Digestive SystemDigestive Glands

Components of Digestive GlandsSmall digestive glands: found in the wall of digestive tractAccessory glands (large digestive glands)Salivary glandsPancreasLiver

General structure of Digestive GlandsParenchyma:(functional portion of an organ) acini/gland cells ductsStroma: (non-functional portion of an organ) capsule CT inside the organ

Salivary Glands

Salivary GlandsGeneral structure of the large salivary glandsParenchymaacinusductSerous acinusMucous acinusSeromucous/mixed acinusIntercalated ductStriated/secretory ductInterlobular ductExcretory duct

Model (structure of the large salivary glands)

Salivary GlandsStructural characteristic of gland cell:Serous acinus: comprised by serous cells. zymogen granules in apical cytoplasm.Mucous acinus: comprised by mucous cells. mucinogen granules in cytoplasm.Seromucous acinus: comprised by both cells./mixed acinus demilume

Serous acinus zymogen granules in apical cytoplasm.

Serous cell:Basal lamina(bl);Connective tissue (ct);Desmosome (d);Endothelium (en);Golgi comples (g);Intercellular space (is);Lumen (l);Microvilli (mi);Mitochondria (m);Nucleus (nu);RER (re);Secretion granule (sg).10.000x

Mucous acinus: mucinogen granules in cytoplasm.

Detail of mucous cells:mucous cell (sc);Golgi complex (gc);Intercellular space (is);Secretion granule (sg);Lumen (l);Nucleus (n);RER (re).10000x.

Seromucous acinus/mixed acinusdemilume

Salivary GlandsAcinusDuctIntercalated duct: Simple squamous/cuboidal epith. Striated/secretory ducts: simple tall columnar epith.Interlobular duct: pseudostratified columnar epith.Excretory ducts: stratified squamous epith.

Salivary GlandsIntercalated duct:Simple squamousor cuboidal epith.

Salivary GlandsIntercalated duct: simple squamous or cuboidal epith.

Detail of intercalated duct cellBasal laminar (bl);Desmosome (d);Nerve fibers (nf);Golgi complex (g);Intercellular space (is);Mitochondria (m);Nucleus (nu);RER (re).13.000x

Salivary GlandsStriated/secretory duct: simple tall columnar epith.

Salivary GlandsStriated /secretory duct

Salivary GlandsStriated/secretory ductThe secretory ducts, which are continuous with intercalated ducts, are wider and lined with a simple columnar epithelium. As the secretion from the acini passed through the secretory ducts, the epithlium can re-absorb sodium (Na+) and water from the lumen to the interstitium and transport potassium (K+) into the saliva, thus changing the consistency of the saliva. The secretory ducts drain into interlobar ducts which run between lobules.

Salivary GlandsInterlobular duct: excretory duct:Pseudostratified columnar epith. Stratified squamous epith.

Salivary glandsIncludeParotid G.Submandibular G.Sublingual G.Function:Moistening food.Carbohydrate digestion.Secrete IgA.

Pancreas The pancreas is a lobular organ. The pancreas has both exocrine functions (releases digestive enzyme secretions into the intestines) and endocrine functions (releases hormones into the blood).

Pancreas

Parenchyma

Parenchyma

Pancreas

Exocrine Pancreas

Exocrine PancreasIt releases the pancreatic juice.Pancreatic juice contain many kinds of enzyme:amylase: hydrolyses starch & glycogen.lipase: hydrolyzes triglycerides into fatty acids and mono-glyceridescholesterol esterase: breaks downtrypsin and chymotrypsin: hydrolyze proteins.ribonuclease & deoxyribonuclease: split nucleic acids.

PancreasEndocrine pancreasIslets of LangerhansScatter throughout the exocrine pancreas.Three types of cells:A-cells (20%) glucagon (glycogen glucose)B-cells (75%) insulinD-cells (5%) somatostatinCapillaries: each islet is richly supplied with blood vessels.

PancreasEndocrine pancreas

GlucagonPurpose:Assist insulin in regulating blood glucose (sugar) in the normal range Action: Forces many cells of the body to release (or produce) glucose (increasing blood sugar) Secreted in response to: Low blood glucose Secretion inhibited by: High blood glucose Disease due to deficient action: Some times nothing, sometimes hypoglycemia Disease due to excess action: Hyperglycemia Tumor called:Glucagonoma InsulinPurpose:Regulate blood glucose (sugar) in the normal range Action: Forces many cells of the body to absorb and use glucose thereby decreasing blood sugar levels Secreted in response to: High blood glucose Secretion inhibited by: Low blood glucose Disease due to deficient action: Diabetes Disease due to excess action: Hypoglycemia Tumor called:Insulinoma.

Liver

LiverGeneral IntroductionThe largest gland (--2% of body weight in adult).respectively receives both venous & arterial blood through the portal v. (--75%) & hepatic A (--25%).CT of capsule extended into the parenchyma, forming classical liver lobules.Functions as an exocrine gland (secreting bile) and other very important roles.

Liver

LiverStructrues of Liver lobule

LiverStructures of Liver lobule

Model of Liver Lobule

LiverStructures of Liver lobulesix-sided prism with a central V. at its center.sheets of hepatocytes (or hepatic plates) extend radially from the central V.sinusoids between hepatic plates.Portal triads (or portal area):In the corner of lobules.

Structures of Liver lobuleLiver

Portal Triads (or Portal Area)LiverDefinition: The area of CT found in the angles where adjacent hepatic lobules meet.Components: CT.+portal triad interlobular A interlobular V interlobular bile duct

Portal Triads (or Portal Area)Liver

Portal Triads (or Portal Area)Liver

SinusoidsLiverDilated anastomosing venules between the hepatic plates.Blood pathway: peripherycentral V.Kupffer cells line in the wall of sinusoids.EM (endothelium of sinusoid) significant gaps; numerous fenestration; incomplete basal lamina.

SinusoidsLiver

TEMSinusoids

Sinusoids

HepatocyteLivertypically large polyhedral cells with large round centrally located nucleus.abundance of organelles relates to its functions: Mitochondria: provide energy RER: protein synthesis SER: bile formation/ metabolism of lipids and hormones/detoxification. Lysosome: defence Microbody: detoxification Inclusions: glcogen particles, lipid droplets and pigments.

HepatocyteLiver

Functions of HepatocyteLiverProduce bile.Degrade glycogen to glucose under regulation of hormones.Involve the blood lipid metabolism.Synthesize the blood plasma proteins: albumin;fibrinogen, and so onDetoxification

Bile CanaliculusLiverDefinition: the tubular space limited by plasma membrane of two adjacent hepatocytes.Structure:LM: network-like structures are seen by silver impregnation.EM: plasma membrane of adjacent hepatocytes forms the wall of bile canaliculi. tight junctions form seals.

Bile Canaliculus

Bile Canaliculus

Perisinusoidal space (Disses Spaces)LiverA space between endothelium & hepatocyte.Be visible under EM.Occupy by numerous microvilli of hepatocytes.Fill with blood plasma.have fat-storing cells (storing fat & vitamin A)A site for substance exchangeBetween the blood & the hepatocytes.

Perisinusoidal space (Disses Space)

Perisinusoidal space (Disses Space)

Sinusoids

LiverThree functional surface on the surface of hepatocyte

LiverBlood Supply

Liver

Liver

Liver

Liver