Normal and Pathological Development of the Spine
The appearance of the vertebral column in the animal kingdom is of such great importance that the phylum Vertebrata, in which Homo sapiens is the most evolved species, is defined by the presence of this structure. At first simply represented by the notochord, the axial skeleton is associated with the vertebrae in the higher species, solidity thus being added to the flexibility of the primitive spine. The vertebrate animals are also characterized by the formation of a neural tube, developed on the posterior aspect of the notochord and enveloped by the vertebrae. Finally the phenomenon of metamerization, beginning in the higher invertebrates, represents a characteristic evolutionary trait of the vertebrates. The development of the spine is a perfect illustration of metamerization.
KeywordsVertebral Body Neural Tube Spina Bifida Ossification Center Posterior Arch
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