Peritrophic membrane
Peritrophic membranes are non- cellular deposits of the midgut , which are formed in most of the arthropods . Usually, several peritrophic membranes form a common peritrophic shell that encloses the food within the intestine. This covering is permeable to nutrients and therefore allows them to be absorbed in the midgut. It can serve to protect the midgut, which as an endodermal organ does not form a solid cuticle , and thus prevent injuries from hard, pointed or sharp food components or the penetration of parasites . In addition, it can serve to compartmentalize the intestinal contents or play a role as a permeability barrier in the control of substance uptake.
Peritrophic membranes are formed either by the entire midgut epithelium, only the anterior section of the intestine, or by specialized cells at the beginning of the midgut, as in flies in the cardia . The peritrophic membranes consist of a basic substance consisting of proteins , glycoproteins and glycosaminoglycans and can therefore be regarded as a form of glycocalyx . Chitin-containing microfibrils are embedded in the basic substance in an irregular, hexagonal or orthogonal structure. Several morphologically and biochemically distinguishable membrane layers can be formed by an animal .
The peritrophic covering migrates with the food pulp through the intestine and is either destroyed again in the rectum or remains as a resistant covering around the faeces . In the case of aquatic animals, the latter results in a lowering of the compact excrement package and thus often a removal from the near-surface nutrient cycles.
literature
- Heinz Mehlhorn (Hrsg.): Outline of the zoology . 2nd Edition. Gustav Fischer Verlag, Stuttgart, Jena, New York 1995, ISBN 3-8252-1521-0 , pp. 174, 201 .
Individual evidence
- ↑ Entry "peritrophic membrane" in the compact lexicon of biology
- ↑ Volker Storch, Ulrich Welsch: Kükenthal zoological internship . 26th edition. Spektrum Akademischer Verlag, Heidelberg 2009, ISBN 978-3-8274-1998-9 , p. 247 .