Axial Skeleton: Embryonic Origins

The axial skeleton arises from the scleratomal portion of the somite, of paraxial mesoderm. [A]

 A. Traditionally, it is thought that the sclerotomes divide into cranial and caudal halves.
B. These halves then join with the adjacent half of the next scleratome (remember that the somitic mesoderm is segmental!) and the costal process forms on the posterior segment, where the rib will later attach.
C. This junction forms the centrum of each vertebrae, which will surround the notochord and form a bony floor for the spinal cord. The more lateral scleratomal cells give rise to the neural arches, which fuse with each other and with the centrum to form the dorsal roof of the spinal cord.

 

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