Unit 11 Lymphatic System
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The lymphatic system consists of lymphatic vessels and lymphoid tissues that work together to transport fluids and defend the body. Lymphatic vessels carry lymph fluid away from tissues and return it to the bloodstream. Lymph nodes filter the lymph and contain defense cells that fight pathogens. Other lymphoid organs that help fight infection include the spleen, thymus, tonsils, and Peyer's patches in the intestines. The lymphatic system works with the nonspecific and specific immune systems to provide both immediate and targeted defenses against foreign substances that enter the body.
Unit 11 Lymphatic System
- 4. THE LYMPHATIC SYSTEM • Consists of two semi-independent parts – Lymphatic vessels – Lymphoid tissues and organs • Lymphatic system functions – Transport fluids back to the blood – Play essential roles in body defense and resistance to disease ANATOMY h_noveno@hotmail.com 4
- 5. LYMPHATIC CHARACTERISTICS • Lymph – excess tissue fluid carried by lymphatic vessels • Properties of lymphatic vessels – One way system toward the heart – No pump – Lymph moves toward the heart • Milking action of skeletal muscle • Rhythmic contraction of smooth muscle in vessel walls ANATOMY h_noveno@hotmail.com 5
- 6. LYMPHATIC VESSELS • Lymph Capillaries – Walls overlap to form flap-like minivalves – Fluid leaks into lymph capillaries – Capillaries are anchored to connective tissue by filaments – Higher pressure on the inside closes minivalves • Lymphatic collecting vessels – Collects lymph from lymph capillaries – Carries lymph to and away from lymph nodes ANATOMY h_noveno@hotmail.com 6
- 8. LYMPHATIC VESSELS Lymphatic collecting vessels •Collects lymph from lymph capillaries •Carries lymph to and away from lymph nodes •Returns fluid to circulatory veins near the heart •Right lymphatic duct •Thoracic duct ANATOMY h_noveno@hotmail.com 8
- 9. LYMPH • Materials returned to the blood – Water – Blood cells – Proteins • Harmful materials that enter lymph vessels – Bacteria – Viruses – Cancer cells – Cell debris ANATOMY h_noveno@hotmail.com 9
- 10. LYMPH NODES • Filter lymph before it is returned to the blood • Defense cells within lymph nodes – Macrophages – engulf and destroy foreign substances – Lymphocytes – provide immune response to antigens ANATOMY h_noveno@hotmail.com 10
- 12. LYMPH NODE STRUCTURE • Most are kidney-shaped, less than 1 inch long • Cortex – Outer part – Contains follicles – collections of lymphocytes • Medulla – Inner part – Contains phagocytic macrophages ANATOMY h_noveno@hotmail.com 12
- 14. OTHER LYMPHOID ORGANS • Several other organs contribute to lymphatic function – Spleen – Thymus – Tonsils – Peyer’s patches ANATOMY h_noveno@hotmail.com 14
- 15. THE SPLEEN • • • • • Located on the left side of the abdomen Filters blood Destroys worn out blood cells Forms blood cells in the fetus Acts as a blood reservoir ANATOMY h_noveno@hotmail.com 15
- 19. THE THYMUS • Located low in the throat, overlying the heart • Functions at peak levels only during childhood • Produces hormones (like thymosin) to program lymphocytes ANATOMY h_noveno@hotmail.com 19
- 23. TONSILS • Small masses of lymphoid tissue around the pharynx • Trap and remove bacteria and other foreign materials • Tonsillitis is caused by congestion with bacteria ANATOMY h_noveno@hotmail.com 23
- 25. MUCOSA-ASSOCIATED LYMPHATIC TISSUE (MALT) • Includes: – Peyer’s patches – Tonsils – Other small accumulations of lymphoid tissue • Acts as a sentinal to protect respiratory and digestive tracts ANATOMY h_noveno@hotmail.com 25
- 26. PEYER’S PATCHES • Found in the wall of the small intestine • Resemble tonsils in structure • Capture and destroy bacteria in the intestine ANATOMY h_noveno@hotmail.com 26
- 28. BODY DEFENSES • The body is constantly in contact with bacteria, fungi, and viruses • The body has two defense systems for foreign materials 1. Nonspecific defense system • Mechanisms protect against a variety of invaders • Responds immediately to protect body from foreign materials 2. Specific defense system • Specific defense is required for each type of invader • Also known as the immune system ANATOMY h_noveno@hotmail.com 28
- 30. NONSPECIFIC BODY DEFENSES • Body surface coverings – Intact skin – Mucous membranes • Specialized human cells • Chemicals produced by the body ANATOMY h_noveno@hotmail.com 30
- 31. SURFACE MEMBRANE BARRIERS – FIRST LINE OF DEFENSE • The skin – Physical barrier to foreign materials – pH of the skin is acidic to inhibit bacterial growth • Sebum is toxic to bacteria • Vaginal secretions are very acidic • Stomach mucosa – Secretes hydrochloric acid – Has protein-digesting enzymes • Saliva and lacrimal fluid contain lysozyme • Mucus traps microogranisms in digestive and respiratory pathways ANATOMY h_noveno@hotmail.com 31
- 32. DEFENSIVE CELLS • Phagocytes (neutrophils and macrophages) – Engulfs foreign material into a vacuole – Enzymes from lysosomes digest the material ANATOMY h_noveno@hotmail.com 32
- 33. DEFENSIVE CELLS • Natural killer cells – Can lyse and kill cancer cells – Can destroy virus- infected cells ANATOMY h_noveno@hotmail.com 33
- 34. INFLAMMATORY RESPONSE - SECOND LINE OF DEFENSE • Triggered when body tissues are injured • Produces four cardinal signs – Redness – Heat – Swelling – Pain • Results in a chain of events leading to protection and healing • ANATOMY h_noveno@hotmail.com 34
- 35. DEVELOPMENTAL ASPECTS OF THE LYMPHATIC SYSTEM AND BODY DEFENSES • Except for thymus and spleen, the lymphoid organs are poorly developed before birth • A newborn has no functioning lymphocytes at birth; only passive immunity from the mother • If lymphatics are removed or lost, severe edema results, but vessels grow back in time ANATOMY h_noveno@hotmail.com 35