communicable diseases, disease prevention and immune system Flashcards
whats a primary response
first line of defense to keep pathogens out of the body
how does skin keep pathogens out
keratinised cells - are dry and are constantly shed and replaced
normal flora - natural ecosystem of bacteria and fungi outcompete potential pathogens
sebum - acts as a natural antioxidant
how do mucous membranes keep pathogens out
goblet cells - secrete mucus to trap pathogens
cilia - waft mucus up and out of trachea to be digested
what are lysozymes and how do they keep pathogens out
enzymes found in urine and tears
they hydrolise macromolecules in pathogens
expulsive reflexes and how do they keep pathogens out
vomiting coughing sneezing etc
eject pathogen laden material away from body
blood clotting process
injured platelets and tissue release clotting factor prothrombin activator and calcium ions
prothrombin activator converts prothrombin –> thrombin
thrombin splits fibrinogen –> fribrin
fibrin forms a mesh over wound trapping platelets and rbc
enzyme plasmin is used to dissolve the clot
what is secondary defense
responses once pathogen is inside body
how does inflammation work
mast cells release cytokines and histamines
histamines signal cells of capillary endothelium to become more permeable
cytokines attract phagocytes
capillary widening –> increased blood flow
increased capillary permeability –> release of tissue fluid
what are phagocytes
specialised wbc that engulf and destroy pathogens
two types: neutrophils and macrophages
describe and explain function of the two types of phagocytes
neutrophils - multi-lobed, small, short lived, produced in large amounts in response to an infection,
contain lysosomes, engulf and digest pathogens and die shortly after, collected as pus
macrophages - larger than neutrophils, do not fully digest pathogens but display part of the pathogen on its membrane, becoming an antigen presenting cell
outline the process of phagocytosis
- pseudopods extend to surround pathogen
- pseudopods fuse to form a vesicle
- pathogen is engulfed forming a phagosome
- lysosome fuses w phagosome forming a phagolysosome
- hydrolisis of macromolecules in pathogen occurs
- simple molecules absorbed into cytoplasm, waste products removed via exocytosis
- antigens retained on cell surface membrane, becomes an antigen presenting cell alerting other cells of the attack
what are opsonins
chemicals that bind to pathogens and “tag” them so they can be recognised more easily by phagocytes for phagocytosis
what are antigens
usually polysaccharides/proteins, antigens trigger an immune response which involves production of antibodies
the specific immune response - B-cells
develop in bone marrow
- b-lymphocyte’s antibody binds with a complementary antigen
- clonal selection and proliferation- b-lymphocyte multiplies many times (clonal expansion)
- differentiation into memory cells or plasma cells which secrete large amounts of antibody
if antigen appears later the memory cells are stimulated , divide and produce many plasma cells quickly
the specific immune response - T-cells
develop in the thymus
- an antigen presenting cell (macrophage) ingests, processes and presents antigen
- T-helper lymphocyte or T-killer lymphocyte binds to complementary antigen on APC
- clonal selection and proliferation- one clone stimulated and T-lymphocyte divides many times
- differentiates into either T-killer or T-helper
T-killer - bind to cells presenting complementary antigen and kills them
T-helper - secrete cytokines which stimulate phagocytes and other lymphocytes
