non-specific responses (animals)

• what is a parasite?

  An organism that lives or feeds in or on a host, causing it harm
• what is non-specific animal defences?

  response is immediate and the same for all pathogens
• what are specific animal defences?

  response is slower and specific to each pathogens
• list the 6 non-specific animal defences:

  skin

  mucus membranes

  blood clotting

  inflammation

  wound repair

  expulsive reflexes
• how does the skin defend against pathogens?

  acts as a physical barrier, blocking pathogens from entering. Also acts as a chemical barrier by producing chemicals that are antimicrobial and lower pH, inhibiting the growth of pathogens
• how do mucus membranes defend against pathogens?

  they protect the body openings that are exposed to the environment (e.g. mouth, nostrils, ears) Some membranes secrete mucus which traps pathogens and contains lysosomes to destroy pathogens
• how does blood clotting defend against pathogens?

  it's a mesh of protein (fibrin) fibres which plug wounds to prevent pathogen entry and blood loss. They're formed by a series of chemical reactions that take place when platelets are exposed to damaged blood vessels. The fibres trap platelets and form a clot.
• how does inflammation defend against pathogens?

  signs include: swelling, pain, heat and redness

  triggered by tissue damage --> damaged tissue releases molecules which increase the permeability of blood vessels so they start to leak fluid into the surrounding area. This causes swelling and helps to isolate any pathogens that may have entered the damaged tissue. The molecules also cause vasodilation (widening of the blood vessels), which increases blood flow to the affected area. This makes the area hot and brings white blood cells to the area to fight off any pathogens that may be present.
• how does wound repair defend against pathogens?

  the skin is able to repair itself after an injury and re-form a barrier. The surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound. The tissue below the wound then contracts to bring the edges of the wound closer together. It's repaired using collagen fibres - too many collagen fibres causes a scar.
• how do expulsive reflexes defend against pathogens?

  e.g. coughing and sneezing. A sneeze occurs when the mucus membranes in the nostrils are irritated by things such as dust or dirt. A cough is caused by irritation in the respiratory tract. Both coughing and sneezing are an attempt to expel foreign objects, including pathogens --> happens automatically