Non-specific animal defences

What primary non specific defences are there

• Skin- barrier to entry of pathogens, has healthy microorganism which outcompete pathogens for space and oily sebum to inhibit pathogens

• Goblet cells- secrete mucus which traps pathogen

• Tears- contain lysosomes which destroy bacterial and fungal cell walls

• Serotonin- contracts smooth muscle in blood vessel walls

How does the process of blood clotting work

1. Damaged tissue exposed and platelets come into contact with collagen activating them

2. Thromboplast released and with Ca²⁺ catalyse conversion of prothrombin to thrombin

3. Thrombin catalyses conversion of fibrinogen into fibrin

4. Fibrin strands form mesh trapping RBC and platelets form clot which dries to scab

What inflammatory primary responses are there

• Histamines- dilate blood vessels heat kills pathogens and leak plasma to form TF which drains into lymph to kill pathogen by phagocytosis

• Cytokines- attract WBC= phagocytosis

What secondary defences are there

Phagocytosis where neutrophils (70%WBC) and macrophages engulf pathogens (4%)

How does phagocytosis work

1. Phagocyte attracted by pathogen chemicals and recognises it as non self and binds to it

2. Phagocyte engulfs pathogen to form phagosome and lysosome fuses to form phagolysosome, enzymes break pathogen down

3. Digested pathogen absorbed, antigens combine with MHC in cytoplasm

4. MHC/ antigen complex displayed on phagocyte membrane making an APC which stimulate specific immune response

MHC= major histocompaitibilty complex