The spine extends from the head to the sacrum, and in most people consists of 24vertebrae. The vertebral column can be divided into three segments: Cervical The first seven vertebrae, all in the neck. These are smaller and lightly built. Thoracic Twelve vertebrae, each articulating with the twelve pairs of ribs. Lumbar The lower five vertebrae, between the ribs and the sacrum. These have the largest vertebral bodies. Each of the three segments of the spine has a curve. The cervical spine and the lumbar curve both are convex anteriorly, while the thoracic spine curves the opposite way, convex posteriorly. Each vertebra is shaped a bit like a wedge to support these curves, especially noticeable with the five lumbar vertebrae. The lumbar curve is unique to humans, allowing us to maintain a vertical posture above our pelvis.