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Chapt 20: The Lymphatic and Chapt 20: The Lymphatic and Immune SystemsImmune Systems
GoalsGoals
1.1. Discuss the organization of the Discuss the organization of the lymphatic system, including the lymphatic system, including the vessels, principal lymph nodes, vessels, principal lymph nodes, thymus, and spleenthymus, and spleen
2.2. Explain the relationship between the Explain the relationship between the lymphatic and circulatory systems, and lymphatic and circulatory systems, and the role of lymphoid tissue structures the role of lymphoid tissue structures and lymphocytes in the body’s defenseand lymphocytes in the body’s defense
3.3. An introduction to the Immune SystemAn introduction to the Immune System
Overview of the Overview of the Lymphatic SystemLymphatic System
Includes, vessels, fluid, and nodes Includes, vessels, fluid, and nodes or nonsecreting "glands". or nonsecreting "glands".
Lymphatic vessels convey fluid Lymphatic vessels convey fluid from the periphery to the veins. from the periphery to the veins.
The fluid, The fluid, lymphlymph (=clear water), is (=clear water), is what seeps out of the blood at what seeps out of the blood at the peripheral capillaries. the peripheral capillaries. Composition is similar to Composition is similar to plasma without as much plasma without as much proteinprotein
Fig 20.1Fig 20.1
Overview of the Overview of the Lymphatic SystemLymphatic System
Lymphatic organs or tissues Lymphatic organs or tissues ("glands” is a misnomer) are ("glands” is a misnomer) are filtering areas and arenas of filtering areas and arenas of lymphocyte maturation and lymphocyte maturation and competency.competency.
Accessory to cardiovascular Accessory to cardiovascular system, thus there are two system, thus there are two drainage systems.drainage systems.
Fig 20.1
1.1. Filtration of lymphFiltration of lymph
2.2. Return of leaked fluid Return of leaked fluid to cardiovascular to cardiovascular systemsystem
3.3. ““Education” and Education” and production of immune production of immune system lymphocytessystem lymphocytes
4.4. Transport of digested Transport of digested lipids from small lipids from small intestinal lactealsintestinal lacteals
Major Functions of Major Functions of the Lymphatic the Lymphatic SystemSystem
Lymph CapillariesLymph Capillaries
Thin walled Thin walled endothelium endothelium (no BM) (no BM) with periodic one way with periodic one way valves. In general they valves. In general they parallel veins.parallel veins.
– Usually not visible on Usually not visible on tissue sectionstissue sections
Capillaries converge Capillaries converge into collecting vessels into collecting vessels
Lymph CapillariesLymph Capillaries
Closed ends allow fluid Closed ends allow fluid flow inward onlyflow inward only
– Also bacteria, viruses, Also bacteria, viruses, cancer cellscancer cells
Pick up and recycle Pick up and recycle extra tissue fluid extra tissue fluid
The fluid flows to The fluid flows to lymph nodeslymph nodes
Lymph Lymph CapillariesCapillaries
Everywhere, except for Everywhere, except for CNS, bone marrow, cornea CNS, bone marrow, cornea and cartilage.and cartilage.
(XS fluid in CNS becomes (XS fluid in CNS becomes part of CSF)part of CSF)
Special set of lymph Special set of lymph capillaries in villi of small capillaries in villi of small intestineintestine == LactealsLacteals– Fat AbsorptionFat Absorption– To liverTo liver
Damaged valves or blockedlymph vessels edema
Lymphatic vesselsLymphatic vesselsComparable in structure to capillaries, Comparable in structure to capillaries,
and in turn, veins. Thin walls!and in turn, veins. Thin walls!
Hard to find in a general dissectionHard to find in a general dissection
Lymph capillaries converge to become collecting vessels and end up as eitherThoracic duct or right lymphatic duct
Thoracic (left lymphatic) duct
Left subclavian vein
Right lymphatic duct
Right subclavian vein
Cysterna Chyli
Lymphoid Lymphoid OrgansOrgans
1.1. Lymph NodesLymph Nodes1.1. TonsilsTonsils
2.2. ThymusThymus
3.3. SpleenSpleen
4.4. Bone MarrowBone Marrow1.1. Stem cellsStem cells
1. Lymph Nodes1. Lymph Nodes~ 500 (~ 500 ( 1mm to 25 mm) 1mm to 25 mm)
Bean-shaped with hilus, cortex and Bean-shaped with hilus, cortex and medullamedulla
Several afferent vessels, one efferent Several afferent vessels, one efferent vessel vessel
Function: filterFunction: filter
Popular term “lymph gland” is Popular term “lymph gland” is misnomer. Why?misnomer. Why?
Contain lots of Lymphocytes, Contain lots of Lymphocytes, Macrophages and Plasma CellsMacrophages and Plasma Cells
Clinical application: Swollen lymph Clinical application: Swollen lymph nodesnodes
Fig 23.9
Distribution of LNsDistribution of LNs
Cervical lymph nodes Cervical lymph nodes - drain head and neck- drain head and neck
Axillary lymph nodes Axillary lymph nodes - drain arms and breasts- drain arms and breasts
Popliteal lymph nodes - drain legsPopliteal lymph nodes - drain legs
Inguinal lymph nodes - drain lower limbInguinal lymph nodes - drain lower limb
Thoracic lymph nodes - drain thoracic visceraThoracic lymph nodes - drain thoracic viscera
Abdominal lymph nodes - drain pelvic regionAbdominal lymph nodes - drain pelvic region
Intestinal and mesenteric lymph nodes - drain Intestinal and mesenteric lymph nodes - drain abdominal visceraabdominal viscera
TonsilsTonsils
Simple lymphoid Simple lymphoid organs organs – ““Lymph nodules”Lymph nodules”
In the mouth/pharynxIn the mouth/pharynx– Lingual tonsil on Lingual tonsil on
posterior aspect of posterior aspect of tonguetongue
– Palatine = adenoids, Palatine = adenoids, lateral pharynxlateral pharynx
– Tubal, behind Tubal, behind Eustachian TubesEustachian Tubes
Fig 21.3a, page Fig 21.3a, page 584584
Lymphoid TissueLymphoid Tissue
Connective tissue is loaded with Connective tissue is loaded with lymphocyteslymphocytes
Lymphoid nodules Lymphoid nodules are are unencapsulatedunencapsulated clusters of clusters of lymphocytes (lymphocytes ( ~ 1mm). Found ~ 1mm). Found beneath epithelial lining of beneath epithelial lining of respiratory, digestive & urinary respiratory, digestive & urinary tracts, etc.tracts, etc.
Mucosa Associated Lymphatic Tissue Mucosa Associated Lymphatic Tissue (MALT) in GI tract(MALT) in GI tract– 5 tonsils5 tonsils– aggregate lymphoid nodules in aggregate lymphoid nodules in
small intestine (= Peyer’s small intestine (= Peyer’s patches)patches)
– appendix - walls contain lymphoid appendix - walls contain lymphoid tissuetissue
= adenoids
2. 2. ThymusThymus
Location above heart, posterior to sternumLocation above heart, posterior to sternum
Divided into lobulesDivided into lobules
Only lymphoid organ that does NOT fight Only lymphoid organ that does NOT fight antigens, it functions as “T-cell academy” antigens, it functions as “T-cell academy”
Involution after pubertyInvolution after puberty
Epithelial cells produce thymic hormones, Epithelial cells produce thymic hormones, thymosin and thymopoetinthymosin and thymopoetin
3. 3. SpleenSpleen
Largest lymphoid organ, located in LUQ
Soft and very blood rich
Red pulp sinusoids containing RBCs
white pulpwhite pulp lymphoid tissue
Major Functions:
1. Initiation of Immune response to antigens in blood
2. Removal of aged and defective RBCs, Fe salvaging
3. Reservoir for new RBCs
4. Bone Marrow4. Bone Marrow
Mostly in red marrowFrom pluripotent stem cells
Fig 23.7
Bone Marrow: Bone Marrow: LymphopoiesisLymphopoiesis
Lymphocytes are also Lymphocytes are also produced in thymus, produced in thymus, spleen and tonsilsspleen and tonsils
Important example: Axillary Drainage
Drainage from breast and arm
The Immune SystemThe Immune System
Neutrophil with Bacillus anthracis
The primary defense against The primary defense against diseasedisease– Infectious, especiallyInfectious, especially– SpecificSpecific
Centered around the activity Centered around the activity of lymphocytesof lymphocytes– Other cells, too.Other cells, too.
LymphocytesLymphocytes
Agranulocytes - large nuclei and small amount of Agranulocytes - large nuclei and small amount of cytoplasm cytoplasm
Function in identification and inactivation/destruction Function in identification and inactivation/destruction of pathogensof pathogens
Types of LymphocytesTypes of Lymphocytes1.1. T CellsT Cells - cellular immunity - specific for previously - cellular immunity - specific for previously
identified pathogens. AKA “cytotoxic cells.”identified pathogens. AKA “cytotoxic cells.”
2.2. B CellsB Cells - humoral immunity – become plasma cells, - humoral immunity – become plasma cells, which produce antibodies specific to the antigen or which produce antibodies specific to the antigen or pathogen; memory cells for future exposurespathogen; memory cells for future exposures
3.3. NK (Natural Killer) cellsNK (Natural Killer) cells - non-specific, provide - non-specific, provide immunological surveillance, recognition of “non-self”immunological surveillance, recognition of “non-self”
Antibodies (Ab)Antibodies (Ab)
AKA immunoglobulins (Ig)AKA immunoglobulins (Ig) Proteins produced by plasma Proteins produced by plasma
cells in response to a specific cells in response to a specific antigen (Ag)antigen (Ag)– Plasma cells are derived from B-Plasma cells are derived from B-
lymphocyteslymphocytes Antibodies [Ab] frequently Antibodies [Ab] frequently
measured as a diagnostic toolmeasured as a diagnostic tool– SerologySerology
IgG
5 subclasses of Igs:5 subclasses of Igs:
1.1. IgG: main Ab (75%) in serum; + IgG: main Ab (75%) in serum; + main Ab during 2main Ab during 2oo response response
2.2. IgAIgA: main Ab in external secretions: main Ab in external secretions
3.3. IgE: main Ab in allergic reactionsIgE: main Ab in allergic reactions
4.4. IgMIgM: Ab on virgin B-cells; + main Ab : Ab on virgin B-cells; + main Ab during 1during 1oo response response
5.5. IgD: Ab on virgin B-cellsIgD: Ab on virgin B-cells
Sunset on the Atlantic Ocean