Vertebral Column: Regions and Curvature

In humans, the vertebral column or spine is a flexible segmented column comprising a series of bones called vertebrae that protect the spinal cord.

The spine supports the head and is an attachment site for the bones of the rib cage and muscles.

In an infant, the spine has thirty-three vertebrae, while the adult spine has only twenty-six. Three major regions are common between infants and adults: the cervical region, with C-1 to C-7 vertebrae, followed by the thoracic and lumbar regions, having T-1 to T-12, and L-1 to L-5 vertebrae.

The five sacral and four coccygeal bones in infants are fused in adults to form the lower sacrum and coccyx regions. 

The vertebrae size gradually increases from the cervical to the lumbar region, helping  the spine distribute body weight.

The characteristic S-shape of the vertebral column is due to four curvatures. The posterior convex thoracic and sacral curvatures are present from birth, and the posterior concave cervical and lumbar curvatures develop later as an infant grows.