CH12 non-specific animal defences

Question 1

Skin adaptions to keep pathogens out

Answer 1

• covers body, preventing entry of pathogens
• has a skin flora of healthy microorganisms that outcompete pathogens for space on body surface
• skin produces sebum which inhibits growth of pathogens

Question 2

Body tract adaptations to keep pathogens out

Answer 2

• lined with mucous membranes that secrete sticky mucus
• traps microorganisms and contains lyzosomes which destroy bacterial and fungal cell walls

Question 3

Adaptations of urine and tears to keep pathogens out

Answer 3

• lyzosomes are present

Question 4

Blood clotting

Answer 4

• platelets come into contact with collagen in skin or wall of damaged blood vessel and adhere
• secrete thromboplastin (enzyme that triggers a cascade of reactions resulting in a blood clot) and serotonin (makes smooth muscle in walls of blood vessels to contract so they narrow and reduce blood flow to that area)
• clot dries out forming a hard, tough scab that keeps pathogens out
• epidermal cells grow below the scab and seal wound permanently while damaged vessels regrow
• collagen fibres deposited to give new tissue strength
• once new epidermis reaches normal thickness, scab sloughs off and wound is healed

Question 5

Inflammatory response

Answer 5

• results in inflammation at site of wound
• mast cells are activated in damaged tissues and release histamines and cytokines
• histamines make blood vessels dilate, causing localised heat and redness which raise temperature and prevent pathogens reproducing
• histamines make blood vessel walls more leaky so blood plasma is forced out, becomes tissue fluid which causes swelling and pain
• cytokines attract white blood cells to site

Question 6

Fevers

Answer 6

• normal body temperature is maintained by the hypothalamus in brain
• pathogen invades which stimulates hypothalamus to reset thermostat and temperature goes up
• higher temperatures inhibit pathogen reproduction
• specific immune system works better at higher temperatures

Question 7

Process of phagocytosis

Answer 7

• pathogens produce chemicals that attract phagocytes
• phagocytes recognise non-human proteins on pathogen
• phagocyte englufs pathogen and encloses in a vacuole called a phagosome
• phagocyte combines with a lysosome to form a phagolysosome
• enzymes from lysosome digest and destroy pathogens

Question 8

Macrophages

Answer 8

• once digested a pathogen, combines antigens from pathogen surface membrane with special glycoproteins in cytoplasm in MHC
• MHC complex moves these pathogen antigens to macrophages own surface membrane becoming an APC

Question 9

Opsonins

Answer 9

• chemicals that bind to pathogens and tag them so they can be located more easily
• phagocytes have receptors on their cell membrane that bind to opsonins and phagocyte then engulf pathogens