The joints between the articular processes of the vertebrae belong to the arthrodial variety and are enveloped by capsules lined by synovial membranes.
While the laminae, spinous and transverse processes are connected by the following ligaments:
- The Ligamenta Flava: Inside the vertebral canal, posterior to the spinal cord is the ligamentum flavum (“yellow ligament”). This consists of a series of short, paired ligaments, each of which interconnects the lamina regions of adjacent vertebrae. The ligamentum flavum has large numbers of elastic fibers, which have a yellowish color, allowing it to stretch and then pull back. It provides important support for the vertebral column when bending forward.
- The Supraspinous Ligament is located on the posterior side of the vertebral column, where it interconnects the spinous processes of the thoracic and lumbar vertebrae. This strong ligament supports the vertebral column during forward bending motions. It is thicker and broader in the lumbar than in the thoracic region, and intimately blended, in both situations, with the neighboring fascia. The most superficial fibers of this ligament extend over three or four vertebrae; those more deeply seated pass between two or three vertebrae while the deepest connect the spinous processes of neighboring vertebrae. Between the spinous processes it is continuous with the interspinal ligaments. It is continued upward to the external occipital protuberance and median nuchal line, as the ligamentum nuchae.
- The Ligamentum Nuchae: In the posterior neck, where the cervical spinous processes are short, the supraspinous ligament expands to become the nuchal ligament (nuchae = “nape” or “back of the neck”). The nuchal ligament is attached to the cervical spinous processes and extends upward and posteriorly to attach to the midline base of the skull, out to the external occipital protuberance. It supports the skull and prevents it from falling forward. This ligament is much larger and stronger in four- legged animals such as cows, where the large skull hangs off the front end of the vertebral column. You can easily feel this ligament by first extending your head backward and pressing down on the posterior midline of your neck. Then tilt your head forward and you will fill the nuchal ligament popping out as it tightens to limit anterior bending of the head and neck.
- The Interspinal Ligaments thin and membranous, connect adjoining spinous processes and extend from the root to the apex of each process. They meet the ligamenta flava in front and the supraspinal ligament behind. They are narrow and elongated in the thoracic region; broader, thicker, and quadrilateral in form in the lumbar region; and only slightly developed in the neck.
- The Intertransverse Ligaments are interposed between the transverse processes. In the cervical region they consist of a few irregular, scattered fibers; in the thoracic region they are rounded cords intimately connected with the deep muscles of the back; in the lumbar region they are thin and membranous.
