Page 591 - Atlas of Histology with Functional Correlations

ileum. Lymphatic nodules aggregate in the lamina propria and submucosa to

form the prominent Peyer patches.

Supplemental micrographic images are available at
www.thePoint.com/Eroschenko13e under Digestive System Part III: Small
Intestine and Large Intestine.

Figure 15.2 | Small Intestine: Duodenum

(Longitudinal Section)

The wall of the duodenum consists of four layers: the mucosa with the lining

epithelium (7a), the lamina propria (7b), and the muscularis mucosae (9, 12);
the underlying connective tissue submucosa with the mucous duodenal
(Brunner) glands (3, 13); the two smooth muscle layers of the muscularis
externa (14); and the visceral peritoneum serosa (15). These layers are

continuous with those of the stomach, small intestine, and large intestine (colon).

The small intestine is characterized by finger-like extensions, villi (7)
(singular, villus); a lining epithelium (7a) of columnar cells lined with the
microvilli that form the brush borders; light-staining goblet cells (2); and short,
tubular intestinal glands (crypts of Lieberkühn) (4, 8) in the lamina propria

(7b). Although the duodenal glands (3, 13) in the submucosa (13) characterize
the duodenum, such glands are absent from the rest of the small intestine
(jejunum and ileum) and the large intestine.

The villi (7) are mucosal surface modifications. Between the villi (7) are the

intervillous spaces (1). The lining epithelium (7a) covers each villus and the
intestinal glands (4, 8). Each villus (7) contains a core of lamina propria (7b),
strands of smooth muscle fibers (10) that extend upward into the villi from the
muscularis mucosae (9, 12), and a central lymphatic vessel called a lacteal (11)

(see Fig. 15.8 for details).

The intestinal glands (4, 8) are located in the lamina propria (7b) and open
into the intervillous spaces (1). In sections of the duodenum, the submucosal
duodenal glands (13) extend into the lamina propria (3). The lamina propria (7b)

also contains fine connective tissue fibers with reticular cells, diffuse lymphatic
tissue, and lymphatic nodules (5).

The submucosa (13) in the duodenum is almost completely filled with
branched, tubular duodenal glands (13). These glands (13) penetrate the

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