Page 126 - Atlas of Histology with Functional Correlations

provide firm adhesion between cells, whereas the strong attachment sites of

desmosomes provide stability to cells subject to shearing stresses. At the base of
some epithelial cells, hemidesmosomes attach the cells to the basement
membrane, whereas the gap junctions allow for selective diffusion of molecules
between cells as well as rapid cell-to-cell communication.

TYPES OF EPITHELIA

Simple Epithelium

Simple squamous epithelium, called mesothelium, covers the external surfaces
of the digestive organs, lungs, and heart. Simple squamous epithelium, called
endothelium, lines the lumina of the heart chambers and all blood and lymphatic

vessels.

Simple cuboidal epithelium lines small excretory ducts in various organs.
In the proximal convoluted tubules of the kidney, the apical surfaces of the
simple cuboidal epithelium are lined with a brush border consisting of
microvilli.

Simple columnar epithelium lines the lumina of the digestive organs
(stomach, small and large intestines, and gallbladder). In the small intestine,
simple columnar absorptive cells that line the villi also exhibit microvilli, or a
brush border. Villi are finger-like structures that project into the lumen of the

small intestine. In uterine tubes and the uterine cavity of the reproductive tract,
the simple columnar epithelium also contains cells with motile cilia.

Pseudostratified Columnar Epithelium

Pseudostratified columnar epithelium lines the respiratory passages and
lumina of the epididymis and vas deferens. In the trachea, bronchi, and larger
bronchioles, some surface cells are lined with motile cilia; in the epididymis and
vas deferens, the surface cells exhibit long, nonmotile stereocilia.

Stratified Epithelium

Stratified squamous epithelium contains multiple cell layers. The basal cells

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