Atlantooccipital membrane can be
- Anterior atlantooccipital membrane
- Posterior atlantooccipital membrane
The anterior atlantooccipital membrane or anterior atlantooccipital ligament is broad and has dense woven fibers. The fibers pass between the anterior margin of the foramen magnum above, and the upper border of the anterior arch of the atlas below.
Laterally, it is continuous with the articular capsules.
In front, it is strengthened in the middle line by a strong, rounded cord, which connects the basilar part of the occipital bone to the tubercle on the anterior arch of the atlas.
The posterior atlantoöccipital membrane posterior atlantooccipital ligament is broad but thin, is connected above, to the posterior margin of the foramen magnum; below, to the upper border of the posterior arch of the atlas.
This membrane is defective below on the either side, over the groove for the vertebral artery, and forms with this groove an opening for the entrance of the artery and the exit of the suboccipital nerve.