Mucosa of the small intestine

The small intestine needs a large absorption surface for the absorption of food components. The mucosal surface is greatly enlarged by means of strong folding and numerous protuberances. This is ensured by various structures:

Kerkig folds (Plicae circulares)These are annular folds that form the coarse relief of the small intestine and in which both the mucosa and submucosa protrude.
Small intestinal villi (Villi interstinales)In all sections of the small intestine there are these finger-shaped protuberances of 0.5-1.5 mm in size, in which the epithelium and the lamina propria are protuberant.
Lieberkühn-Krypten (Glandulae interstinales)In the valleys of the villi there are tubular depressions, which reach up to the lamina muscularis.
MicrovilliThis so-called “brush border” forms the micro relief of the small intestinal mucosa and enlarges it 10 times.
In the microvilli, the cytoplasm (filling content of the cells) of the individual small intestinal cells (enterocytes) is pushed out.

The histological differences of the individual small intestine sections are briefly described here:

Duodenum The duodenum is characterized by very high kerking wrinkles and by leaf-shaped impressing small intestinal villi. The most important feature, however, are the Brunner glands (Glandulae interstinales), which are only found in the duodenum. They are located in the submucosa and participate in the formation of the small intestine juice and produce enzymes such as maltase and amylase.
Empty intestine (jejunum) Here the kerking wrinkles become lower in the course of the day, the small intestine villi become longer and have a more finger-shaped structure
Crooked intestine (Ileum)The Kerking folds are particularly low in this small intestine-section and are missing in the lower ileum completely.
The villi of the small intestine also become shorter and shorter and the number of goblet cells increases in the course of the intestine. The numerous occurrence of lymph follicles (accumulation of lymph cells) in the ileum is particularly noticeable. If many follicles are gathered in one place, this place is also called Peyer’s plate. These structures are highly involved in the immune defence of the intestine.