diseases and immunity - key terms Flashcards
Define pathogen
a disease-causing organism.
Define transmissible disease
a disease in which the pathogen can be passed from one host to another.
Define direct contract
the pathogen is passed directly from one host to another through blood, body fluids, semen, etc.
Define indirect contract
the pathogen leaves the host and is carried in some way to another e.g., contaminated surfaces/food, from animals, from air
Define examples of mechanical barries
-Nostrils contain hairs that help trap dust
-The skin has a thick outer layer of dead cells
Define examples of chemical barriers
-Sticky mucus which can trap pathogens
-In the stomach, hydrochloric acid is secreted, which kills many of the bacteria in food
Define cells
Pathogens that manage to get through all these defences are destroyed by white blood cells.
Define antibody
proteins that bind to antigens, directly destroying or marking pathogens for destruction by phagocytes.
Define active immunity
defence against a pathogen by antibody production in the body.
Define passive immunity
short-term defences against a pathogen by antibodies acquired from another individual.
Define diarrhoea
loss of watery faeces
Define cholera/vibrio cholerae
Cholera is a disease caused by a bacterium transmitted in contaminated water.
The cholera bacterium produces a toxin that causes the secretion of chloride ions into the small intestine, causing lower osmotic water movement into the gut, causing diarrhoea, dehydration and loss of salts from the blood.