Each vertebra is made of a large anterior portion called the body, and the posterior part called the vertebral arch.

每块椎两部分组成：前面宽大部分叫做椎体，后面突出部分叫做椎弓。

This constitutes a defect or absence of the vertebral arches, due to failure of mesoderm to organize over the region of the defect, and it may or may not involve the underlying meninges and neural tissue.

这导致了椎弓畸形或缺失，这中胚层不能在缺陷区域处生长；椎弓缺失可能影响其下脑脊膜和神经组织。