1. The Lymphatic System and Body Defenses
Ms. Dunishiya de Silva

2. Waugh, A. & Grant, A., anatomy and Physiology in Health and Illness 9th Ed (Edinburgh: Churchill Livingstone, 2003) Fig 6.1 “A. The lymphatic system.” P 130

3. The Lymphatic System Lymphatic system functions
Transport excess interstitial fluids (and proteins) back to the blood
Transporting dietary fats.
Play essential roles in body defense and resistance to disease

4. Lymphatic Vessels Lymph Capillaries
Walls overlap to form flap-like minivalves
Fluid leaks into lymph capillaries
Figure 12.2

5. Lymphatic Vessels Lymph Capillaries
Capillaries are anchored to connective tissue by filaments
Higher pressure on the inside closes minivalves

6. Lymphatic Vessels Lymphatic collecting vessels
Collects lymph from lymph capillaries
Carries lymph to and away from lymph nodes
Figure 12.1

7. Lymphatic Vessels Lymphatic collecting vessels (continued)
Returns fluid to circulatory veins near the heart
Right lymphatic duct
Thoracic duct

8. Movement of lymph towards the heart
This is aided by:
Valves in the vessel walls
Milking action of skeletal muscle
Pressure changes in the chest during breathing
Rhythmic contraction of smooth muscle in vessel

9. Lymph
Materials returned to the blood
Water
Blood cells
Proteins

10. Lymph Harmful materials that enter lymph vessels Bacteria Viruses
Cancer cells
Cell debris

11. Lymph Nodes
Figure 12.3

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

13. Lymph Node Structure
Figure 12.4

14. 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

15. Other Lymphoid Organs
Several other organs contribute to lymphatic function
Spleen
Thymus
Tonsils
Peyer’s patches
Figure 12.5

16. 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

17. Herlihy, B. & Maeblus, N K. , The Human Body in Health and Illness (St
Herlihy, B. & Maeblus, N K., The Human Body in Health and Illness (St. Louis: Elsevier Science, 2003) Fig 17-7 “Spleen, composed of white pulp and red pulp” P 328

18. The Thymus
Located in the upper thorax behind the sternum and below the thyroid gland
Functions at peak levels only during childhood
Produces hormones (like thymosin) to program lymphocytes

19. Tonsils Small masses of lymphoid tissue around the pharynx
Trap and remove bacteria and other foreign materials
Tonsillitis is caused by congestion with bacteria

20. Peyer’s Patches Found in the wall of the small intestine
Resemble tonsils in structure
Capture and destroy bacteria in the intestine

21. 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

22. Antigens (Nonself)
Any substance capable of exciting the immune system and provoking an immune response
Examples of common antigens
Foreign proteins
Nucleic acids
Large carbohydrates
Some lipids
Pollen grains
Microorganisms

23. Self-Antigens Human cells have many surface proteins
Our immune cells do not attack our own proteins
Our cells in another person’s body can trigger an immune response because they are foreign
Restricts donors for transplants

24. Antibody - A blood protein produced in lymphoid tissue that can provide immunity against a specific antigen
Pathogen – a disease causing microorganism (e.g. some bacteria, fungi, viruses, etc)

25. First line of defense
Herlihy, B. & Maeblus, N K., The Human Body in Health and Illness (St. Louis: Elsevier Science, 2003) Fig 18-1 “Nonspecific immunity” P 333

26. 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

27. Surface Membrane Barriers – First Line of Defense
Stomach mucosa
Secretes hydrochloric acid
Has protein-digesting enzymes
Saliva, perspiration and lacrimal fluid contain lysozyme
Mucus traps microogranisms in digestive and respiratory pathways

28. Surface Membrane Barriers – First Line of Defense
Cilia sweep dust and bacterial laden mucus towards the mouth
Flow of urine cleanses the urethra
Reflexes assist in the removal of pathogens:-
Coughing and sneezing (the respiratory tract)
Vomiting and diarrhea (the gastrointestinal tract)

29. Defensive Cells Phagocytes Engulfs foreign material into a vacuole
Enzymes from lysosomes digest the material
Figure 12.7a

30. Events of Phagocytosis
Figure 12.7b

31. 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

32. Functions of the Inflammatory Response
Prevents spread of damaging agents
Disposes of cell debris and pathogens
Sets the stage for repair

33. Steps in the Inflammatory Response
Figure 12.8

34. Defensive Cells Natural killer cells Can lyse and kill cancer cells
Can destroy virus- infected cells

35. Antimicrobial Chemicals
Complement
A group of at least 20 plasma proteins
Activated when they bind to immune complexes or the foreign sugars found on bacterial cell walls (called complement fixation)
Figure 12.10

36. Antimicrobial Chemicals
Complement acts in a variety of ways:
Damage foreign cell surfaces
Vasodilators
Chemotaxis
Opsonization
Figure 12.10

37. Antimicrobial Chemicals
Interferon
Secreted proteins of virus-infected cells
Bind to healthy cell surfaces to inhibit viruses binding
Transferrins
Inhibit bacterial growth by reducing the amount of available iron

38. Fever Abnormally high body temperature
Hypothalmus heat regulation can be reset by pyrogens (secreted by white blood cells)
High temperatures inhibit the release of iron and zinc from liver and spleen needed by bacteria
Fever also increases the speed of tissue repair

39. Specific Defense: The Immune System – Third Line of Defense
Antigen specific – recognizes and acts against particular foreign substances
Systemic – not restricted to the initial infection site
Has memory – recognizes and mounts a stronger attack on previously encountered pathogens

40. Cells of the Immune System
Lymphocytes
Originate from hemocytoblasts in the red bone marrow
B lymphocytes become immunocompetent in the bone marrow
T lymphocytes become immunocompetent in the thymus
Macrophages
Arise from monocytes
Become widely distributed in lymphoid organs

41. Humoral (Antibody-Mediated) Immune Response
B cells with the proper receptors recognize and bind antigen particles (without having to be presented with them by an antigen-presenting cell)
The B cell is activated (and along with the stimulus from helper T cells) begins to form a clone
A large number of clones are produced (primary humoral response)

42. Humoral (Antibody Mediated) Immune Response
Most B cells become plasma cells
Produce antibodies to destroy antigens
Activity lasts for four or five days
Some B cells become long-lived memory cells (secondary humoral response)

43. Humoral Immune Response
Figure 12.12

44. Secondary Response Memory cells are long-lived
A second exposure causes a rapid response
The secondary response is stronger and longer lasting
Figure 12.13

45. Active Immunity Your B cells encounter antigens and produce antibodies
Active immunity can be naturally or artificially acquired
Figure 12.14

46. Passive Immunity Antibodies are obtained from someone else
Conferred naturally from a mother to her fetus
Conferred artificially from immune serum or gamma globulin
Immunological memory does not occur
Protection provided by “borrowed antibodies”

47. Genetic or innate (inborn) Acquired
Immunity
Genetic or innate (inborn)
Acquired
Naturally acquired
Active (getting the disease)
Passive (from mother)
Artificially acquired
Active: vaccine
Passive: immunoglobulins
A Kitson

48. Antibody Function
Antibodies are Y or T shaped soluble proteins. Each has two antigen binding sites particular to specific antigens. The remaining end is similar in all antibodies.
Antibodies inactivate antigens in a number of ways
Complement fixation
Neutralization
Agglutination
Precipitation

49. Antibody Function
Figure 12.16

50. Cellular (Cell-Mediated) Immune Response
a macrophage engulfs and digests a pathogen
the macrophage then pushes to its membrane surface the antigen from the digested pathogen (called antigen presentation)
a T cell that has receptor sites for that particular antigen then binds to the antigen on the macrophage’s surface and becomes activated (called T cell activation)
The activated T cell then clones resulting in a large number of T cells.

51. Cellular (Cell-Mediated) Immune Response
Figure 12.17

52. T Cell Clones Cytotoxic T cells Specialize in killing infected cells
Insert a toxic chemical (perforin)
Helper T cells
Recruit other cells to fight the invaders
Interact directly with B cells

53. T Cell Clones Regulatory T cells
Release chemicals to suppress the activity of T and B cells
Stop the immune response to prevent uncontrolled activity
A few members of each clone are Memory T cells

54. Summary of the Immune Response
Figure 12.19