BIOLOGY 172 Lecture Notes - Lecture 32: Proximal Tubule, Collecting Duct System, Active Transport
Document Summary
Epithelial tissues cover the outside of body and line the organ surfaces; interface between organism and environment; layers of tightly packed cells. The (cid:862)outside of the (cid:271)od(cid:455) i(cid:374)(cid:272)ludes a(cid:374)(cid:455)thi(cid:374)g that does (cid:374)ot da(cid:373)age or (cid:272)ross (cid:272)ells(cid:863) (i(cid:374)(cid:272)ludes i(cid:374)side of the stomach, lungs, mouth, kidney) Apical membrane facer the outer environment; hostile environment. Basolateral membrane faces internal organs, connects to other tissues, Epithelial cells are sandwiched by tight junctions which prevent leakage between cells tightly zipped so no diffusion. All movement of molecules has to occur across apical membrane. Microvilli extend out of the apical membrane to create huge surface area to over small surface. Intestinal epithelial some tissues have a high surface to volume ration; to maximize area for transport of molecules across membrane; i. e. ) glucose. You want a higher surface area in lungs for oxygen exchange. Skin cells you want a lower surface area to stay tight for surface tension. Invaginations and folds increase surface area of epithelial tissues.
