Lec 2- Epithelium

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University of Toronto Scarborough
Biological Sciences
Stefan Rusyniak

Lecture 2Epitheliumy Epithelium is difficult to define because of various fcns o Because of this have to be specialized o Secetionoff the surface of the epithelial cell and are designed for that role Ie wont be good at protection o Absorptiontaking things in tansporting through tissue Lining of gut specialized for that o Transportacross surface of epithelia Trachea moving of dust via mucus pushing it upo Sensory o Protectionbarrier protective lining Ex skin surface is E and it is specialized for dealing with adverse conditions Because thicker than most epithelia can remove layers of skin without damaging those underneath y EC o Why are they special o Arranged in sheets continuous layers linked together Not alot of gaps Covers the surface of something o Digestive tract cont with outside world lined by epithelium food comes from outside and anything inside that tube is from the ouside world still a barrier between u and outside world o Interior blood vessels also lined with epithelium o Free surface on slide because it was cut that way and will be covered by epitheliaCharacteristic feat of epithelium is that they have a free surfacePolaritydiff at bottom and top definitely a bottom and top and that they are diffaApexwill have diff stuff than the baseThese cells in sheetshave neighboring cellsEC sit on basement membraneLateral specializationsclose assoc with neighboring cells y Surface specializations o Microspecialized for absorption Majority of cells in intenstine have microvilli on the surface to absorb ingested food o Lumentube closed by epithelium inside is lumenFacing the lumen arte cells that have microvilli Can be arranged in tight arrangement when right next to each other Projection of the membrane withcytoskeleton mostly actinMeant to increase SA 203040 times Need that because want to increase RO absorption because more enzymes channels etc If u increase number of channels will absorb more things around the same timeMicrovilli brush border is when there are stacked really tightly together Microvili form brush border
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