Joints and Ligaments of the Vertebræ

Comparative Arthrology

Ox.—The ligamentum nuchæ is better developed than in the horse. The funicular part is clearly divided into two lateral halves, which are round at their occipital attachment, but from the axis backward become rapidly wider and flat. This wide portion is almost sagittal, lies on either side of the vertebral spines, and is covered by the trapezius and rhomboideus muscles. From the highest part of the withers (third thoracic spine) it gradually diminishes in size and fades out in the lumbar region. The lamellar part is thick, and consists of anterior and posterior parts. The anterior part is double; its fibers proceed from the funicular part to the second, third, and fourth cervical spines. The posterior part is single; its fibers extend from the first thoracic spine to the fifth, sixth, and seventh cervical spines.

The inferior common ligament is very strong in the lumbar region.

The intervertebral fibro-cartilages are thicker than in the horse.

The interspinous ligaments of the back and loins consist largely of elastic tissue.

There are no intertransverse joints in the lumbar region.

Pig.—The ligamentum nuchæ is represented by a fibrous raphé and thin layers of elastic tissue which extend between the cervical spines.

The atlanto-occipital and atlanto-axial joints resemble those of the dog.

The interspinous ligaments of the neck are elastic.

Dog.—The ligamentum nuchæ consists of a small fibrous band which extends from the spine of the axis to the anterior thoracic spines; it may be regarded as a mere fibrous raphé between the right and left muscles.

There are interspinous muscles instead of ligaments in the neck.

There are three ligaments in connection with the odontoid process. The two alar ligaments (Ligamenta alaria) arise on either side of the odontoid process, diverge, and end on either side of the foramen magnum. The transverse ligament of the atlas (Ligamentum transversum atlantis) stretches across the dorsal surface of the odontoid process and binds it down on the ventral arch of the atlas, a bursa being interposed. It is attached on either side to the lateral masses of the atlas.

The two capsules of the atlanto-occipital joint communicate with each other, and usually with the capsule of the atlanto-axial joint also.

Articulations of the Thorax

Ox.—The second to the eleventh costo-chondral joints inclusive are diarthroses with close capsules, reinforced externally. (They are synchondroses in the sheep.) The upper parts of the cartilages are attached to each other by distinct elastic ligaments (Ligamenta intercostalia).

The first pair of chondro-sternal joints are separate from each other; intercrossing fibers unite the costo-chondral junctions above the joints.

The first segment of the sternum forms a diarthrosis with the body. The anterior joint surface is concave, the posterior convex. The joint (Articulatio intersternalis) is surrounded by a close capsule, and the joint surfaces are attached to each by a small intraarticular ligament. Limited lateral movement is possible. (In the sheep the joint is a synchondrosis.)

Both surfaces of the sternum are covered by a layer of fibrous tissue.

Pig.—The second to the fifth or sixth costo-chondral joints are diarthroses. The intersternal articulation and the sternal ligaments resemble those of the ox.

Dog.—The first chondro-sternal joints do not coalesce.

The internal sternal ligament divides into three bands.