12.5 Flashcards
What are non specific responses against pathogens?
- skin covers the body and prevents the entry of pathogens. It has a skin flora of healthy microorganisms that outcompete pathogens for space on the body surface. The skin also produces sebum an oily substance that inhibits the growth of pathogens
- Many of the body tracts including the airways of gas exchange system are lined by mucous membranes that secrete sticky mucus that traps microorganisms and contains lysozymes which destroy bacterial and fungal cell walls. Mucus also contains phagocytes which remove remaining pathogens
- Lysozymes in tears and urine and the acid in the stomach also help to prevent pathogens into our bodies
We also have expulsive reflexes, coughs and sneezes eject pathogen-laden mucus from the gas exchange system while vomiting and diarrhoea expel the contents along with infective pathogens
What happens when the blood clots and what role do platelets have?
- if you cut yourself, the skin is breached and pathogens can enter your body
- Blood clots rapidly seal the wound, when platelets come into contact with collagen in skin or the wall of the damaged blood vessel they begin to secrete substances
What is thromboplastin and serotonin?
- an enzyme that triggers a cascade of reactions resulting in the formation of a blood clot/thrombus
What is serotonin?
- Serotonin- makes the smooth muscle walls of the blood vessel contract so they narrow and reduce the supply of blood to the area
- Clot dries out forming a hard tough scab that keeps pathogens out- this is the first stage of wound repair
- Epidermal cells below the scab start to grow, sealing the wound permanently while damaged blood vessels regrow.
- Collagen fibres are deposited to give the new tissue strength
- Once the new epidermis has reached normal thickness, the scan sloughs off and the wound is healed
What is the inflammatory response?
- localised response to pathogens resulting in inflammation at the site of the wound
- So we characterised by pain, heat, redness and swelling of tissue
Mast cells are activated in the damaged tissue and release chemicals called HISTAMINES and CYTOKINES
What do histamines do?
- blood vessels dilate, causing localised heat and redness- this raised temp will kill pathogens and prevent them from reproducing
- Histamines make blood vessels (cytokines) are more leaky so blood plasma is forced out-becoming tissue fluid causing swelling and pain
What is the role of cytokines?
- attract white blood cells-phagocytes-to the site
- They dispose of pathogens by phagocytosis
What do cytokines do to the hypothalamus?
The cytokines stimulate the HYPOTHALAMUS to reset the thermostat and your temperature goes up.
This is a useful adaptation because, most pathogens reproduce above or below 37 degrees. Higher temperatures inhibit pathogen production and the specific immune system works better at higher temperatures.
What is phagocytosis?
- phagocytes are specialised wbc that engulf and destroy pathogens
- They consist of neutrophils and macrophages
- Phagocytes build up at the site of infection and attack pathogens, sometimes you can pus
- Pus consists of dead neutrophils and pathogens
What are the stages of phagocytosis?
- Pathogens produce chemicals that attract phagocytes
- Phagocytes recognise the non self antigens/proteins on the surface of the pathogen
- The phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
- Phagosome combines with lysosome to form a phagolysosome
- Enzymes from the lysosome digest and destroy the pathogen
Which WBC takes the longest to engulf a pathogen?
- neutrophils takes around 10 mins to fully engulf a pathogen
- macrophages have a more longer, time consuming process
