Simple columnar epithelium
and loose connective tissue form the surface
of the small intestinal mucosa.
The epithelial tissue layer of the small
intestine contains absorptive cells,
which take in nutrients, and goblet cells,
which secrete mucus. The epithelial surface forms many small projections,
called villi, one of which occupies most of this image.
The connective tissue layer of this or any mucosal
surface is called lamina propria.
Lamina propria is a loose connective tissue with a relatively high proportion
of cells. The defensive cells of the immune system are more numerous
here, close to a vulnerable surface, than in ordinary loose connective tissue
deeper in the body. Capillaries are usually abundant in lamina propria.
