Atlas

Atlas (atlas), the name of the first cervical vertebra; more correctly, the Greeks called it epistropheus (epistrephomai - I turn), Tuberc. post. - because when turning the head, the atlas rotates along with it around the 'dens' of the second cervical vertebra, and not the latter, which incorrectly received this name. The term Atlas was proposed by Vesalius.

The axial, central part of the atlas body during development separates from it and fuses with the second vertebra, forming the upper part of its body and the dens, due to which the first vertebra receives an incorrectly ring-like shape; on the posterior part of it ('posterior arch'), the spinous process is underdeveloped (posterior tubercle); on the ventral surface of the anterior arch is the anterior tubercle (muscular). The powerful 'lateral masses' on the upper surface each have a joint fossa for articulation with the occipital condyles, forming an ellipsoid joint, in which movement of the head forward, backward, and to the sides occurs. The wide opening of the ring is crossed by the transverse ligament, which posteriorly embraces the 'dens'. At the point where the posterior arch arises from the lateral masses, there is a groove on each side for the arteria vertebralis.