HUMB1000 Lecture Notes - Lecture 2: Stratified Squamous Epithelium, Epithelium, Free Surface
12 Jun 2018
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EPITHELIUM TISSUE
Epithelia form the surface layer f the body, line body cavities, hollow organs and structures,
and constitute most gland tissue. Any substance that enters or leaves the body must cross
an epithelium.
All epithelia consist of one or more layers of tightly
packed cells and little or no extracellular matrix between
cells. Distinguishing features of an epithelium include a
free apical surface and fixed basal surface.
Features of epithelia:
• free apical surface
• fixed basal surface
• specialized intercellular junctions
• basement membrane
Specialized intercellular junctions join adjacent cells, and a
thin basement membrane separates the basal surface
from underlying connective tissue layer. Although
epithelia lack blood vessels, many sensory nerve endings are present. Epithelia have a high
regenerative capacity that allows them to maintain their function.
Functions of epithelia
• resists dehydration and injury from physical, chemical, and biological agents
• regulate permeability
• secretion
• monitor environment though sensory input to nervous system
Epithelial tissues are classified using two basic criteria:
• the number of cell layers
❖ Epithelium composed of one layer →
simple
❖ two or more layers → stratified
• the shape of the cell at the apical surface
❖ thin and flat → squamous
❖ somewhat square shaped → cuboidal
❖ rectangular shaped → columnar
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Document Summary
Epithelia form the surface layer f the body, line body cavities, hollow organs and structures, and constitute most gland tissue. Any substance that enters or leaves the body must cross an epithelium. All epithelia consist of one or more layers of tightly packed cells and little or no extracellular matrix between cells. Distinguishing features of an epithelium include a free apical surface and fixed basal surface. Features of epithelia: free apical surface fixed basal surface: basement membrane specialized intercellular junctions. Specialized intercellular junctions join adjacent cells, and a thin basement membrane separates the basal surface from underlying connective tissue layer. Although epithelia lack blood vessels, many sensory nerve endings are present. Epithelia have a high regenerative capacity that allows them to maintain their function. Functions of epithelia resists dehydration and injury from physical, chemical, and biological agents regulate permeability: monitor environment though sensory input to nervous system secretion.
