Defence Againts Pathogens Flashcards
list 6 primary, barriers that defined animals against infections by pathogens
skin
mucous membrane
Blood clotting
Inflammation
Wound repair
Exclusive reflexes
give two ways which skin helps defend animals against infection by pathogens:
acts as a physical barrier, blocking pathogens from entering the body
acts as a chemical barrier, produces chemicals that are antimicrobial and can lower pH, inhibiting the growth of pathogens.
function of mucous membranes
protect body openings and that are exposed to the environment (anus,mouth,nose,ears)
some membranes secrete mucus, a sticky substance that traps pathogens and contains antimicrobial enzymes
explain blood clotting and how it helps defend animals against infection by pathogens
a blood clot is a mesh of protein fibres,
blood clots plug wounds to prevent pathogens entry and blood loss,
they’re formed by chemical reactions that take place when platelets(cells in blood) are exposed to damaged blood vessels.
give ways which inflammation helps defend animals against infection by pathogens
- inflammation causes swelling, pain and redness,
can be caused by tissue damage,
damaged tissue releases a molecule which increases permeability of the bloody vessels, so they start to leak fluid around surrounding,
this causes swelling and helps to isolate any pathogens that may have entered the damaged tissue. - molecules also cause vasodilation(widening of the blood vessels) which increases blood flow to affected area, this makes area hot and brings white blood cells to the area to fight of any pathogens that may be present.
Explain wound repair and how it helps defend animals against infection by pathogens:
skin is able to repair itself after an injury and reform a barrier against pathogen entry,
surface is reformed by the outer layer of skin cells diving and migrating to the edges of the wound,
tissue below the wound then contracts to bring the edges of the wound closer, it is repaired using collagen fibres, scar can be caused due to too many collagen fibres.
provide 2 examples of expulsive reflexes and explain it
E.g. coughing and sneezing.
sneeze happens when the mucous membranes in the nostrils are irritated by things such as dirt and dust.
cough happens when there’s irritation in the respiratory tract.
Both coughing and sneezing are at attempt to expel foreign objects, including pathogens, from the body.
They happen automatically.
give three examples of how plants have physical defences against inflection by pathogens
waxy cuticle
cell walls
callose
explain how waxy cuticle defends against pathogens
plant leaves and stems have a waxy cuticle, which provides a physical barrier against pathogen entry.
may also stop water collecting on the leaf, which could reduce the risk of infection by pathogens that are transferred between plants in water
explain how the plant cell wall defends against pathogens
plants cells are surrounded by cell walls, these form a physical barrier against pathogens that make it past the waxy cuticle
explain how callose defends plants against pathogens
plants produced a polysaccharide called callose.
Callose gets deposited between plant cell walls and plasma membranes during times of stress such as pathogen invasion.
Callose deposition may make it harder for pathogens to enter cells.
Callose deposition at the plasmodesmata(small channels in the cell walls) may limit the spread of virus’s between cells.
give examples of plants chemical defences against pathogens
-produce antimicrobial chemicals which kill pathogens or inhibit their growth.
-produce chemicals called saponins, which destroy the cell meme ranges of fungi and other pathogens
-produce chemicals called phytoalexins, which inhibit the growth of fungi and other pathogens
-some chemicals secreted by plants and toxic to insects, it reduces the amount of insect feeding on plants and so reduces the risk of infection by plant viruses carried by insect vectors
