Page 574 - Atlas of Histology with Functional Correlations

the pyloric gastric glands produce the enzyme lysozyme that destroys

bacteria in the stomach, and enteroendocrine gastrin-secreting cells (G
cells) secrete gastrin hormone, whose main function is to stimulate HCL
production by the parietal cells.

FIGURE 14.16 | Pyloric–Duodenal Junction

(Longitudinal Section)

The pylorus (1) of the stomach is separated from the duodenum (11) of the
small intestine by a thick smooth muscle layer called the pyloric sphincter (8)

formed by the thickened circular layer of the muscularis externa of the stomach
(9).

At the junction with the duodenum (11), the mucosal ridges (4) of the
stomach around gastric pits (3) become broader, irregular, and more variable in

shape. Coiled tubular pyloric (mucous) glands (6) in the lamina propria (5)
open at the bottom of the gastric pits (3). Lymphatic nodules (16) are seen
between the stomach (1) and the duodenum (11).

The mucus-secreting stomach epithelium (2) changes to the intestinal
epithelium (12) in the duodenum. The intestinal epithelium (12) consists of

goblet cells and columnar cells with apical brush borders (microvilli) that are
present throughout the length of the small intestine. The duodenum (11) contains
villi (13), a specialized form of surface modification. Between individual villi

are intervillous spaces (14) of the intestinal lumen.

Short, simple tubular intestinal glands (crypts of Lieberkühn) (15) are
present in the lamina propria of the duodenum. These glands consist of goblet
cells and cells with striated borders (microvilli) of the surface epithelium.

Duodenal glands (Brunner glands) (18) occupy most of the submucosa
(19) in the upper duodenum (11) and are the characteristic features of this part of

the duodenum. The ducts of the duodenal glands (18) penetrate the muscularis
mucosae (17) and enter the base of the intestinal glands (15), disrupting the
muscularis mucosae (17). Except for the esophageal (submucosal) glands proper,

the duodenal glands (18) are the only submucosal glands in the digestive tract. In
the muscularis externa of both the stomach (9) and the duodenum (20) are
neurons and axons of the myenteric nerve plexuses (10, 21).

573