Somite formation

Somite formation

1. By NABA’A AL WAZEN Molecular Regulation of Somite Formation and Differentiation

2. Somite A somite is a division of the body of an animal or embryo. Somites are bilaterally paired blocks of paraxial mesoderm that form along the head-to-tail axis of the developing embryo in segmented animals . In vertebrates, somites subdivide into the sclerotomes, myotomes and dermatomes that give rise to the vertebrae of the vertebral column, rib cage, and part of the occipital bone; skeletal muscle, cartilage, tendons, and skin

3. Development The mesodermis (one of the three primary germ layers in the very early embryo) forms at the same time as the other two germ layers, the ectoderm and endoderm. The mesoderm at either side of the neural tube is called paraxial mesoderm. The paraxial mesoderm is initially called the “segmental plate” in the chick embryo or the “unsegmented mesoderm” in other vertebrates

4. Formation The segmental plate commits to the somatic fate before mesoderm becomes capable of forming somite's. The cells within each somite are specified based on their location within the somite. Additionally, they retain the ability to become any kind of somite-derived structure. The development of the somites depends on a clock mechanism

5. 1 Somite 2 Somitocoel 3 Neural tube 4 Central canal of the neural tube 5 Coelom 6 Intermediary mesoderm 7 Splanchnopleura 8 Somatopleura

6. Differentiation of somite The tissue that immigrates via the primitive streak and initially forms the third germinal layer, the mesoderm, transforms itself several times . The epiblast-epithelial (ectoderm cells) are transformed into segmented mesoderm cells. In contrast to the epithelial cells, these are loosely organized. A new transformation follows, i.e., an epithelialization to become somites , which represent an epithelialized mesenchyma portion with a central somitocoel .

7. https:// en.wikipedia.org/wiki/Somite http:// www.embryology.ch/anglais/mmuskel/skelett02.html