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- organism or virus tt causes a disease
- e.g. viruses, bacteria, fungi, protozoa, flatworms
why aren't antibiotics effective on viruses?
- antibiotics block specific metabolic pathways o bac. cells leaving euk cells unharmed
- viruses invade host cells = eukaryotic, uses host cell's metabolic pathways to reprod
- antibiotics dont block processes euk cells
how does body recog. own tissues?
- major histocompatibility complex (MHC)
- MHC antigens protein molecules in phospholipid bilayer
- allows immune system to recog
- injury to lining blood vessels exposes connective tissue, platelets adhere (thrombocytes)
- platelet releases chemicals that make nearby platelets sticky
- release o clotting factors fr platelets, damaged cells, plasma } mix together and activate
- prothrombin precursor to thrombin enzyme activates
- soluble fibrinogen precursor to fibrin: fibrous protein
- platelet plug forms = emergency protection against blood loss
- reinforced by clot fibrin when vessel damage = more severe
- fibrin clot with trapped red blood cells
what are six steps of how phagocyte destroys microbes?
- some leukocytes are phagocytes, ingest pathogens in blood/body tissue
- phagosome forms
- fusion with lysosome
- detects microbes by chemicals they give off
- sticks microbes to its surface
- MHC antigens
microbe enguled by phagocyte wrapping pseudopodia around -> vesicle, endocytosis
phagosome (phagocytic vesicle) formed -> encloses microbe in membrane
fusion w/ lysosome
phagosome fuses with lysosome (contains powerful enzyme tt digests microbe)
microbes broken down by enzymes into their chemical constituents
indigestible material dischagrged fr phagocyte cell
- mature in Bone marrow
- two types: memory + plasma cells
- mature in thymus gland
- 3 types: helper T cell, cytotoxic T cell (killer t cell), suppressor T cell (calls off immune response)
- foreign molec. tt elicit specific response by lymphocytes
- e.g. antibody production
- such as surface molec. o viruses, bacteria, fungi, pollen, transplanted tissue
- antigen is a large molecule (protein, glycoprotein, lipoprotein or polysaccharide) on the outer surface of a cell.
- All living cells have these antigens as part of their cell membrane or cell wall.
- for cell-to-cell communication
- protein secreted by b cells (plasma cells) recognize + bind specific antigens
- destroy pathogen and antigen infections
- antibody (immunoglobulin) a protein molecule that can bind specifically to an antigen
two main types mechanisms used by body for defense?
- non-specific resistance: def. tt protect humans fr any pathogens
- specific resistance: targets specific pathogens carried out by lymphocytes + called immune response
skin and mucous membrane in def against pathogens
- ref two main types mechanisms for body defense
- skin: physical barrier, tough diff to penetratenature
- pop. harmless microbes inhibit growth pathogenic microbes
- sebaceous glands secrete chem-> lactic acid + fatty acids = skin acidic = prev bacterial growth
- tears + saliva help wash bacteria away
- mucous membranes: found in lining respiratory, urinary, reprod + gastrointestinal tracts
- mucous contains lysosome destroys many bac
- respiratory tract pathogens caught in sticky mucous + cilia then push mucus + bac up out o trachea -> swallowed/digested