EPITHELIAL TISSUES

SELECTED REFERENCES
1. Langman s Medical Embryology, 11th Edition by, TW
Sadler, ISBN: 978-1-6054-7656-8, pages-385,Publisher:
Lippincott.
2. Basic Histology, 12th Revised Edition, by Luiz
Junqueira, ISBN 9780071630207,

LECTURE OBJECTIVES
? define epithelia as sheets of contiguous cells, of varied embryonic
origin, that cover the external surface of the body and line internal
surfaces.
? explain the position, structure and function of the basement
membrane.
? describe the ways in which epithelia are classified, explaining what is
meant by the classification terminology, simple

Epithelia are cellular sheets that line the cavities of organs
and cover the body surface.
Epithelial tissues are composed of closely aggregated
polyhedral cells with strong adhesion to one another and
attached to a thin layer of extracellular matrix (ECM)

Based on cell shape simple epithelia are classified as squamous
(thin cell) , cuboidal (cell width and thickness ), columnar (cells
taller than they wide).

Cuboidal cells of epithelia generally have spherical nuclei. An extracellular basement
membrane (red) always lies at the interface of epithelial cells and connective tissue.
Nutrients for epithelial cells must diffuse across the basement membrane.
Basement membranes have many functions: They provide structural support and
polarity to epithelial cells and attach epithelia to underlying connective tissue.