Page 589 - Atlas of Histology with Functional Correlations

as regular and dense finger-like extensions of the absorptive cell cytoplasm. The

microvilli are coated by a glycoprotein coat (glycocalyx), which contains brush
border enzymes. The microvilli increase the absorptive luminal surface area
many fold.

Glands, Cells, and Lymphatic Cells and Nodules

in Small Intestine

Intestinal Glands

Located throughout the small intestine are the intestinal glands (crypts of
Lieberkühn). These glands open into the intestinal lumen at the base of the villi.
The simple columnar epithelium that lines the villi is continuous with that of the
intestinal glands that contain regenerative stem cells, absorptive cells, goblet

cells, Paneth cells, and enteroendocrine cells.

Intestinal Cells

Absorptive cells are the most common cells in the intestinal epithelium.

These cells are tall and columnar with a prominent brush border of
microvilli. A thick glycocalyx coat covers and protects the microvilli from
the corrosive digestive chemicals.
Goblet cells are interspersed among the columnar absorptive cells of the

epithelium. They increase in number toward the distal region of the small
intestine (ileum).
Enteroendocrine or diffuse neuroendocrine system (DNES) cells are
scattered throughout the epithelium of the villi and intestinal glands.

Duodenal (Brunner) glands are primarily found in the submucosa of the
initial portion of the duodenum and characterize this region of the small
intestine. These are branched, tubuloacinar glands with light-staining
mucous cells. The ducts of duodenal glands penetrate the muscularis

mucosae and discharge their secretory products at the base of intestinal
glands located between the villi.
Undifferentiated or stem cells are located at the base of intestinal glands,
and they exhibit increased mitotic activity. These stem cells replace all worn-

out columnar absorptive cells, goblet cells, and intestinal gland cells in the
small intestine.

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