Chapter 12, Lymphatic System

Chapter 12: Lymphatic System/Immunity
1. Lymphatic system
a. Two semi-independent parts
i. Lymphatic vessels
ii. Lymphoid tissues and organs
b. Lymphatic system functions
i. Transports escaped fluids back to the blood
ii. Plays essential roles in immunity
2. Lymphatic characteristics
a. Lymph—excess tissue fluid carried by lymphatic vessels
b. Properties of lymphatic vessels
i. One way system toward the heart
ii. No pump
iii. Lymph moves toward the heart
iv. Milking action of skeletal muscle
v. Rhythmic contractions of smooth muscles in vessel walls
3. Lymphatic vessels
a. Lymphatic capillaries
i. Walls overlap to form flap like mini-valves
ii. Fluid leaks into lymph capillaries
iii. Capillaries anchored to connective tissue by filaments
iv. Higher pressure on the inside closes mini-valves
v. Fluid forced along the vessels
b. Lymphatic collecting vessels (like veins)
i. Collect lymph from lymph capillaries
ii. Carry lymph to and away from lymph nodes
iii. Return fluid to circulatory veins near the heart:
1. Right lymphatic duct
2. Thoracic duct
4. Lymph: contains
a. Bacteria
b. Viruses
c. Cancer cells
d. Cell debris
5. Lymph nodes
a. Filter lymph before it is returned to the blood
b. Defense cells within lymph nodes:
c. Macrophages—engulf and destroy foreign substances
d. Lymphocytes—provide immune response to antigens
6. Other lymphoid organs
a. Spleen
b. Thymus—most active through early childhood
c. Tonsils
d. Peyer’s patches—attached in intestinal wall
7. Lines of defense
a. First line = skin and mucous membranes
i. Physical barrier to foreign materials
ii. Protective secretions
1. pH of skin is acidic to inhabit bacterial growth
2. sebum (oil) is toxic to bacteria
3. vaginal secretions are very acidic
b. Second line =
i. Phagocytes—cells that eat mostly bacteria
ii. Natural killer cells—contain toxic chemicals
iii. Fever—“cooks” invaders
iv. Inflammatory response—results in a chain of events leading to protection and healing
1. Redness
2. Heat
3. Swelling
4. Pain
c. Third line =
i. Immune response—immune system’s response to a threat
ii. Immunology—study of immunity
iii. Antibodies—proteins that protect from pathogens, attack antigen molecules
iv. Three aspects
1. Antigen specific—recognizes and acts against particular foreign substances
2. Systemic—not restricted to the initial infection site
3. Memory—recognizes and mounts a stronger attack on previously encountered pathogens
v. Types
1. Humoral immunity—antibody mediated immunity
a. Provided by antibodies present in body fluids
2. Cellular immunity—cell mediated immunity
a. Targets: virus-infected cells, cancer cells, and cells of foreign graphs