animal defences

• the skin - acts as a physical barrier, blocking pathogens from entering the body. also a chemical barrier by producing chemicals that are antimicrobial and can lower PH inhibiting growth of pathogens

  • skin cells secrete fatty acids such as oleic acid
  • skin cells secrete lysosome, enzyme that catalyses break down of carbs in cell walls of some bacteria
• mucous membranes - protect body openings. some membranes secrete mucus that traps pathogens and contains antimicrobial enzymes
• blood clotting - plugs wounds to prevent pathogen entry and blood loss.

  formed by a series of chemical reactions that occur when platelets are exposed to damaged blood vessels
• inflammation - triggered by tissue damage, damaged blood vessels release molecules which increases the permeability of the blood vessels so they leak fluid into the surrounding area. Causes swelling and helps to isolate an pathogens that entered.

  molecules also cause vasodilation which increases blood flow to the area making it hot and attracts White blood cells to fight the pathogens
• wound repair - surface of skin is repaired by outer layer of skin cells dividing and migrating to wound edges. tissue below contracts and brings edges together and is repaired by collagen fibres
• expulsive reflexes - expel foreign objects from the body e.g. coughing or sneezing