identify the articulation site that allows us to nod our head yes.
The first cervical vertebra is called the atlas. The atlas looks like a ring of bone. It lacks a body. But it has front and rear arches that connect to the sides of bony enlargements called lateral masses. These masses contain the transverse foramina and articular surfaces that attach to the next vertebra and the base of the skull.
The synovial joints between the atlas and the skull allow a person to nod his head yes.
There are many types of vertebral joints, but the atlas and axis form the only craniovertebral joints in the body. A craniovertebral joint is exactly what it sounds like: a joint that permits movement between the vertebral column and the skull.
The ligaments in the spine support and reinforce the joints between the vertebrae. The atlas and axis in particular work with the ligaments to move the neck. The atlas and the occipital bone form the atlanto-occipital joint, which allows neck flexion. When you nod your head as if to say “yes,” that is neck flexion. The atlas and axis form the atlanto-axial joint, which allows head rotation. If you shake your head as if to say “no,” that is head rotation.