Atlas (anatomy) - Vertebral Foramen

Vertebral Foramen

Just below the medial margin of each superior facet is a small tubercle, for the attachment of the transverse atlantal ligament which stretches across the ring of the atlas and divides the vertebral foramen into two unequal parts:

• the anterior or smaller receiving the odontoid process of the axis
• the posterior transmitting the spinal cord (medulla spinalis) and its membranes

This part of the vertebral canal is of considerable size, much greater than is required for the accommodation of the spinal cord.

The transverse processes are large; they project laterally and downward from the lateral masses, and serve for the attachment of muscles which assist in rotating the head. They are long, and their anterior and posterior tubercles are fused into one mass; the foramen transversarium is directed from below, upward and backward.