Jejunum, basic layers with plica (cross section)
The mucosa of the jejunum is typical of the small intestine, with villi and crypts.
In this specimen, a plica with its submucosal core is conspicuous across the center of the image.
Notice in this micrograph how the changing orientation of the mucosa with respect to the plane of section reveals the three-dimensional shape of villi and crypts.
In the upper half of the image (on "top" of the plica), the mucosa is cut in cross section so that villi appear as fingers and crypts appear as invaginations. This is the "standard" textbook view of intestinal mucosa.
In the lower half of the image ("below" the plica), the mucosa is cut tangentially so that villi appear as floating "islands" of tissue (with a core of lamina propria) while crypts appear as small "donuts" embedded within the mucosa (surrounded by lamina propria.
Muscularis externa of the jejunum has the standard inner circular and outer longitudinal layers of smooth muscle.
The serosa is to thin to appear on this low-magnification image, although its location is indicated.
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Last updated: 14 February 2002 / dgk