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Unformatted text preview: immune system a set of mechanisms to protect an organism against pathogens: viruses, bacteria, single-cell eukaryotic parasites (yeast,) parsitic worms, maggots lymphoid tissues thymus, bone marrow, lymph nodes, spleen. essential parts of the defense system blood (closed circulataory system): suspends red and white blood cells and platelets lymph consists of fluids that accumulate outside of the closed circulatory system in the lymphatic system lymphatic system a branching system of tiny capillaries connecting larger vessels. these lymph ducts connect to larger vessels that eventually lead to a large vein near the heart. along the lymph vessels are small, roundish lymph nodes. lymph nodes contain a variety of white blood cells. stem cells cells where all blood cells originate. located in the bone marrow. leukocytes white blood cells red blood cells *found in the closed circulatory system only. *smaller than white blood cells *lose their nuclei before they become functional *cannot leave the circulatory system *transport oxygen and carbon dioxide *smooth white blood cells *found in circulatory system and lymphatic system *can leave the circulatory system *larger than red blood cells *clear colored and have a nucleus and organelles *the number of white blood cells can rise in response to invading pathogens *two types: phagocytes and lymphocytes *look like they're covered in coconut phagocytes a type of white blood cell that engulf and digest foreign materials. types include neutrophils, monocytes and macrophages, eosinophils, and dendritic cells. the process of ingesting pathogens is called "phagocytosis" several types of phagocytes: neutrophils, monocytes which mature into macrophages, eosinophils, and dendric cells lymphocytes most abundant. type of white blood cells. two types: B and T cells T cells a type of lymphcyte that migrates from the circulation to the thymus, where they mature B cells circulate and also collect in lymph vessels. make antibodies. platelets cell fragments without nuclei. initiate blood clotting. smaller than red and white blood cells. Nonspecific defenses Done by the innate immune system. Various mechanisms: Skin is a barrier Bacteria and fungi on the surface of the body (normal flora) compete for space and nutrients against pathogens Tears, nasal mucus, and saliva contain the enzyme lysozyme that attacks the cell walls of many bacteria. Mucus and cilia in the respiratory system trap pathogens and remove them. Ingested pathogens can be destroyed by the hydrochloric acid and proteases in the stomach. In the small intestine, bile salts kill some pathogens. neutrophils phagocytes. most abundant type of white blood cells (70%). neutrophils can only execute one phagocytic event, expending all of their glucose reserves in an extremely vigorous "respiratory burst" they attack pathogens in infected tissue they react fast (within an hour of an insult) the average halflife of a non-activated neutrophil in the circulation is about 4-10 hours...
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This note was uploaded on 04/09/2008 for the course MCDB 1B taught by Professor Weimbs during the Spring '08 term at UCSB.
- Spring '08