Barriers to infection

Skin
1. Epidermis
  1. Mechanical barrier of dead epithelial cells
  2. Waterproof and frequently shed
2. Sweat galnds
  1. Sweat includes fatty acids to inhibit growth of some bacteria
3. Physical breach of the epidermis will lead to an inflammation response
GI tract
1. Low pH and thick mucus layer in the stomach
2. Mucus and immune surveillance in the small intestine
3. Proteases, lipases and bile released into the dueodenum
4. Competition by commensal micro-flora
5. Immune surveillance in the small intestine
  1. Crypt secretions
  2. Payers patches
6. Bile is released into the duodenum
  1. Produced by hepatocytes
  2. Alkaline bile neutralises stomach acid
  3. Bile salts act as bacteriocides
Stomach
1. Low pH and tick mucus layer in the stomach
Micro-flora
1. Produce antimicrobial agents to suppress pathogens
2. Important in defence and can influence development
Enzymes
1. Lysozyme breaks down peptidoglycan
Blood clotting
1. Coagulation system overlaps with the innate immune system
2. Increase vascular permeability
3. Act as chemotactic agents for phagocytic cells
4. Directly antimicrobial e.g. beta-lysine
5. 2 activation pathways
  1. Contact activation pathway (intrinsic pathway)
  2. Tissue factor pathway (extrinsic pathway)
6. There is inhibition of excessive clotting
Complement pathway

Resource summary

	Created by zambrella about 11 years ago