Page 597 - Atlas of Histology with Functional Correlations

FIGURE 15.6 ■ Small intestine: jejunum with Paneth cells. Stain: Mallory-
Azan. ×40.

FUNCTIONAL CORRELATIONS 15.2 ■ Paneth

Cells and Enteroendocrine Cells in Small

Intestine

Paneth cells, located in the bases of intestinal glands perform defensive
functions in the digestive tract. Paneth cells produce lysozyme, an
antibacterial enzyme that digests the bacterial cell walls and membranes of
microorganisms. These cells also release the hydrophobic peptide defensin in

response to microbial presence. Thus, Paneth cells function in controlling the
microbial flora in the small intestine and regulating the microenvironment of
the intestinal crypts.

Enteroendocrine cells located in the epithelium of the small intestine
secrete numerous regulatory hormones for the digestive system, including

gastric inhibitory peptide, secretin, and cholecystokinin (pancreozymin). To
release these hormones into the capillaries, the secretory granules in these
cells are located in the base of the cells and are adjacent to the lamina propria

and the capillaries.

Gastric inhibitory peptide inhibits parietal cell production of
hydrochloric acid. Entrance of acidic chyme into the duodenum also causes a
release of the hormone secretin, which influences the exocrine cells of the
pancreas to secrete a bicarbonate-rich fluid that neutralizes the luminal

acidity and promotes the action of digestive enzymes in the small intestine.

596