Vertebral column is also called backbone or spine. It consists of a row of 33 movably articulated, ring - like bones, the vertebrae. The vertebrae are grouped into five groups cervical vertebrae - 7 in number, present in the neck; thoracic vertebrae - 12 in number, present in the chest; lumbar vertebrae - 5 in number, present in the abdomen; sacrum - the 5 sacral vertebrae are fused in the adult, forming one structure called the sacrum, which lies between the innominate bones of the pelvic girdle; coccyx - the 4 coccygeal vertebrae are fused to form a curved triangular bone, called the coccyx. Vertebral column displays four curves to enhance balancing powers and firmness for upright posture of the body. These curvatures are cervical, thoracic, lumbar and pelvic (= sacral).