sets up adaptive immunity response (t cells, b cells, antibodies etc requires initiation by innate immunity) innate host defences against infections anatomical barriers/physical barriers. biological factors musical surfaces = sites of microbial encounters. Location eyes oral cavity all over body trachea/respiratory tract all inside body lungs stomach duodenum large intestine urogenital tract. S physical barrier; produces antimicrobial fatty acids; normal flora inhibits pathogen colonization. S lines the trachea suspend and move microorganisms out of the body. S desquamation high cell cycle turnover rate allows for high rates of skin sloughing mucous membranes. S peristalsis squeezing of intestine that moves food down, movement. Normal flora allows for high turnover rate. S in gi tract, cells only survive ~3 days, allows for high turnover rate. S cilia constantly move foreign agents to upper tract to be expelled. S flushing action of tears, saliva, mucous, urine. S opsonin enhances phagocytic uptakes by coating bacterial agents for easier identification.