Page 129 - Atlas of Histology with Functional Correlations

FIGURE 4.2 ■ Simple squamous epithelium: surface view of peritoneal

mesothelium. Stain: silver nitrate with hematoxylin. High magnification.

FIGURE 4.3 | Simple Squamous Epithelium:

Peritoneal Mesothelium Surrounding Small

Intestine (Transverse Section)

The simple squamous epithelium lining the pleural and peritoneal cavities is
called mesothelium. A transverse section of a wall of the small intestine

illustrates mesothelium (1), a thin layer of spindle-shaped cells with prominent
and oval nuclei. A thin basement membrane (2) is located directly under the
mesothelium (1). In a surface view, the disposition of these cells would appear
similar to those shown in Figure 4.2.

Mesothelium (1) and the underlying irregular connective tissue (5) form the

serosa of the peritoneal cavity. Serosa is attached to a layer of smooth muscle
fibers (6) called the muscularis externa serosa (see Fig. 4.1 parts 3 and 4). In
this illustration, the bundles of smooth muscle fibers (6) are cut in the transverse

plane. Also present in the connective tissue are small blood vessels (4), lined
also by a simple squamous epithelium called the endothelium (4), and numerous
fat (adipose) cells (3).

FIGURE 4.3 ■ Simple squamous epithelium: peritoneal mesothelium
surrounding the small intestine (transverse section). Stain: hematoxylin and
eosin. High magnification.

FUNCTIONAL CORRELATIONS 4.2 ■ Simple

Squamous Epithelium

In the peritoneal cavity, simple squamous epithelium reduces friction
between visceral organs by producing lubricating fluids and transports
fluid. In the cardiovascular system, this epithelium or endothelium allows

passive transport of fluids, nutrients, and metabolites across the thin

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