human defence system

pathogen

is a disease - causing microorganism

types of pathogens

bacterium, fungus, virus

example of infection routes into body

contaminated food and drink, infected wounds, droplets breathed in

two types of defence systems in body

the general defence system and the specific defence system

general defence system

involves barriers and non-specific cell responses. it does not fight particular pathogens

description of skin

structural barrier

function of skin

prevents entry of pathogens

description of sweat

contains the enzyme lysozyme

function of sweat

kill pathogens

description of mutualistic bacteria

found of the skin and in the large intestine (colon)

function of mutualistic bacteria

stop harmful microorganisms growing

description of sebum

natural moisturiser (oil) produced by the sebaceous glands in skin

function of sebum

stops the skin cracking (opening)

description of acid

hydrochloric acid in stomach, lactic acid in vagina

function of acid

kills pathogens

description of mucus

in the breathing, digestive and reproductive system

function of mucus

traps pathogens

description of fever

high temperature

function of fever

denatures enzymes in the pathogen, destroying it

description of white blood cells

(called phagocytes/macrophages)

function of white blood cells

engulf pathogens by phagocytosis

description of platelets

clot blood when skin is cut

function of platelets

stops pathogens entering the body

description of histamine (blood)

chemical produced body cells

function of histamine (blood)

causes inflammation - blood vessels dilate so it is easier for white blood cells to get to the area of infection

description of interferon (blood)

chemical that body cells produce when they are infected by a virus

function of interferon (blood)

stops viral replication and so stop virus spreading

description of complement proteins (blood)

found in blood plasma

function of complement proteins (blood)

makes holes in the pathogens and burst them

the specific defence system

distinguishes between different pathogens and responds to each particular one