Non-Specific Animal Defences
Keeping pathogens out:
Blood Clotting:
- Skin acts as a barrier to block the entry of pathogens.
- Sebum secreted by skin inhibits pathogen growth.
- Mucous membranes and mucous secreted by goblet cells trap pathogens.
- Lysosomes in tears and urine contain enzymes to kill pathogens.
- Acid in stomach denatures pathogens.
- Expulsive reflexes, such as sneezing, eject pathogens.
Blood Clotting:
- Open wounds are susceptible to infection, so the blood clots to keep pathogens out.
- The process of blood clotting is as follows.
Fever:
- Cytokines cause hypothalamus to increase body temperature, inhibiting pathogen production, and to provide the optimum temperature for the immune system.
- Inflammation is a localised response to pathogens which results in pain, swelling, redness and heat.
- Most damaged tissues release histamines and cytokines.
- Histamines make blood vessels dilate, causing an increase in temperature which stop the pathogen reproducing.
- Histamines cause blood vessels to become more permeable, so plasma is forced out producing swelling.
- Cytokines attract phagocytes, which destroy pathogens in phagocytosis.
- Phagocytes are cells which ingest and destroy pathogens, e.g. neutrophils and macrophils.
- The process of phagocytosis is the ingestion and destruction of pathogens, and is as follows: