Osteology of the spine (vertebral column) The vertebral column in an adult typically consists of 33 vertebrae arranged in five regions: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal. Significant motion occurs only between the 25 superior vertebrae. Of the 9 inferior vertebrae, the 5 sacral vertebrae are fused in adults to form the sacrum, and after approximately age 30, the 4 coccygeal vertebrae fuse to form the coccyx. The vertebral column extends from the cranium (skull) to the apex of the coccyx. In the adult it is 72–75 cm long, of which approximately one quarter is formed by the IV discs that separate and bind the vertebrae together. The vertebrae gradually become larger as the vertebral column descends to the sacrum and then become progressively smaller toward the apex of the coccyx. The change in size is related to the fact that successive vertebrae bear increasing amounts of the body’s weight as the column descends. The vertebrae reach maximum size immediately superior to the sacrum, which transfers the weight to the pelvic girdle at the sacroiliac joints. Cervical vertebrae: form the skeleton of the neck. The cervical vertebrae are located between the cranium and the thoracic vertebrae. Their smaller size reflects the fact that they bear less weight than do the larger inferior vertebrae. Although the cervical IV discs are thinner than those of inferior regions, Cervical vertebrae: there are seven (7) cervical spine (C1- C7). C1 and C2 are ATYPICAL and C3 – C7 are TYPICAL. The C1 vertebra is called ATLAS and shows absent of absent of vertebral body and spinous process. and the second C2 vertebra is called the AXIS and odontoid process. The C3 to C7 is the normal vertebrae. The C7 has the longest spinous process which can be felt in the posterior aspect of the neck when flexion. C7 is called VERTEBRA PROMINENS. Thoracic vertebrae: there are twelve (12) thoracic spine, they are located in the thoracic region and interpose the cervical and lumbar vertebrae. Each thoracic spine has an articulation with a rib posteriorly. The vertebral bodies are thicker/bigger as compared to the cervical spine and less thick as compared to the lumbar vertebral bodies. Lumbar vertebrae: are in the lower back between the thorax and sacrum. It’s five in number. Because the weight they support increases toward the inferior end of the vertebral column, lumbar vertebrae have massive bodies. Sacrum: The wedged-shaped sacrum (L. sacred) is usually composed of five fused sacral vertebrae in adults. It is located between the hip bones. The sacrum provides strength and stability to the pelvis and transmits the weight of the body to the pelvic girdle, the bony ring formed by the hip bones and sacrum, to which the lower limbs are attached. Coccyx: (tail bone) is a small triangular bone that is usually formed by fusion of the four rudimentary coccygeal vertebrae, although in some people, there may be one less or one more.