Page 600 - Atlas of Histology with Functional Correlations

Microvilli are tiny surface projections that appear as a pink-staining brush border

on absorptive cells in the intestine, especially when the slides are stained for
carbohydrates and examined with a light microscope. With a transmission
electron microscope, the brush border is seen as dense finger-like microvilli (1,
5) that project from the apical plasma membrane of absorptive cells. Although
microvilli (1, 5) are seen in different cell types, they are most prevalent lining the

villi of the small intestine.

The core of the microvilli (1, 5) consists of vertical actin microfilaments that
are attached to the cytoplasm by actin microfilaments called the terminal web
(2, 6). Also seen are numerous cytoplasmic vesicles (4), secretory granules (3),

and numerous mitochondria (7), sectioned in different planes.

FIGURE 15.9 ■ Ultrastructure of microvilli in an absorptive cell in the small

intestine. Courtesy of Dr. Rex A. Hess, Professor Emeritus, Comparative
Biosciences, College of Veterinary Medicine, University of Illinois, Urbana,
Illinois. ×6,150.

FUNCTIONAL CORRELATIONS 15.3 ■ Peyer

Patches in Ileum

The lamina propria and submucosa in the ileum contain numerous aggregates
of large lymphatic nodules called Peyer patches. Overlying these lymphatic
patches are specialized epithelial cells called the M cells whose cell

599