Major fxn increase surface area at apical end of cell

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Unformatted text preview: ments in microvilli allow movements and connect with a “terminal web” (TW) of similar microfilaments in cell periphery. Major fxn: INCREASE SURFACE AREA AT APICAL END OF CELL, THUS INCREASING ABSORPTION! Epithelial cells that are specialized for rapid absorption at their apical ends usually have many microvilli, pinocytotic vesicles, many mitochondria, and long invaginations or folds of the basal membrane, with mitochondria aligned along these membrane folds. Fig. 4-29 Another apical specialization: Stereocilia – resemble long, branched microvilli and also are mainly to increase absorption by cells. Stereocilia are best seen on cells of the tall epithelial cells lining the epididymis. MOST CELLS HAVE MICROVILLI AND NOTTTT STEREOCILLIA. FOUND IN LINING OF EPIDIDMYS, WHERE SPERM ARE STORED TEMPORARILY. PROBS HAVE SAME FXN AS MICROVILLI -- TO PROMOTE ABSORPTIONS -- BUT THEYRE LONGER, MODIFIED MICROVILLI. Fig. 4-9 Apical specializations: Cilia – more robust and motile than stereocilia, for movement of cells or extracellular material. Common on epithelial cells lining respiratory system. With the TEM each cilium is seen to have 9 microtubule (MT) doublets surrounding 2 more MT...
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