1. The Lymphatic System and Body Defenses

2. Lmphatic System Two major categories Non-specific Immunity
Do not act on a specific antigen or invader, but provides a general defense by acting on anything not itself
Specific Immunity
Recognizes specific threatening agents and targets these agents only

3. The Lymphatic System Consists of two semi-independent parts
Lymphatic vessels- structure
Transports escaped fluids back to the blood-function
Lymphoid tissues and organs- structure
Plays essential roles in body defense and resistance to disease-function

4. Lymphatic Characteristics
Lymph—excess tissue fluid carried by lymphatic vessels
Excess tissue fluid accumulation is called edema
Lymphatic vessels (lymphatics) forms one way system toward the heart
Lymph capillaries- weave between the tissue and the blood capillaries in tissues of the body

5. 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
Fluid is forced along the vessel

6. Relationship of Lymphatic Vessels to Blood Vessels
Figure 12.1

7. Lymphatic Vessels
Figure 12.2a

8. Lymphatic Vessels
Figure 12.2b

9. Lymph
Harmful materials that enter lymph vessels, but can’t enter lymph capillaries
Bacteria
Viruses
Cancer cells
Cell debris
Lymph takes a detour through the lymph nodes to clean it of debris and be examined by immune system.

10. Lymphatic Vessels Lymphatic collecting vessels
Collect lymph from lymph capillaries
Carry lymph to and away from lymph nodes
Return fluid to circulatory veins near the heart
Right lymphatic duct- drains lymph from right arm, right side of head and thorax
Thoracic duct- drains lymph from rest of body

11. Properties of Lymphatic Vessels
One way system towards the heart
No pump
Lymph moves toward the heart
Milking action of skeletal muscle
Rhythmic contraction of smooth muscle in vessel walls

12. Lymphatic Vessels
Figure 12.3

13. 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 (a foreign substance)
Lymphocytes are a type of white blood cells
Swollen glands are actually swollen lymph nodes

14. Lymph Nodes
Figure 12.3

15. Lymph Nodes To Know Cervical Nodes- neck Axillary Nodes- under the arm
Inguinal Nodes- upper femor

16. Lymph Node Structure Most are kidney-shaped and less than 1 inch long
Cortex
Outer part
Contains follicles—collections of lymphocytes
Medulla
Inner part
Contains phagocytic macrophages

17. Lymph Node Structure
Figure 12.4

18. Flow of Lymph Through Nodes
Lymph enters the convex side through afferent lymphatic vessels
Lymph flows through a number of sinuses inside the node
Lymph exits through efferent lymphatic vessels
Fewer efferent than afferent vessels causes flow to be slowed
Lymph passes through several nodes before the cleaning process is complete.

19. Other Lymphoid Organs
Several other organs contribute to lymphatic function
Spleen
Thymus
Tonsils
Peyer’s patches
Only lymph nodes filter lymph

20. Other Lymphoid Organs
Figure 12.5

21. Spleen Located on the left side of the abdomen
Filters blood, not lymph
Destroys worn out blood cells
Most important functon
Forms blood cells in the fetus, hematopoietic site
Acts as a blood reservoir, will release blood during hemorrhaging

22. Thymus Gland
Located low in the throat, overlying the heart in the mediastium
Functions at peak levels only during childhood
Largest during childhood
Can be largely replaced with fat in advanced age
Produces hormones (like thymosin) to program lymphocytes

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

24. Peyer’s Patches Found in the wall of the small intestine
Resemble tonsils in structure
Capture and destroy bacteria in the intestine so they don’t penetrate intestinal wall

25. Mucosa-Associated Lymphatic Tissue (MALT)
Includes
Peyer’s patches
Tonsils
Other small accumulations of lymphoid tissue
Acts as a sentinel to protect respiratory and digestive tracts

26. Body Defenses
The body is constantly in contact with bacteria, fungi, and viruses
The body has two defense systems for foreign materials
Innate (nonspecific) defense system, mechanical barriers
Adaptive (specific) defense system, cellular and chemical
Species Resistance- humans are immune to certain diseases
Immunity—specific resistance to disease

27. Immune System
Figure 12.6

28. Body Defenses Innate defense system (nonspecific defense system)
Mechanisms protect against a variety of invaders
Responds immediately to protect body from foreign materials
Adaptive defense system (specific defense system)
Specific defense is required for each type of invader

29. Innate Body Defenses
Innate body defenses are mechanical barriers to pathogens such as
Body surface coverings
Intact skin
Mucous membranes
Specialized human cells
Chemicals produced by the body

30. Innate Body Defenses
Table 12.1 (1 of 2)

31. Surface Membrane Barriers: First Line of Defense
Skin and mucous membranes
Physical barrier to foreign materials
Also provide protective secretions
pH of the skin is acidic to inhibit bacterial growth
Sebum is toxic to bacteria
Vaginal secretions are very acidic

32. Surface Membrane Barriers: First Line of Defense
Stomach mucosa
Secretes hydrochloric acid
Has protein-digesting enzymes
Saliva and lacrimal fluid contain lysozymes, an enzyme that destroy bacteria
Mucus traps microogranisms in digestive and respiratory pathways

33. Cells and Chemicals: Second Line of Defense
Phagocytes
Natural killer cells
Inflammatory response
Antimicrobial proteins
Fever

34. Cells and Chemicals: Second Line of Defense
Phagocytes
Cells such as neutrophils and macrophages
Neutrophils are usually first to arrive at site of injury
Dead neutrophils are called pus
Engulf foreign material into a vacuole
Enzymes from lysosomes digest the material

35. Phagocytes
Figure 12.7a

36. Microbe adheres to phagocyte
Phagocyte engulfs the particle
Phagocytic vesicle containing microbe antigen (phagosome)
Lysosome
Phagocytic vesicle is fused with a lysosome
Phagolysosome
Microbe in fused vesicle is killed and digested by lysosomal enzymes within the phagolysosome
Lysosomal enzymes
Indigestible and residual material is removed by exocytosis
(b)
Figure 12.7b

37. Microbe adheres to phagocyte
Figure 12.7b, step 1

38. Microbe adheres to phagocyte
Phagocyte engulfs the particle
(b)
Figure 12.7b, step 2a

39. Microbe adheres to phagocyte
Phagocyte engulfs the particle
Phagocytic vesicle containing microbe antigen (phagosome)
Lysosome
(b)
Figure 12.7b, step 2b

40. Microbe adheres to phagocyte
Phagocyte engulfs the particle
Phagocytic vesicle containing microbe antigen (phagosome)
Lysosome
Phagocytic vesicle is fused with a lysosome
Phagolysosome
Lysosomal enzymes
(b)
Figure 12.7b, step 3

41. Microbe adheres to phagocyte
Phagocyte engulfs the particle
Phagocytic vesicle containing microbe antigen (phagosome)
Lysosome
Phagocytic vesicle is fused with a lysosome
Phagolysosome
Microbe in fused vesicle is killed and digested by lysosomal enzymes within the phagolysosome
Lysosomal enzymes
(b)
Figure 12.7b, step 4

42. Microbe adheres to phagocyte
Phagocyte engulfs the particle
Phagocytic vesicle containing microbe antigen (phagosome)
Lysosome
Phagocytic vesicle is fused with a lysosome
Phagolysosome
Microbe in fused vesicle is killed and digested by lysosomal enzymes within the phagolysosome
Lysosomal enzymes
Indigestible and residual material is removed by exocytosis
(b)
Figure 12.7b, step 5

43. Internal Innate Defenses: Cells and Chemicals
Natural killer (NK) cells
Can lyse (disintegrate or dissolve) and kill cancer cells
Can destroy virus-infected cells
Not as picky as lymphocytes which will only react against specific cells

44. Cells and Chemicals: Second Line of Defense
Inflammatory response
Triggered when body tissues are injured
Mast cells release chemicals to attract white blood cells

45. Cells and Chemicals: Second Line of Defense
Inflammatory response
Four most common indicators of acute inflammation
Redness
Heat
Swelling
Pain
Results in a chain of events leading to protection and healing

46. Flowchart of Inflammatory Events
Figure 12.8

47. Cells and Chemicals: Second Line of Defense
Functions of the inflammatory response
Prevents spread of damaging agents
Disposes of cell debris and pathogens through phagocytosis
Sets the stage for repair

48. Cells and Chemicals: Second Line of Defense
Phagocytosis
Neutrophils move by diapedesis to clean up damaged tissue and/or pathogens
Monocytes become macrophages and complete disposal of cell debris

49. Cells and Chemicals: Second Line of Defense
Antimicrobial proteins
Attack microorganisms
Hinder reproduction of microorganisms
Most important
Complement proteins
Interferon

50. Cells and Chemicals: Second Line of Defense
Complement proteins
A group of at least 20 plasma proteins
Activated when they encounter and attach to cells (complement fixation)
Damage foreign cell surfaces, allows water to rush in and cell to burst
Release vasodilators and chemotaxis chemicals, cause opsonization
Chemotaxis- cause macrophages and neutrophils to come to the region
Opsonization- cause outside of foreign cell to become sticky so easier to phagocytise

51. Cells and Chemicals: Second Line of Defense
Figure 12.10

52. Cells and Chemicals: Second Line of Defense
Interferon
Viruses have to invade other cells to reproduce
Cant save themselves, but an infected cell secretes proteins called interferons.
Interferons bind to healthy cell surfaces to interfere with the ability of viruses to multiply

53. Cells and Chemicals: Second Line of Defense
Fever
Abnormally high body temperature
Hypothalamus heat regulation can be reset by pyrogens (secreted by white blood cells)
High temperatures inhibit the release of iron and zinc from the liver and spleen needed by bacteria
Fever also increases the speed of tissue repair by increasing metabolic rate

54. Summary of Nonspecific Body Defenses
Table 12.1 (2 of 2)