The seventh by the long spinous process and the slender simple transverse process, and by the usual absence of the foramen transversarium.
LIGAMENTS OF THE VERTEBRAL COLUMN.
Fibro-cartilagines intervertebrales.—The separate vertebræ (except the atlas and axis) are united by the disk-shaped intervertebral fibro-cartilages, which are situated between the centra of the vertebræ. Each consists of a central pulpy portion and a fibrous outer portion, covered by strong intercrossing tendinous fibers which unite with the periosteum of the vertebræ.
Ligamentum longitudinale anterius.—On the ventral face of the centra of the vertebræ, from the atlas to the sacrum, lies a longitudinal ligament, the anterior longitudinal ligament. It is very small, almost rudimentary, in the cervical region: large and strong in the thoracic and lumbar regions.
Ligamentum longitudinale posterius ([Fig. 14], a).—A corresponding ligament (posterior longitudinal ligament) lies on the dorsal surface of the centra (therefore within the vertebral canal). It is enlarged between each pair of vertebræ and closely united to the intervertebral fibro-cartilages.
Ligamentum supraspinale.—Between the tips of the spinous processes of the thoracic and lumbar vertebræ extend ligamentous fibers. They are not united to form a distinct band, and can hardly be distinguished from the numerous tendinous fibers of the supraspinous muscles. Together they represent the supraspinous ligament. From the tip of the spinous process of the first thoracic vertebra to the caudal end of the spine of the axis extends a slender strand representing the ligamentum nuchæ or cervical supraspinous ligament. It is imbedded in the superficial muscles of this region, some of which take origin from it.
Ligamentous fibers are also present between the spinous processes of the vertebræ (ligamenta interspinalia): between the transverse processes (ligamenta intertransversaria), and between the vertebral arches (ligamenta flava).
Capsulæ articulares.—The joints between the articular processes are furnished with articular capsules attached about the edges of the articular surfaces. These are larger and looser in the cervical region.
Atlanto-occipital Articulation.—The joint between the atlas and the occipital condyles has a single articular capsule, which is attached about the borders of the articular surfaces of the two bones. This capsule is of course widest laterally, forming indeed two partially separated sacs, which are, however, continuous by a narrow portion across the ventral middle line. This capsule communicates with that which covers the articular surface of the dens, and through this with the capsule between the atlas and axis. That portion of the capsule which covers the space between the ventral arch of the atlas and the occipital bone represents the anterior atlanto-occipital membrane; it is strengthened by a slender median ligamentous strand. The posterior atlanto-occipital membrane covers in the same way the space between the dorsal arch of the atlas and the dorsal edge of the foramen magnum. In it a number of different sets of fibers, with regard to direction and to degree of development, may be distinguished; these have sometimes been considered separate ligaments.
The lateral ligaments of the atlas begin at the lateral angle of the cranial margin of the atlas, at about the junction of its dorsal and ventral arches, and pass cranioventrad to the jugular processes.