Page 604 - Atlas of Histology with Functional Correlations

FIGURE 15.10 ■ Different cells and layers in the wall of the large intestine.

Supplemental micrographic images are available at

www.thePoint.com/Eroschenko13e under Digestive System Part III: Small
Intestine and Large Intestine.

Figure 15.11 | Large Intestine: Colon and

Mesentery (Panoramic View, Transverse Section)

The wall of the colon has the same basic layers as the small intestine. The
mucosa (4–7) consists of simple columnar epithelium (4), intestinal glands (5),

lamina propria (6), and muscularis mucosae (7). The submucosa (8) contains
connective tissue cells and fibers, various blood vessels, and nerves. Two smooth
muscle layers make up the muscularis externa (13). The serosa (visceral
peritoneum and mesentery) (3, 17) covers the transverse colon and the sigmoid

colon.

The colon does not have villi or plicae circulares, and the luminal surface of
the mucosa is smooth. In an undistended colon, the mucosa (4–7) and the
submucosa (8) exhibit temporary folds (12). In the lamina propria (6) and the
submucosa (8) are lymphatic nodules (9, 11).

The smooth muscle layers in the muscularis externa (13) of the colon are
different from those of the small intestine. The inner circular muscle layer (16)
is continuous and surrounds the colon wall, whereas the outer muscle layer is
condensed into three broad, longitudinal bands called taeniae coli (1, 10). A

very thin outer longitudinal muscle layer (15), which is often discontinuous, is
found between the taeniae coli (1, 10). The parasympathetic ganglion cells of the
myenteric (Auerbach) nerve plexus (2, 14) are found between the two smooth
muscle layers of the muscularis externa (13).

The transverse and sigmoid colon are attached to the body wall by a

mesentery (18). As a result, the serosa (3, 17) is the outermost layer.

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