or spinal column or spine or backbone
Flexible column extending the length of the torso.
In humans, it consists of 3234 vertebrae, with different shapes and functions in each of five regions: 7 cervical, in the neck (including the atlas and axis, modified for free movement of the skull ); 12 thoracic, in the chest; 5 lumbar, in the lower back; 5 sacral (fused into the sacrum, part of the pelvic girdle); and 3 to 5 coccygeal (vestigial tailbones fused into the coccyx). The body of each vertebra is separated from its neighbours by cushioning intervertebral disks of cartilage . Behind the body is a Y-shaped vertebral (neural) arch with structures extending up and down to form joint s with the adjacent vertebrae and to the back and sides to provide attachment points for muscle s and ligament s. The spine supports the torso and protects the spinal cord .