Final answer:
The occipital condyles of the occipital bone articulate with the atlas to form the atlantooccipital joint, enabling flexion and extension of the head.
Step-by-step explanation:
The part of the occipital bone that articulates to form the atlantooccipital joint is known as the occipital condyles. Located on either side of the foramen magnum at the base of the skull, these oval-shaped structures form joints with the first cervical vertebra, the atlas (C1). This articulation allows considerable flexion and extension of the head, permitting movements such as nodding "yes". Unlike the atlantoaxial joint, which allows rotation of the head as in shaking "no", the orientation of the articular processes in the atlantooccipital joint largely prohibits rotation.