Embryology Genetics homeobox (Hox) genes direct and regulate processes of embryonic differentiation and segmentation along the craniocaudal axis Osteology The cervical spine contains 7 vertebral bodies C1 (atlas) C2 (axis) C1 to C7 login to view 2 more bullets C2 to C6 login to view 1 more bullet C7 login to view 2 more bullets Alignment Normal sagittal lordosis (measured from C2 to C7) Spinal Canal Spinal canal normal diameter is 17 mm login to view 1 more bullet Atlas (C1) Has no vertebral body and no spinous process Embryology three ossification centers login to view 4 more bullets Articulations occiput-C1 login to view 2 more bullets Axis (C2) Osteology has an odontoid process (dens) and body embryology login to view 3 more bullets Kinematics C1-C2 (atlantoaxial) articulation login to view 4 more bullets C2-C3 joint login to view 4 more bullets C2 blood supply a vascular watershed exists between the apex and the base of the odontoid login to view 3 more bullets Occipital-C1-C2 Ligamentous Complex Provided by the odontoid process and its supporting ligaments transverse ligament login to view 1 more bullet apical ligaments login to view 1 more bullet alar ligaments login to view 1 more bullet Subaxial Cervical Spine (C3 to C7) C1 to C7 have a transverse foramen vertebral artery travels through transverse foramen of C1 to C6 C2 to C6 have bifid spinous processes C6 contains palpable carotid tubercle, which is a valuable landmark for the anterior approach to the cervical spine C7 non-bifid spinous process despite having a transverse foramen, the vertebral artery does NOT travel through it in the majority of individuals there is no C8 vertebral body, but there is a C8 nerve root The superior articular facets of the subaxial cervical spine (C3-C7) are oriented in a posteromedial direction at C3 and posterolateral direction at C7, with variable transition between these levels