Somite ( primary segment , dorsal segment ; from ancient Greek σῶμα - “body”) - paired metameric formation in embryos , some invertebrates ( annelids , insects ) and all chordates (including humans ).
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Somites of Chordates
In the process of embryonic development, the middle germinal layer — the mesoderm — is divided into somites. Somites are located along the longitudinal axis of the body and adjacent to the sides of the neural tube and the notochord . In invertebrates, the entire mesoderm is segmented, in chordates, only its dorsal (dorsal) section; the rest of the mesoderm forms lateral plates - splanchnotomy .
Segmentation begins in the anterior part of the body and gradually spreads to the posterior part. In the process of development, each somite is differentiated into myotomy , sclerotome and dermatome , which are formed respectively: striated skeletal muscles , bones and cartilage of the skeleton (in fins also fins ) and the connective tissue part of the skin with its derivatives.
Sources
- Somit is an article from the Great Soviet Encyclopedia . .
- Somit - an article from the Dictionary of Medical Terms.