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Dana Philpott

LECTURE 02: Innate barriers to infection Epithelial cells first to encounter microorganism cells that line mucosal services Commensal flora newsworthy 5 different levels of protection beginning with innate barriers these services provide protective substances that protect from microbial infection If bypassed, cellular and humoral defences are first line of defense If the innate immune system fails rarely happens adaptive immunity system reacts including the antibodies, cytokines, etc. 7 services where microbes try to grain a foothold to infect Skin, internal organs are lined with epithelial cells that are in contact with external environment (food, air, etc.) urogenital tract v. expose to environment 8 in tears, enzymes called lysosomes can break holes in bacteria clear epithelial cells that line eyes tears contain substances that fight microbial infection Stomach very acidic few microorganisms can withstand the acidity Normal flora competes with different pathogens Commensal flora that live with humans defend against pathogens Anatomical barriers mechanical, chemical, biological Mechanical barriers prevent infection Squamous epithelial desquamates losing skin cells bacteria attached to skin cells will get sloughed off along with the skin cells Mucous membranes GI tract parastaliss squeezing push out bacteria with feces Respiratory epithelium ciliated cells cilia push bacteria particles back up into nose and mouth Epithelium flushes services away from bacterial infections Chemical factors Sweat has antimicrobial factors that can fight off infections Mucuous membranes low pH HCl produeced by parietal cells few can survive Lysozyme and phospholipase A poke holes in bacteria Defensins Surfactants in long opsonisation coat bacteria and make it easier to recognize by macrositic (?) cells, so easier to detect Biological factors normal flora antimicrobial substances competes for nutrients, so pathogens cannot gain a foothold on sufaces to infect
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