Each typical vertebra presents two pairs of articular processes, which
form diarthroses with the two adjacent vertebræ. The =articular
surfaces= are extensive, flat, and oval in the cervical region, small
and flat in the thoracic region, while in the lumbar region the anterior
ones are concave and the posterior convex. The joint capsule is strong
and ample in the cervical region, in conformity with the large size and
greater mobility of these joints in the neck. In the thoracic and lumbar
regions the capsule is small and close. These joints are arthrodia.
Associated with these joints are the =ligamenta flava=, which connect
the arches of adjacent vertebræ. They are membranous and consist largely
of elastic tissue.
[Illustration: