Page 142 - Atlas of Histology with Functional Correlations
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SECTION 1 Classification of Epithelial Tissue
EPITHELIAL TISSUE
Major Features
Classification is based on number of cell layers and cell morphology
Basement membrane separates epithelium from connective tissue
Almost all epithelia are nonvascular, except the epithelium in the inner ear,
which is vascular
Delivery of nutrients to epithelial cells and removal of metabolic waste occur
via diffusion from adjacent capillaries
Surface modifications include motile cilia, microvilli, and nonmotile
stereocilia
Lateral cell surface modification includes zonulae occludentes, zonulae
adherens, desmosomes, gap junctions, and hemidesmosomes basally
Types of Epithelia
Simple Squamous Epithelium
Single layer of flat or squamous cells; includes mesothelium and endothelium
Mesothelium lines external surfaces of digestive organs, lung, and heart
Endothelium lines inside of heart chambers, blood vessels, and lymphatic
vessels
Functions in filtration, diffusion, transport, secretion, and reduction of
friction
Simple Cuboidal Epithelium
Single layer of round cells
Lines small ducts and kidney tubules
Protects ducts; transports and absorbs filtered material in kidney tubules
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