Department of Neuroradiology, Hospital for Sick Children, University of Toronto, Toronto, ON, M5G1X8, Canada.
Neurol Sci. 2011 Dec;32 Suppl 3:S267-70. doi: 10.1007/s10072-011-0693-2.
The occipital bone is the upper end of the somatic spine, limited cranially by the tentorium. The bony craniovertebral junction (caudal occiput, atlas, and axis) is interposed between the unsegmented occipital and the intersegmental spinal sclerotomes, separated from the occiput and C3 by the intrasegmental clefts of O4 and C2 sclerotomes, respectively. It retains a primitive segmental hypocentrum (anterior arch of C1) and is unsegmented from caudal O4 to cranial C2 half-sclerotomes (axis). Its morphology relates to the dual function of providing support and mobility (visual/olfactory/auditory pursuit, oral prehension) to the head. The early notochord passes through the odontoid tip to the basiocciput surface before entering the clivus up to the craniopharyngeal canal; later, the rostralmost chordal remnant is the C2/3 nucleus pulposus. Chondrification starts in the second fetal month and ossification in the fetal or postnatal periods depending on the structure.
枕骨是体轴的上端，由天幕限制在颅侧。骨性颅颈连接（枕骨下部、寰椎和枢椎）位于未分节的枕骨和节段间的脊柱软骨体之间，分别通过 O4 和 C2 软骨体的节内裂隙与枕骨和 C3 隔开。它保留了原始的节段性弱中心（C1 的前弓），从枕骨下部 O4 到颅侧 C2 半软骨体（枢椎）不分节。它的形态与头部的支撑和活动（视觉/嗅觉/听觉追踪、口腔抓握）的双重功能有关。早期的脊索通过齿状突尖端进入基底部表面，然后进入斜坡，直到颅咽管；后来，最接近颅侧的脊索残余是 C2/3 椎间盘核。软骨化始于第二个胎儿月，骨化发生在胎儿期或出生后，具体取决于结构。
