Chapter 12 The Lymphatic System

1. Chapter 12 The Lymphatic System Biology 110 Tri-County Technical College Pendleton, SC

2. Lymphatic Components • Lymphatic vessels, lymph nodes, & various lymphatic organs and tissues • Has two semi-independent parts • Meandering network of lymphatic vessels • Various scattered lymphoid tissues and organs • Vessels transport fluids that escaped from blood vascular system back to blood • Organs house phagocytic cells/lymphocytes essential in body defense & resistance to disease

3. Lymph System Visual

4. Vessels and “Ebb and Flow” • Vessels pick up excess tissue fluid (lymph) and return it to bloodstream • Lymphatics form one-way system and lymph flows ONLY toward heart • Lymph capillaries spiderweb between tissue cells and blood capillaries in loose CT • Absorb leaked fluid (mostly water & small dissolved proteins • Lymph capillaries remarkably permeable

5. Lymph Flow Visual

6. Vessels, cont. • All lymph vessels drain into 2 large vessels • RIGHT lymphatic duct drains right arm and right side of head and thorax • THORACIC duct drains rest of body • BOTH empty into Subclavian vein on their side of body • Vessels are thin-walled and larger ones have “valves • Is low pressure but pumpless system

7. Lymph System Visual

8. Vessels, cont. • Lymph transported by same mechanisms that aid return of venous blood • Milking action of skeletal muscles and pressure changes in thorax during breathing • Smooth muscle in walls of larger lymphatic vessels contracts rhythmically which helps “pump” lymph • Valves in larger vessels prevent backflow

9. Lymph Nodes • Nodes are located along lymphatic vessels • Lymph filtered as passes through 1000s of nodes • Large clusters found in inguinal, axillary, and cervical regions of body • Nodes may enlarge (become swollen) during active infection • Nodes composed of soft reticular connective tissue

10. We still talking about nodes…? • Macrophages located within nodes • Engulf and destroy bacteria/viruses/foreign substances in lymph before its returned to blood • Plasma cells for antibody production also located in nodes • Collections of lymphocytes (WBC type) also in nodes and respond to foreign substances in lymph stream

11. Nodes, nodes, and nodes • Nodes composed of outer cortex containing collections of lymphocytes called follicles • Follicles have germinal centers = generate plasma cells that release antibodies • Rest of cortical cells = lymphocytes in transit • Inner medulla area contains phagocytic macrophages • Enters cortex of node via afferent lymphatic vesselssinusesexits node at HILUS via efferent lymphatic vessels

12. Node Structure Visual

13. Lymphatic Organs • Spleen, thymus, tonsils, & Peyer’s patches • Spleen located in left hypochondriac region • Filters/cleanses blood of bacteria, viruses, and other debris • Most important function=destroy worn-out RBCs and recycle iron to make hemoglobin • Some iron secreted in bile

14. Organs, cont. • Spleen also stores platelets and acts as blood reservoir (so does liver) • Produces blood in the fetus • In adults, spleen produces only lymphocytes • Meanwhile, back at the ranch, and not wanting to waste space, I am practicing my typing skills, and if I may say so, not doing too badly for a over the hill ex-long haired bearded hippy….

15. Thymus Gland • Functions at peak levels during youth • Is lymphatic mass found in throat overlying heart • Produces the hormone THYMOSIN that functions in programming lymphocytes so they can perform protective roles in body • NOT active during adulthood

16. Say ahh……!!!! • Tonsils are small masses of lymphatic tissue that ring pharynx where they are found in the mucosa • Trap and remove bacteria/other foreign pathogens entering throat • May become swollen and red = tonsillitis • My mom treated with warm salt water gargle, but I have switched to aspirin

17. Peyer’s Patches • Found in walls of small intestines • In ideal location to capture/destroy bacteria that could cause enteritis • Tonsils & Peyer’s patches part of “mucosa-associated lymphatic tissue” (MALT) • Acts as sentinel to protect upper respiratory and the digestive tract from never-ending attacks of foreign matter entering those cavities

18. Lymph Organs Visual

19. Antibodies and more… • B lymphocytes (B cells) produce antibodies and oversee humoral immunity • T lymphocytes (T cells) constitute cell-mediated arm of immunity • Antibodies called Immunoglobulins (Igs) • GMADE • Heavy and light chains; Variable and Constant regions

20. Antibody Visual

21. Antibodies, cont. • IgG is most abundant is ONLY type that can cross placenta • Only IgM and IgG fix complement • IgA found only in mucus (major role in preventing pathogens from gaining entry into body • IgE “troublemaker” involved in allergies

22. What it are…?

23. Antibody Action • Inactive antigens by complement fixation, neutralization, agglutination, and precipitation • Complement fixation and neutralization most important to body function • Complement is chief weapon against cellular antigens (bacteria/mismatched blood cells)

24. Complement Action Visual

25. I know what it is, but how does it work?

26. Acquired Immunity Visual

27. Autoimmune Disorders • Body produces antibodies (autoantibodies) and sensitized T cells that attack and damage its own tissues • Graves disease-thyroid gland produces excess thyroxine • Multiple sclerosis, Myasthenia gravis, Juvenile (I) diabetes mellitus, Systemic lupus erythematosus, Glomerulonephritis, and Rheumatoid arthritis (p. 396)

28. Same Coin but Two Sides