Somite

(redirected from Somites)
Also found in: Dictionary, Thesaurus, Medical.

somite

[′sō‚mīt]
(zoology)

Somite

 

a paired metameric formation in the embryos of such invertebrates as annelids and insects and in the embryos of man and all other chordates. The middle germ layer, or mesoderm, is segmented into somites during embryonic development. The somites are arranged along the longitudinal axis of the body alongside the neural tube and the chorda. The entire mesoderm is segmented in invertebrates, whereas in man and other chordates only its dorsal section is segmented, with the remaining mesoderm forming lateral plates, or splanchnotomes. Segmentation begins from the anterior section of the body and gradually extends to the posterior section. In the process of development, each somite decomposes into a myotome, a sclerotome, and a dermatome, from which are formed, respectively, the truncal musculature, the axial skeleton (in fish, also the skeleton of the fins), and the connective-tissue portion of the skin and its derivatives.

T. A. DETLAF

References in periodicals archive ?
bipunctatus has a long dactylus inserted disto-medially on ventral margin of propodus and overreaching the tip of this latter article, and a subtriangular telson, laterally expanded, which is wider than the sixth somite (Figs.
In addition, acupuncture injury at the 4th-5th somite from the cloaca was performed for in vivo observation of the dynamic macrophage and neutrophil migration process (Figure 3A and 3B).
This action suggests that sound production occurred by rubbing the narrow posterior edges of the somite exoskeleton against the anterior edges of the other somite exoskeleton.
Noggin acts downstream of Wnt and Sonic Hedgehog to antagonize BMP4 in avian somite patterning.
The abdomen of the larvae from the Atlantic coast of Mexico has dorsolateral processes on somite 5, which are absent in the Pacific population (Cuesta & Schubart 1999).
Results: Data showed that five aforementioned factors were co-expressed after 7 days in vitro by somites.
Treatment of C57BL/6J female pregnant mice with ethanol when the embryos have approximately 7-10 somites results in a pattern of malformation that is consistent with the DiGeorge sequence (midline clefts in the nose and cleft palate are features of this sequence.
Between d 11 and 17 the conceptus elongates to 25 cm, the primitive streak in the embryonic disc appears, and somites appear soon thereafter.
The Dmrt2 gene is expressed in gonadal tissues with species difference, as well as in some nongonadal tissues such as somites (Meng et al.
In brachyurans, the relative growth of the abdomen has been used only to estimate the size of females at puberty, because certain somites showed striking modification in growth and morphology during ontogeny (Huxley and Richards, 1931), whereas similar changes are not observed in males (Hartnoll, 1974).