The human spine – also at times called the spinal column, vertebral column, or just the backbone – is a flexible bony column that extends from the base of the skull to the small of the back. It serves two main purposes:
Working together with various muscles and ‘girdles’ – the latter being encircling or arching arrangements of bones, such as the pelvic and shoulder girdles – the spine provides the support that enables us to stand upright.
It also encloses – and so protects to a large extent – the spinal cord, that portion of the central nervous system whose nerve cells and bundles connect all parts of the body with the brain. Structurally, the spine consists of a number of vertebrae (or
individual bones) that are stacked on top of each other and separated as well as connected by discs of fibrocartilage (the intervertebral discs, which are discussed later in this chapter).
Although adults have 26 vertebrae, new-born babies have 33, nine of those extra ones becoming eventually fused into two separate single bones. An adult spine has five regions, consisting of the following, and starting from the bottom up:
Four fused coccygeal – or tail – vertebrae, which together make up the coccyx.
Five fused sacral vertebrae, which form the sacrum.
Five lumbar – or lower back – vertebrae.
Twelve thoracic (also at times called thoriac) – or chest -vertebrae.Seven cervical – or neck – vertebrae.