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The dermatome is the dorsal portion of the paraxial mesoderm somite which gives rise to the skin . In the human embryo, it arises in the third week of embryogenesis. [2] It is formed when a dermomyotome (the remaining part of the somite left when the sclerotome migrates), splits to form the dermatome and the myotome. [2]
For example, frogs have approximately 10, humans have 37, chicks have 50, mice have 65, and snakes have more than 300, up to about 500. Somite number is unaffected by changes in the size of the embryo through experimental procedure.
It is thought that early scleraxis-expressing progenitor cells lead to the eventual formation of tendon tissue and other muscle attachments. [1] Scleraxis is involved in mesoderm formation and is expressed in the syndetome (a collection of embryonic tissue that develops into tendon and blood vessels) of developing somites (primitive segments or compartments of embryos).
A dermatome is an area of skin that is mainly supplied by afferent nerve fibres from the dorsal root of any given spinal nerve. [ 1 ] [ 2 ] There are 8 cervical nerves (C1 being an exception with no dermatome), 12 thoracic nerves , 5 lumbar nerves and 5 sacral nerves .
Here, retinoic acid interacts with these pathways. [6] Early markers of somites exist but are not expressed in cephalic mesoderm, although the same cell types that are generated in somites are generated in cephalic mesoderm, such as angioblasts , myocytes , and a variety of connective tissues.
The lateral plate mesoderm is the mesoderm that is found at the periphery of the embryo.It is to the side of the paraxial mesoderm, and further to the axial mesoderm.The lateral plate mesoderm is separated from the paraxial mesoderm by a narrow region of intermediate mesoderm.
The somitomeres organize into somites which grow in pairs. In the fourth week, the somites lose their organization and cover the notochord and spinal cord to form the backbone. In the fifth week, there are 4 occipital somites, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 8 to 10 coccygeal that will form the axial skeleton.
Similarly a dermatome is an area of skin that a single nerve innervates with sensory fibers. Myotomes are separated by myosepta (singular: myoseptum ). [ 2 ] In vertebrate embryonic development , a myotome is the part of a somite that develops into muscle.