 meq/ LPotassium= 192 x 5.8 meq/LUrea= 192 x 80 mg/dl

CASE 1

Case 1:1. Describe the clinical manifestations of nephrotic syndrome and their pathophysiological

basis. Explain the etiology, pathogenesis, morphological changes, electron microscopy and immunofluorescence microscopy in: i) Minimal change disease and ii) Membranous glomerulonephritis.

Nephrotic syndrome is a glomerular diseases characterized by glomerular injury due to cytokines not neutrophils. The cytokines damage podocytes causing them to fuse together and the negative charge of the GBM is also destroyed. Clinical findings:

a. Key finding is proteinuria >3.5g/24hrsb. generalized pitting edema and ascites – due to hypoalbuminemiac. hypertension – due to sodium renteniond. hypercoaguable state due to loss of antithrombin III – can lead to renal vein thrombosise. hypercholesterolemia – hypoalbuminemia increases synthesis of cholesterol (unknown

mechanism)f. hypogammaglobulinemia – due to loss of gamma-globulins in the urineg. fatty casts with maltese cross and oval fat bodies key finding of nephritic syndrome

Minimal Change Disease Membranous Glomerulonephritis (diffuse membranous glomerulopathy)

Etiology - triggered by recent infection or an immune stimulus- most common in children

- caused by drugs (eg. Captopril), infections (eg. HBV), SLE, and solid tumors (eg. Hodkin’s lymphoma)- most common cause of adult nephritic syndrome

Pathogenesis T-cell cytokins cause the GBM to lose its negative charge; selective proteinuria (albumin, not globulins) due to GBM polyanion loss

Immunologically mediated disease in which immune complexes deposit in the subepithelial spaceAntigen-antibody complexes can develop by the production of immune complexes in situ or by deposition

Morphological changes Structurally normal glomeruli Mesangium is normal, no hypercellularity; Diffuse thickening of membranes

Electron Microscopy Fusion of podocytes and no deposits

“spike and dome” appearance with subepithelial deposits

Immunoflourescence Microscopy

Negative IF Subepithelial ICs with granular IF

Case 1, question 2Trace the circulation of blood through the kidney. Describe in sequence the bloodvessels through which blood flows when passing from the renal artery to the

renal vein, including the glomerular blood vessels, peritubular capillaries andvasa recta.

Renal artery → Interlobar artery → (Arcuate artery) → Interlobular artery → afferent arteriole → glomerular capillaries → efferent arteriole → vasa recta (in the renal medulla) → venulae recta → (arcuate vein) → interlobular vein → interlobar vein → renal vein

(First Aid 2010, p. 458, Netter plate 337)3. Identify the components of the glomerular filtration barrier.

The filtration apparatus enclosed by the parietal layer of the Bowman’s consists of three components;

1. Endothelium of the glomerular capillaries Possess fenestrated capillaries which are larger (70 to 90 nm in diameter), more

numerous, and more irregular in outline than fenestrations in other capillaries Moreover, the diaphragm that spans the fenestrations in other capillaries is absent

in the glomerular capillaries Endothelial cells of glomerular capillaries possess a large number of aquaporin-1

(AQP-1) water channels that allow the fast movement of water through the epithelium

2. Glomerular basement membrane (GBM) A thick (300 t0 350nm) basal lamina that is the joint product of the endothelium

and the podocytes, the cells of the visceral layer of Bowman’s capsule Principal component of the filtration barrier

GBM: size and charge determine protein filtration

a. Composed of type IV collagenb. Size and charge are the primary determinants of protein filtration.

o (1) Heparan sulfate produces the negative charge of the GBM.o (2) Cationic proteins of low molecular weight (LMW) are permeable.o (3) Albumin has a strong negative charge and is not permeable.

Albumin: negative charge; repelled by negatively charged GBM

(a) Loss of the negative charge causes loss of albumin in the urine. (b) Called selective proteinuria (e.g., minimal change disease)

o (4) GBM is permeable to water and LMW (<70,000 daltons) proteins (e.g., amino acids).

c. Causes of GBM thickeningo (1) Deposition of immunocomplexes

Example-membranous glomerulopathyo (2) Increased synthesis of type IV collagen

Example-diabetes mellitus

3. Visceral Layer of Bowman’s capsule

Contain specialized cells called podocytes or visceral cells which extend processes around the glomerular capillaries and secondary processes called pedicels or foot processes

The foot processes interdigitate with foot process of neighboring podocytes and the spaces between them is called filtration slits, which are about 25nm wide and allow the ultrafiltrate from the blood to enter Bowman’s space.

The foot processes contain numerous actin filaments that are thought to help regulate the size and patency of the filtration slits.

a. Fusion of the podocytes: sign of nephrotic syndromeo Serve as a distal barrier for preventing protein loss in the urine

b. Fusion of the podocytes is present in any cause of the nephrotic syndrome

.

4. Compare and contrast the structure and function of cortical and juxtamedullaryNephrons

1. Subcapsular or cortical nephrons Have their renal corpuscles located in the outer part of the cortex They have short loops of Henle extending only into the outer medulla

2. Juxtamedullary nephrons Make up about one eighth of the total nephron count Their renal corpuscles occur in proximity to the base of a medullary pyramid They have long loops of Henle and long ascending thin segments that extend well into

the inner region of the pyramid These structures features are essential to the urine concentrating mechanism .

http://oracle3927.tripod.com/nephron.htm

Case #1: Question 5Alisha Razack

Given the capillary and Bowman’s capsule hydrostatic and oncotic pressures, calculate the net filtration pressure at the glomerular capillaries. Predict the effect on glomerular filtration rate caused by changes in any of these driving forces.(Physiology BRS: pg 158 – 159)

GFR = Kf [(PGC – PBS) – (GC - BS)](GFR is filtration across the glomerular capillaries)(+) net pressure = FILTRATION(-) net pressure = REABSORPTION

Kf is the filtration coefficient = 1 in glomerulus Glomerular barrier consists of capillary endothelium, basement membrane, and filtration slits of

podocytes. Normally, anionic glycoproteins line the filtration barrier and restrict the filtration of

plasma proteins (usually negatively charged). In glomerular disease, anionic charges are removed resulting in proteinuria.

PGC = glomerular capillary hydrostatic pressure which is constant along the length of the capillary. It is increased by dilation of the afferent arteriole (prostaglandins) or constriction of the efferent arteriole (angiotension II) both increased blood flow through the glomerulus. If PGC increases, GFR increases as well.

PBS = Bowman’s space hydrostatic pressure and is analogous to Pi in systemic capillaries. It is increased by constriction of the ureters (ureteral stone). If PBS increases, GFR will decrease.

GC = glomerular capillary oncotic pressure and it normally increases along the length of the capillary because filtration of water increases the protein concentration of the glomerular capillary blood. An increase in GC will decreased GFR

BS = Bowman’s space oncotic pressure. It is usually ZERO because only a small amount of protein is normally filtered. An increase in BS will increase GFR.

Case 2

1)Describe the etiology, pathogenesis, morphology of the glomerular lesion,electron microscopy, immunofluorescence microscopy and clinical features of: i)Poststreptococcal glomerulonephritis ii) Goodpasture’s syndrome.

-both produce nephritic syndrome: proliferation of cells within glomeruli + neutrophilic infiltrationinflammation reaction injures capillariesallows RBCs to leak out; induces hemodynamic changes that cause ↓GFR

-hypertension: d/t ↓ GFR (Na and fluid retention) + ↑ renin release when kidneys become ischemic-periorbital puffiness: d/t Na retention (sometimes edema can be more generalized)-oliguria (~400mL urine/day): d/t ↓GFR from inflamed glomeruli-hematuria: injured capillariesRBCs in urineRBCs dysmorphic w/irregular membranes-RBC casts in urine-mild proteinuria >150mg/day (<3.5g/day)-azotemia: ↑ serum BUN, Cr; BUN:Cr>15; d/t ↓ GFR

Post-streptococcal GN Goodpasture’s syndrome

Etiology -follows Group A strep infection of skin (ie. scarlet fever) or pharynx

-genetic: HLA-BR2 + (80%)-M>F-rare

Pathogenesis Type III hypersensitivity: antibody made against strep (IgG)ag/ab immune complexes formcirculate and deposit beneath podocytes

Type II hypersensitivity: anti-basement membrane antibodies (IgG) against alpha3 chain of collagen in glomerular and pulmonary capillaries

Morphology of glomerular lesion

-diffuse: all glomeruli affected-proliferative (hypercellular glomerulus): d/t proliferation of endo and epi cells w/in glomeruli + neutrophilic infiltration + ↑ mesangial cells

-cresentic (5%): proliferation of parietal epithelial cells in Bowman’s capsuleoccupies ~1/2 the urinary spacecells encase, compress glomerular tuft

Electron microscopy

-electron dense subepithelial depositions -NO electron dense deposits

Immuno-fluorescence microscopy

Granular (irregular immune complex deposits in the capillaries)

Linear (antibodies line up against evenly distributed antigens in BM)

Clinical features -hematuria 1-3 wks post-infection w/a nephritogenic strain (never cause rheumatic fever)-↑ anti-DNase B titers-streptolysin O degraded by skin oils (so anti-b not seen)-usually resolves

-begins with hemoptysis, pulmonary hemorrhage (crackles on P/E)-ends with renal failure-rapidly progressive: acute renal failure over days to weeks-poor prognosis

2. Describe the development of the kidney from the metanephric diverticulum and the metanephric mass of mesoderm.

Metanephric diverticulum (ureteric bud): - Dervied from caudal end of mesonephros- Give rise to ureter, pelvises, calyces, and collecting ducts

Metanephric mass:- Ureteric bud interacts and induces the mass to differentiate- Give rise to glomerulus and renal tubules up to the distal convoluted tubules

3. Explain how changes in plasma flow rate affect glomerular filtration rate.

Renal plasma flow (RPF) is the amount of plasma that perfuses the renal tubules per unit time. Best estimated with para-aminohippuric acid (PAH) clearance. PAH is both filtered and actively secreted.

GFR is the measure of fluid filtered from the renal glomerular capillaries into the Bowman's capsule per unit time. Creatinine clearance is typically used to estimate GFR. Creatinine is filtered and only slightly secreted.

Filteration Fraction (FF) = GFR / RPF. RPF affects GFR differently in different settings (afferent vs. efferent). See table.

Effect RPF GFR FFAfferent arteriole constriction ↓ ↓ ConstantAfferent arteriole dilation ↑ ↑ ConstantEfferent arteriole constriction ↓ ↑ ↑Efferent arteriole dilation ↑ ↓ ↓

4)

Describe the renal transport of following substances in the PCT: glucose,bicarbonate, phosphate, amino acids.

From medical physiology Boron Glucose reabsoption:Secondary active transportLuminal membrane-Cotransport with NaBasolateral membrane -GLUT2Renal threshold =300 mg/dl375 mg/min (TmG) divided by 125 ml/min (GFR)Actual renal threshold = 200 mg/dl

The threshold for glucose is affected by the following:GFR – a low GFR causes an increased threshold because the filtered glucose is

decreased and the kidney can reabsorb the filtered glucose even though the plasma glucose is increased (more time for reabsorption)

TmG – a decreased TmG lowers the threshold because the tubules have a reduced capacity to reabsorb glucose.

Splay – “rounded” as it approaches its maximum which is caused by different nephrons having different reabsorption and filtering capacities.

Amino acid reabsorption• All filtered AAs are reabsorbed in PCT• Luminal membrane

– Cotransport with Na• Basolateral membrane

– Diffusion

Bicarbonate reabsorption:• 90% of filtered is reabsorbed in PCT• Filtered HCO3 + H2O ®H2CO3 • H2CO3 ® H2O + CO2 in the presence of carbonic anhydrase • CO2 diffuses into the cell + H2O®H2CO3 • H2CO3 ® CA ® H + HCO3

• HCO3 is reabsorped H+ is secreted in exchange for Na +

Phosphate reabsorption:• Bones, teeth & skeleton (80%)• Intracellular P (20%)• Plasma P 1mmol/l freely filtered• 1/3 of filtered is excreted in urine• Cotransported with Na• Rate of absorption is under the

control of PTH & VD (¯rate of absorption)• Compete with glucose: blocking glucose ® P reabsorption

5) Describe the renal transport of following substances in the PCT: glucose,bicarbonate, phosphate, amino acids.Early PCT reabsorbs all the glucose and AAs and most phosphate via a coupled cotransport with Na+. In each case, Na moves into the luminal cell and down its electrochemical gradient while glucose, phosphate, AAs move into the cell against their electrochemical gradients.

The HCO3- story is a bit more complex….The only Na+ driven countertranport mechanism in the early PCT is the Na+-H+ antiporter (Na into the luminal cell, H+ into the tubular lumen). In the lumen, H+ combines with filtered HCO3- forming CO2 & H2O→both move from lumen into the luminal cell→ reconverted to H+ & HCO3- (with help of carbonic anhydrase). HCO3- reabsorbed into the blood by facilitated diffusion. Net Result: reabsorbtion of filtered HCO3-

6) Describe the mechanisms for NaCl absorption along the different segments ofthe renal tubule such as PCT, Henle’s loop, distal convoluted tubule andcollecting duct. Summarize the humoral factors which regulate NaCl reabsorptionalong the nephron.

Segment Cellular Mechanism Hormone ActionsEarly proximal tubule Na-glucose (SGL2 tranporter),

Na-AA, Na-phosphate cotransportNa-H+ countertransport

PTH inhibits Na+-phosphate contransport

Late proximal tubule NaCl reabsorbtion driven by Cl Angiotensin II stimulates Na+-

gradient (Note: 2 separate channels Na-H via NHE3 countertranporter and Cl-formate anion countertransport)

H+ exhanger→↑ Na & H2O excretion

Thick Ascending Loop of Henle Na-K-2Cl cotransport (NKCC2 tranporter)

ADH stimulates this cotransprot

Early DCT Na-Cl contransport (NCCT transporter)

PTH-↑ Ca/Na exhange→ ↑Ca reabsorbtion

Collecting Duct Reabsorb Na (ENaC) in exchange for secretion of K (ROMK) & H.

Aldosterone stimulate K & H secreton and Na reabsorbtion

CASE 3.

1. Discuss the causes, pathogenesis, morphological changes and clinical features of acute tubular necrosis.Disease: Acute Tubular Necrosis (ATN)Etiology: Most common cause of acute renal failure

A period of inadequate blood flow to the peripheral organs (i.e. hypotension and shock also blood transfusion mismatch, hemolytic crisis and myoglobinuria) ischemic ATN

Poisons, heavy metals (e.g. mercury), organic solvents (e.g. carbon tetrachloride and drugs (i.e. gentamicin, other antibiotics) and radiographic contrast agents nephrotoxic ATN

Pathogenesis: Tubular injury persistent and severe disturbances in blood flow diminished oxygen and substrate delivery to tubular cells

Loss of cell polarity: epithelial cell detachment, necrosis, granular (“muddy brown”) casts

Morphological Changes:

Ischemic ATN: necrosis of short segments of the tubules usually seen in straight portions of the proximal tubule and ascending thick limbs (“skip lesions”)

Proteinaceous casts in distal tubules and collecting ducts (Tamm-Horsfall protein w/ hemoglobin and plasma proteins)

Interstitium: mild inflammatory infiltrate (PMNs, leukocytes, lymphocytes and plasma cells)

Toxic ATN: similar, necrosis is in proximal tubule

Clinical features: 3 stages: inciting event maintenance (low urine) recovery (2-3) weeks

Initiation (36 hours): inciting event Maintenance (2nd to 6th day): urine output falls, oliguria (50-

400mL per day), signs and symptoms of uremia and fluid overload (patients may die during this phase)

Recovery: steady increase in urine, electrolyte imbalances may occur, about 25% of ATN deaths occur in this phase

2)Explain the distribution of pain from kidney stones that are impacted (lodged) inthe ureter.

There are 3-4 areas that kidney stones are usually lodged at, these would be the uretopelvic junction (UPJ), the top ridge of the ilium, the area where the ureter passes by the iliac arteries and the uretovesico junction (UVJ). The pain that occurs is often described as from loin to groin and follows the general path of the urinary tract, the pain is caused by ureteric peristalisis.

3)Describe the layers that would be cut when harvesting a donor kidney using aposterior approach.

The layers would be :1) Renal Capsule2) Peri-renal fat3) Renal Fascia4) Pare-renal fat5) Tendon of the transversalis muscle6) Latissimus Dorsi muscle7) Skin and Subcutaneous fat

Case 3 - Question 4

Describe the relative resistances of the afferent and efferent arterioles and the effects of selective changes in each on renal blood flow and glomerular filtration.

The vascular resistance in the renal vasculature is controlled at the level of the afferent and efferent arterioles. These arterioles have the largest vascular resistance and hence the largest drop in renal blood pressure occurs at these vessels.

With afferent arteriole constriction there will be a decrease in renal plasma flow (RPF) as well as a decrease in the glomerular filtration rate (GFR) resulting in no change in the filtration fraction (FF = GFR/RPF). With efferent arteriole constriction there will be a decrease iin RPF, but an increase in GFR. As a result, the FF will decrease. ( pg. 458 FA 2010; pg. 438 FA 2009)

5. Identify the two most potent stimuli for ADH release and the negative feedbackmechanism for each. Explain the mechanisms by which ADH causes formation ofconcentrated urine.

A. The most important stimuli for secretion of ADH from the posterior pituitary is increased plasma osmolarity detected by osmoreceptors in the hypothalamus. ADH then acts on collecting ducts by increasing the expression of aquaporin channels. As the filtrate flows down the collecting tubule, the concentration gradient outside the tubule favors water reabsoption (as long as aquaporins are present) and leaves behind concentrated urine. The increase in water content will bring the osmolarity of plasma back to normal, and decrease osmoreceptor firing.

B.A decrease in plasma volume is sensed by baroreceptors in the aortic arch and carotid arteries, which will influence an increase in ADH secretion, and an increase of plasma volume through water reabsorption.CASE 1. Describe four primary acid-base disturbances – Respiratory acidosis and alkalosis, metabolic acidosis and alkalosis. Explain the compensatory changes that take place in each of these conditions.

- Metabolic acidosis dereased pH, decreased Pco2, decreased Bicarbonate- Metabolic alkalosis increased pH, increased Pco2, Increaed Bicarbonate- Respiratory acidosis decreased pH, Increased Pco2, increased Bicarbonate- Respiratory alkalosis increased pH, Decreased Pco2, decreased Bicarbonat

Red primary disturbanceGreen compensatory response

Compensatory Changes-M. Acidosis Hyperventilation-M. Alkalosis Hypoventilation-R. Acidosis Increased renal bicarb reabsorption-R. Alkalosis Decreased renal bicarb reabsorption

2.Draw Davenport diagram showing relationship between arterial pH, arterial

PCO2 and Bicarbonate. Insert points in it to show various acid-base disturbances.

CASE 4

3) Mention primary acid base disturbances in the following conditions. Pg 463- First AidResp. Muscle Paralysis- Resp AcidosisHysterical Hyperventilation-Resp. AlkalosisDiabetic Ketoacidosis-Met AcidosisVomiting-Met AlkalosisHigh altitude-Resp. AlkalosisUpper airway obstruction-Resp acidosisAntifreeze poisioning- Met. AcodidNG tube aspiration-Resp acidosis

4)From arterial blood gas values, id simple and mixed metabolic resp.acid base disturbancesAgain See pg 463 in first aid. They have helpful charts.

pH PCO2 [HCO3-] CompensationMet acidosis Decreased Low low HyperventilateMet alkalosis Increased Increased high hypoventilateResp acidosis decreased Increased Increased Increase HCO3-

reabsResp alkalosis increased decreased Decreased. Decrease renal

HCO3 reabs

Note: the ones in bold are the key changes that dictate the response