The vertebrae articulate together by their bodies and the transverse processes. Each individual joint has not much power of movement, but, taken altogether, the range of movement of the spine as a whole is considerable.

Intercentral Articulations

These take place between the flattened surfaces of the bodies of the vertebrae. Between the two surfaces is a cartilaginous disc, the intervertebral disc. In the cervical and lumbar region the disc is thicker in front than behind, and the reverse in the dorsal, thus helping to form the curves.

The Anterior Longitudinal ligament runs the whole length of the spinal column on the anterior surface, from the first cervical vertebra to the upper margin of the sacrum, and is firmly attached to the intervertebral discs as it passes over them.

The Posterior Longitudinal ligament resembles the foregoing, but is placed inside the spinal canal on the posterior surfaces of the bodies.

Interneural Articulations

These take place between the articulating processes on the pedicles of adjacent vertebrae. These are gliding joints, each surrounded by a thin capsule lined by a synovial membrane. In addition, the ligamenta flava binds together the laminae. This ligament is inside the spinal canal, and resembles the anterior and posterior longitudinal ligaments in being continuous throughout the length of the spinal column.

The spinous processes are attached to one another by inter-spinous ligaments. In continuity with them are the supraspinous ligaments, which extend all along the spinal column from tip to tip of the spines. In the cervical region these are particularly developed, forming a partition between the muscles of the two sides, and called the ligamentum nuchae.

The atlas and the axis have several additional ligaments joining them together, one being a transverse ligament, which is attached to the dorsal surface of the anterior arch of the axis, and passes behind the odontoid peg of the axis.

The spinal column as a whole is freely movable, and permits of movement round three axes Transverse - flexion and extension.

Antero-posterior - lateral flexion.

Vertical - rotation.

Fig. 34. - Vertebral Ligaments.

The articulations of the ribs, both with the vertebrae and the sternum, are by means of gliding joints, which allow the ribs to be raised and lowered by the muscles to perform the act of breathing.