Segmentation (biology)

The segmentation of many organisms, that is, the subdivision of the body in primary identical (homologous and analogous ) sections is a result of pattern formation in the embryonic stage (→ morphogenesis ). Segmentation is striking especially in worms (eg earthworm ) and arthropods (eg millipedes ).

Mostly, segmentation may be observed during early ontogeny, after which the body segments often merge.

With the emergence of worms belt of the segmentation is reduced to a kind of " budding ": Early subdivisions of the flatworm embryos give rise Teloblastzellen, which are stem cells that divide asymmetrically.

In insects, the segmentation is particularly pronounced in the early larval stages. Also, all vertebrates are basically constructed segmentally (eg somites, vertebrae or ribs with intervening nerves and blood vessels). The zebrafish is the preferred object for the study of segmentation in vertebrates.

In many groups of animals, such as arthropods, individual segments are fused to the body portions, the tagmata. Secondary to the individual segments in the course of phylogeny function differentiation know ( homology but no analogy ).

The individual segments are called metamers. However, metamerism is not entirely synonymous with segmentation, but it is a distinction between coelomatischer metamerism ( coelom divided ), homonomer metamerism (segments equal multiform ) and heteronomous metamerism (segments designed differently ).

Segmentation in plants are found primarily at lower and higher algae.

Single Documents

• Embryology
• Morphology
• Anatomy (eddy lots)