ch. 12 | the lymphatic system & immunity

• functions:

1. drainage- interstitial fluid is carried through the system & empties into the veins, where it becomes part of the blood plasma again
2. transport- moves lipids & lipid-soluble vitamins from digestive tract to blood 
3. immunity- lymphocytes fight foreign cells 

• lymph: when interstitial fluid enters lymphatic vessels; drained by lymphatic or thoracic duct 

• primary lymphatic organs: (sites where stem cells divide & develop into B & T cells)

-red bone marrow

-thymus

• T-cells= T lymphocytes (made in red bone marrow & matures in thymus)
• B-cells = B lymphocytes (made & mature in red bone marrow)

• secondary lymphatic organs: (sites where most immune responses occur)

-spleen: largest lymphatic organ

• pathogens: disease-causing organisms

immunity: ability to protect against disease 

• innate immunity: series of non-specific physical & chemical defenses 

-physical barriers: skin, mucous membranes in the nose, upper respiratory tract, intestines, reproductive & urinary systems

-chemical barriers: chemicals w/in various fluids & secretions, killer cells, inflammation, & fever can slow growth of microbes

• adaptive immunity: ability to adapt to specific types of infections or antigens
• cell-mediated immunity: effective against INTRAcellular pathogens, involves T-cells, always involves cells attacking cells 
• antibody-mediated immunity: effective against EXTRAcellular pathogens, involves B-cells

-cell-mediated & antibody-mediated immunity often work together to rid the body of antigens

• active immunity: exposed to antigens & body develops antibodies in response; stays for longer periods bc memory cells
• passive immunity: received pre-made antibodies that body can use to defend itself; fleeting
• autoimmunity: immunological response against a person's own tissues (immune cells attack your own body cells)

immune response time speeds up after the initial exposure 

-initial response to infection may take several days or weeks

-clonal selection process produces memory cells 

-subsequent exposure to the same antigens--> secondary immune response which is stronger

• vaccination: receipt of a vaccine (consists of weakened pathogens)

• acquired immunodeficiency syndrome (AIDS): condition in which a person experiences many infections due to progressive destruction of cells of lymphatic system
• human immunodeficiency virus (HIV): virus that causes AIDS

-it is not easy to get infected w it 

-cannot be exchanged through casual contact- usually through exchange of body fluids

-symptoms progress SLOWLY & progress in severity 

-is a retrovirus (a virus that can convert its RNA into DNA)