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What is The joint between the atlas and axis is: and explain in detail?
First cervical vertebra is known as Atlas.
Second cervical vertebra is known as Axis.

Special joint between Atlas, Axis and Occipital bone:

Atlanto-Occipital joint:

It is a synovial joint - ellipsoid type.
Allows ﬂexion and extension of head on neck (as like nodding up and down).


Atlanto-Axial joint:

It is a pivot type of joint.
Allows rotatory movement of head on neck (as like saying 'NO' - right and left rotation).
The dens of axis forms a pivot, around which the atlas rotates, permitting rotatory motion of  neck possible.