pathogens

• pathogen - a micro-organism that causes disease

• 4 main classes of pathogen - viruses, bacteria, fungi, protists

• semmelweis - noticed a difference in infection rates between two maternity wards.

• one maternity ward was staffed by midwives (clean), one was staffed by student doctors (dirty) who did autopsies

• this was used as proof that some sort of particle was responsible for disease

barriers to infection

• skin is a barrier

• the outer layer of skin cells is regularly shed (epidermis)

• this stops pathogens entering

• mucus membranes (not covered by skin cells)

• mucus traps pathogens

• in the trachea surface cells have cilia that beat to expel mucus and trapped pathogens

• blood clots

• is blood vessels are damaged a platelet plug bound with soluble fibrinogen will form which allows fibrin strands to bind the cells together to form an insoluble blood clot

innate imunity - recignition and destruction of pathogens

• some molecules are never found in the human body - therefore they are attacked by the body

• phagocytes are white blood cells that crawl (amoeboid movement) and engulf and digest pathogens

• the pathogen is taken into the cell through a vesicle which combines with a vesicle full of lysosomes which digest the pathogen.