Midgut

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The midgut , also known as Mesodaeum or mesenteron , the middle portion of the intestine .

The midgut of the vertebrates

In the vertebrate embryo, the midgut is initially connected to the yolk sac over its entire length . It passes from the foregut at the anterior intestinal portal and into the hindgut at the posterior intestinal portal . With the curvature of the embryo, the midgut separates from the yolk sac and is incorporated into the embryo. Most of the definitive intestine arises from the midgut, from the end of the upper part of the duodenum ( pars superior duodeni ) to the Cannon-Boehm point in the area of ​​the large intestine .

The midgut of the invertebrate

In the molting animals (Ecdysozoa), the midgut is the part of the intestine that is formed endodermally and is therefore not skinned . Its shape is very variable in the different groups of animals and ranges from simple reed to highly differentiated formations. This suggests that it has arisen several times independently of one another in evolution. In some species, its front section is enlarged to a ventriculus , which is not homologous to the stomach of the vertebrates. At the beginning of the midgut, in some species in the middle or rear section, blind sacs ( caeca ) can be formed.

A midgut gland has formed independently of one another in various invertebrate taxa . This is about the portion of the intestine, which for the digestive important enzymes forms. Such a gland is found in molluscs , arachnids , crustaceans and starfish . In some representatives of these animal groups, the midgut gland also takes on the function of resorption and storage location for nutrients, in these cases one speaks of a hepatopancreas . Instead of a midgut gland, insects have an enzyme-producing midgut epithelium .

Individual evidence

  1. ↑ Michael Schünke: Prometheus - learning atlas of anatomy: internal organs . Georg Thieme, Stuttgart 2009, ISBN 978-3-13-139532-0 , p. 30-31 .
  2. ↑ a b K. Dettner, Werner Peters: Textbook of Entomology . 2nd Edition. Springer, Berlin 2011, ISBN 3-8274-1102-5 , pp. 97-110 .