Chapter 4
Tissue: The Living Fabric
123
4
(e)
Stratified squamous epithelium
Description:
Thick membrane composed of
several cell layers; basal cells are cuboidal or
columnar and metabolically active; surface
cells are flattened (squamous); in the
keratinized type, the surface cells are full of
keratin and dead; basal cells are active in
mitosis and produce the cells of the more
superficial layers.
Function:
Protects underlying tissues in
areas subjected to abrasion.
Location:
Nonkeratinized type forms the
moist linings of the esophagus, mouth, and
vagina; keratinized variety forms the
epidermis of the skin, a dry membrane.
Photomicrograph:
Stratified squamous epithelium
lining the esophagus (285
m
).
Stratified
squamous
epithelium
Nuclei
Basement
membrane
Connective
tissue
(f)
Transitional epithelium
Description:
Resembles both stratified
squamous and stratified cuboidal; basal cells
cuboidal or columnar; surface cells dome
shaped or squamouslike, depending on
degree of organ stretch.
Function:
Stretches readily, permits stored
urine to distend urinary organ.
Location:
Lines the ureters, bladder, and part
of the urethra.
Photomicrograph:
Transitional epithelium lining the bladder,
relaxed state (360
u
); note the bulbous, or rounded, appearance
of the cells at the surface; these cells flatten and elongate when
the bladder fills with urine.
Basement
membrane
Connective
tissue
Transitional
epithelium
Figure 4.3
(continued)
(e)
and
(f)
Stratiļ¬ed epithelium. (For related images, see
A Brief Atlas
of the Human Body
, Plates 7 and 10.)
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