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In vertebrates, somites subdivide into the dermatomes, myotomes, sclerotomes and syndetomes that give rise to the vertebrae of the vertebral column, rib cage, part of the occipital bone, skeletal muscle, cartilage, tendons, and skin (of the back). [2] The word somite is sometimes also used in place of the word metamere.
Somitogenesis is the process by which somites form. Somites are bilaterally paired blocks of paraxial mesoderm that form along the anterior-posterior axis of the developing embryo in vertebrates. The somites give rise to skeletal muscle, cartilage, tendons, endothelium, and dermis [1].
The somites give rise to the vertebral column , associated muscles , and overlying dermis . There are a total of 37 somite pairs at the end of the fifth week of development, after the first occipital somite and 5-7 coccygeal somites disappear from the original 42-44 somites.
Somitogenesis is the process by which somites, blocks of mesoderm that give rise to a variety of connective tissues, are formed. The model describes the splitting off of somites from the paraxial mesoderm as the result of oscillating expression of particular proteins and their gradients.
As the primitive streak continues to regress, somites form from the paraxial mesoderm by "budding off" rostrally. In certain model systems, it has been shown that the daughter cells of stem cell-like progenitor cells which come from the primitive streak or site of gastrulation migrate out and localize in the posterior paraxial mesoderm.
The face and neck development of the human embryo refers to the development of the structures from the third to eighth week that give rise to the future head and neck.They consist of three layers, the ectoderm, mesoderm and endoderm, which form the mesenchyme (derived form the lateral plate mesoderm and paraxial mesoderm), neural crest and neural placodes (from the ectoderm). [1]
In 1832, Jonathan the Seychelles giant tortoise (Aldabrachelys gigantea hololissa) was born. Although his exact birthdate is unknown, he has been given the official birthday of December 4, 1832.
The cells that migrate through the most cranial part of the primitive line form the paraxial mesoderm, which will give rise to the somitomeres that in the process of somitogenesis will differentiate into somites that will form the sclerotomes, the syndetomes, [18] the myotomes and the dermatomes to form cartilage and bone, tendons, dermis (skin ...