Lecture 16 Epithelial Transport and Glucose Uptake

Lecture 16 Epithelial Transport and Glucose Uptake - IPHY...

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Unformatted text preview: IPHY 3060 Lecture 17: Epithelial Transport and Glucose Uptake Epithelial cells form sheets lining body surfaces Epithelium lines the body • Blood vessels • Outside of body—skin • Respiratory tract • GI tract • Reproductive tract • Any other ducts, organs, tracts, etc. 2 Main Functions of Epithelial Layers: • To serve as a protective barrier • To selectively transport specific substances across this barrier Key Point #1: Epithelial cells are polarized—the two sides are not identical Epithelial Cells are Polarized • Apical side —faces into lumen • Basolateral side — faces away from lumen Lumen of vessel, duct, or tube Apical Side Basolateral Side Epithelial Layers, Cell-Cell Adhesions, and Protective Barriers Key Point #2: Cell-cell adhesions between epithelial cells help to form a tight protective barrier Cell-Cell Adhesions: Protein connections between cells 3 Types of Cell-Cell Adhesions in Epithelial Cells • Tight Junctions —“stitches” • Adherens Junctions — “patches” • Desmosomes —“rivets” Tight junction Adherens junction Desmosome Tight Junctions Transmembrane “stitches or zippers” that seal adjacent epithelial cells together Tight Junctions • Located just below the apical membrane • “Stitches or zippers” are transmembrane proteins on both cells that bind together to “sew or zip” membranes of adjacent cells together • Function is to restrict apical to basolateral diffusion between cells by stitching membranes of adjacent epithelial cells together Tight Junctions Tight Junction Proteins • Occludin • Claudins • JAMs Adherens Junctions • Found just below tight junctions • Consist of protein-protein “patches” sewn together to bind cells • Function is to bind cells to cells and serve as anchor sites for connection of actin cytoskeleton to cell membrane; do NOT restrict apical-basolateral diffusion Adherens junction Adherens Junctions Proteins • Cadherins —calcium-dependent transmembrane proteins • Catenins —bind cadherins to actin filaments Desmosomes • Found on basolateral membrane • Like “rivets” that link adjacent epithelial cells • Main functions are bind cells to cells and to matrix and to provide structural integrity to tissues by linking intermediate filament cytoskeletons of adjacent cells Desmosome Desmosome Proteins • Desmocollins and desmogleins —special cadherins • Plakoglobins and desmoplakins —link desmogleins and desmocollins to intermediate filaments Movement of Substances Across Epithelial Layers Cell-cell adhesions between epithelial cells...
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This note was uploaded on 08/11/2010 for the course IPHY 3060 taught by Professor Allen,davi during the Fall '09 term at Colorado.

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Lecture 16 Epithelial Transport and Glucose Uptake - IPHY...

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