Joint Atlantoaxial Median

The atlantoaxial median joint (lat. a. atlantoaxialis mediana, pna) is the joint between the atlas tooth and the anterior arch of the atlas on one side and the body of the axis on the other. This is a cylindrical joint that provides rotational movements of the head around a vertical axis.

Articulating surfaces of the joint:

1. Below: the upper surface of the body of the axis with the condyle for the atlas tooth.
2. From above: the lower surface of the atlas tooth and the anterior arch of the atlas.

Movements in this joint:

1. Flexion and extension of the head (nodding movements).
2. Turn your head right and left (rotational movements).

The articular capsule of the joint is strengthened by the anterior and posterior atlantoaxial ligaments. The joint has synovial fluid and cartilage covering the articulating surfaces to facilitate movement.

The medial atlantoaxial joint plays an important role in the mobility of the cervical spine and head. Damage to this joint can lead to impaired movement of the head and neck.

The atlanto-occipital joint is motionless, in front it is limited by the tooth of the axial bone and the lower edge of the arch of the atlas, and behind by the lateral mass of the occipital bone and the basilar part of the occipital squama. There are two canals in it: the unpaired posterior one - the canal of the vertebral artery - emerges on the surface of the cranium in the occipital foramen, the unpaired superior one - the canal of the hypoglossal nerve - flows into the foramen magnum at the level of the upper border of the ala atlantae. Due to the tight fixation of the intervertebral discs, the location of the serrated semi-axes of the atlas to the anterior edges of the anterior arches, the lateral masses of the skull to the posterior edges of the posterior arches of the cranial and odontoid processes of the atlas, and the small size in relation to the length of the skull body, displacement of the first cervical vertebra relative to the axial odontoid line of the skull is practically impossible . Therefore, the joint has little importance in the fixing functions of the skull.

The main importance of this joint is in the functioning and innervation of the tongue, supplied through the hypoglossal and glossopharyngeal branches of the IX and X cranial nerves.