Primary Defences Against Disease Flashcards
SKIN
main primary defence.
Acts as a physical barrier
Chemical barrier-releases chemicals that are anti-microbial and inhibit growth.
Outer layer is called the epidermis. It consists of layers of cells called keratinocytes.
Produced at the base of the epidermis by mitosis.
They migrate to the surface of the skin. As they migrate they dry out and the cytoplasm is replaced with the keratin: called keratinisation.
When cells reach surface they are no longer alive.
Keratinised layer of dead cells acts as effective barrier.
Blood clotting
Blood clothes plug wounds to prevent pathogen entry and blood loss. Forming a temporary seal.
Blotting clothing involves calcium ions and 12 other ‘clotting factors’ which are released by platelets.
Once a clot is formed it begins to dry out forming a scab. The scab shrinks as it drys, drawing the sides of the cut together while the skin underneath is repaired.
Skin repair
Deposition of fibrous collagen under scab.
Stem cells in the epidermis then divide and differentiate into keratinocytes and migrate the the edge of the cut.
New blood vessels grow to supply the new tissue with oxygen and nutrients.
The tissue contracts to pull the cut together to help complete repair.
When repair is complete the scab is released.
Mucous membrane ☀️
These protect body openings that are exposed to the environment such as nostrils and ears. As well as exchanges surfaces that are thinner and less well protected.
These are protected by mucous membrane. Mucous membrane consist of ciliated epithelium and goblet cells.
The goblet cells secrete mucus which lines passages and traps pathogens.
The cilia are long hair-like projections that move mucus up the trachea to the oesophagus and swallowed. Killed by acidity of stomach acid.
Inflammation 🔥🔥
Signs a tissue is infected is redness,swelling,heat and pain i.e. Inflammation.
The presence of micro organisms is detected by mast cells.
Mast cells release the cell signalling molecule histamine initiates a number of responses.
Vasodilation: makes capillary walls more permeable to white blood cells and proteins.
White blood cells help fight infection.
When wbc and proteins enter tissue fluid it causes swelling. The excess fluid is drained into lymphatic system where pathogens will come into contact with lymphocytes in order to initiate specific immune response.
Exclusive reflexes e.g coughing and sneezing.
Areas prone to attack are sensitive. They respond to irritation by sudden expulsions of air. In turn, the air carries with it the microorganisms causing the irritation.
