1. The Lymphatic System and Body Defenses

2. The Lymphatic System Consists of two semi-independent parts
Lymphatic vessels
Lymphoid tissues and organs
Lymphatic system functions
Transport fluids back to the blood
Body defense and resistance to disease

3. 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

4. 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

5. Lymphatic Vessels

6. 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 at the right lymphatic duct or thoracic duct

7. Lymph Lymph returned to the blood is composed of: Water Blood cells
Proteins
Harmful materials that enter lymph vessels
Bacteria
Viruses
Cancer cells
Cell debris

8. Lymph Nodes Filter lymph before returning to the blood
Contain defense cells:
Macrophages – engulf and destroy foreign substances
Lymphocytes – provide immune response to antigens

9. Lymph Nodes

10. Lymph Node Structure Most are kidney-shaped, <1 inch long
Cortex - outer part
Contains follicles with lymphocytes
Medulla - Inner part
Contains phagocytic macrophages

11. The 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

12. Other Lymphoid Organs
Several other organs contribute to lymphatic function:
Spleen
Thymus
Tonsils
Peyer’s patches

13. The Spleen Located on the left side of the abdomen
Filters blood – cleanses blood of bacteria, viruses and debris
Destroys worn out blood cells
Stores platelets
Acts as a blood reservoir
Forms blood cells in the fetus (hematopoietic)
Produces lymphocytes only in the adut spleen

14. The Thymus Located low in the throat, overlying the heart
Functions at peak levels only during childhood
Produces hormones (like thymosin) to program lymphocytes

15. Tonsils Small masses of lymphoid tissue around the pharynx
Traps and removes bacteria and other foreign materials
Tonsillitis = is caused by congestion with bacteria

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

17. 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 from foreign matter

18. Body Defenses
The body is constantly in contact with bacteria, fungi, and viruses
The body has two defense systems for foreign materials
Nonspecific defense system
Specific defense system

19. Body Defenses Nonspecific defense system Specific defense system
Mechanisms protect against a variety of invaders
Responds immediately to protect body from foreign materials
Provided by body surface coverings
intact skin, mucous membrane, cellular proteins and inflammatory response.
Specialized human cells
Chemicals produced by the body
Specific defense system
Known as the immune system
Specific defense is required for each type of invader

20. Body Defenses
Figure 12.6

21. Surface Membrane Barriers 1st 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

22. Defensive Cells Phagocytes (neutrophils and macrophages)
Engulfs foreign material into a vacuole
Enzymes from lysosomes digest the material
Natural killer cells
Can lyse and kill cancer cells
Can destroy virus- infected cells
Figure 12.7a

23. Events of Phagocytosis

24. Inflammatory Response – 2nd 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
Inflammatory Response

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

26. The Inflammatory Response
Begins with a chemical ‘alarm”- Histamines when cells are injured
Blood vessels dilate increases blood flow to area causing redness and heat.
Capillary beds become permeable becoming leaky, which increases edema
Pain receptors are activated
Phagocytes and WBC are attracted to the area:
Chemotaxis = cells follow chemical gradient

27. Antimicrobial Chemicals
Complement proteins
20 active plasma proteins circulating in the blood
Attach to foreign cells and fight against them.
Interferon
Secreted proteins of virus-infected cells
Bind to healthy cell surfaces to inhibit viruses binding

28. Fever Abnormally high body temperature
Systemic response to invading microorganisms
Heat regulated by Hypothalmus ‘thermostate’ - reset upwards 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

29. Specific Defense: The Immune System 3rd Line of Defense
Antigen specific – recognizes and acts against particular foreign substances
It stalks and eliminates any invading pathogen
Systemic – not restricted to the initial infection site
Has memory – recognizes and mounts a stronger attack on previously encountered pathogens

30. 2 Types of Immunity Humoral immunity Cellular immunity
Its Antibody-mediated immunity where antibodies are present in the body’s fluids
Cells produce chemicals for defense
Cellular immunity
Cell-mediated immunity where lymphocytes themselves defend the body.
Cells are the protective factors that target virus infected cells

31. Antigens (Nonself = foreign intruders)
Antigen = any substance capable of exciting the immune system and provoking an immune response
Examples of common antigens:
foreign proteins, nucleic acids, large carbohydrates, pollen grains, microorganisms
As the immunity system develops, it inventories all these proteins so it recognizes them as self.

32. 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

33. Allergies
Many small molecules (called haptens or incomplete antigens) are not antigenic, but link up with our own proteins
The immune system may recognize and respond to a protein-hapten combination
The immune response is harmful rather than protective because it attacks our own cells
Haptens are found in chemicals, poison ivy, animal dander, detergens, hair dyes, cosmetics, housefold/industrial products.

34. Crucial Cells of the Immune System
2 types of Lymphocytes
B lymphocytes (B cells) become immunocompetent in the bone marrow; produce antibodies, oversee humoral immunity.
T lymphocytes (T cells) become immunocompetent in the thymus;
Originate from hemocytoblasts in the red bone marrow
Macrophages
Arise from monocytes
Become widely distributed in lymphoid organs
Do not respond to specific antigens but help lymphocytes do that

35. Activation of Lymphocytes

36. 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

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

38. Passive Immunity Antibodies are obtained from someone else
From a mother to her fetus
Artificially from immune serum or gamma globulin
Immunological memory does not occur
Protection provided by “borrowed antibodies” is short-lived

39. Monoclonal Antibodies
Antibodies prepared for clinical testing or diagnostic services
Produced from descendents of a single cell line and exhibit specificity for only one antigen.
Examples of uses for monoclonal antibodies
Diagnosis of pregnancy
Treatment after exposure to hepatitis and rabies

40. Antibodies (Immunoglobulins) (Igs)
Soluble proteins secreted by B cells (plasma cells)
Carried in blood plasma
Capable of binding specifically to an antigen
Figure 12.15a

41. Antibody Structure Four amino acid chains linked by disulfide bonds
Two identical amino acid chains are linked to form a heavy chain
The other two identical chains are light chains
Specific antigen-binding sites are present
Figure 12.15b

42. Antibody Classes
Antibodies of each class have slightly different roles
Five major immunoglobulin classes
IgM – can fix complement
IgA – found mainly in mucus
IgD – important in activation of B cell
IgG – can cross the placental barrier
IgE – involved in allergies

43. 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
Suppressor 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 cells

44. Organ Transplants and Rejection
Major types of grafts
Autografts – tissue transplanted from one site to another on the same person
Isografts – tissue grafts from an identical person (identical twin)
Allografts – tissue taken from an unrelated person
Xenografts – tissue taken from a different animal species (Bovine)

45. Organ Transplants and Rejection
Autografts and isografts are ideal donors
Xenografts are never successful
Allografts are more successful with a closer tissue match

46. Disorders of the Immunity
Allergies (Hypersensitivity)
Immunodeficiencies
Autoimmune Diseases

47. Disorders of Immunity: Allergies (Hypersensitivity)
Abnormal, vigorous immune responses
(2) Types of allergies:
1)- Immediate hypersensitivity
Triggered by release of histamine from IgE binding to mast cells
Reactions begin within seconds of contact with allergen
Anaphylactic shock – dangerous, systemic response

48. Disorders of Immunity: Allergies (Hypersensitivity)
2) Delayed hypersensitivity
Triggered by release of lymphokines from activated helper T cells
Symptoms usually appear 1–3 days after contact with antigen
Example: Contact dermititis

49. Disorders of Immunity: Immunodeficiencies
Production or function of immune cells or complement is abnormal
May be congenital or acquired
Includes AIDS – Acquired Immune Deficiency Syndrome SCID – Severe combined immunodeficiency disease (bubble babies)

50. Autoimmune Diseases
The immune system does not distinguish between self and nonself
The body produces antibodies and sensitized T lymphocytes that attack its own tissues
Multiple sclerosis – myelin sheath of brain & spinal cord are destroyed
Myasthenia gravis – impairs communication between nerves & skeletal muscles
Glomerulonephritis – impairment of renal function
Type I diabetes – destroys pancreatic beta cells that produce insulin
Rheumatoid arthritis – destroys joints
Systemic lupus erythematosus – affects kidney, heart, lung & skin

51. Developmental Aspects of the Lymphatic System
Lymphoid organs are poorly developed before birth, except the thymus & spleen
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