| Type | MGI:General | Description | at E13, the bilateral cartilage centers of the atlas are smaller, the corpus atlantis is smaller, and the 2 halves of most cervical vertebrae have not yet made contact at E15, the arcus anterior atlantis and the dens epistrophei are absent and some vetebrae have still failed to fuse across the midline allowing the nuclei pulposi to form continuous dumbbell like structures at E16 development of the transverse processes of the sacral and upper caudal vertebrae is retarded at later stages the lateral parts of the arcus anterior of the atlas fail to form cartilage at birth, almost all centers of ossification are absent except occasionally in C6 and C7, most cervical vertebrae eventually fuse but retain visible signs of their bilateral origin, a rudimentary dens epistrophei is sometimes present, and vertebral transverse processes have not yet reached the differentiation stage seen in E16 controls embryos |
