File:Mesoderm cartoon 09.jpg

5. Somite Development - Loss of the Somite

Neural crest cells will migrate beside and through somite and finally the somite structure is lost and spreads as the 3 component parts.

1. Sclerotome - from the left and right somite at each level will engulf the notochord. This transient structure is then resegmented to form the axial skeleton, vertebra and intervertebral discs.
2. Dermatome - forms a thick band in the dorsal region of the embryo. This will then spread ventrally under the surface ectoderm (epidermis) to form the dermis of the skin.
3. Myotome - from the ventrolateral lip of the dermomyotome, spreads both dorsally and ventrally to eventually form skeletal muscle cells.
   1. Dorsally - the epimere which in turn forms epaxial muscles, located behind the vertebral column.
   2. Ventrally - the hypomere, which in turn forms hypaxial muscles, located on the ventral body wall and somites at the level of the limbs will also form limb muscles.

Note - the cartoons show just the embryo righthand side mesoderm development (the same events occur on the lefthand side).

Somite Links: 1 paraxial | 2 early somite | 3 sclerotome and dermomyotome | 4 dermatome and myotome | 5 somite spreading | SEM image - Human Embryo (week 4) showing somites | Movie - somitogenesis Hes expression

• Somite Cartoons
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  paraxial

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  early somite

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  sclerotome and dermomyotome

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  dermatome and myotome

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  somite spreading

Cite this page: Hill, M.A. (2024, April 25) Embryology Mesoderm cartoon 09.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Mesoderm_cartoon_09.jpg

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G