4. INDIVIDUAL TYPES OF VERTEBRAE

1. Cervical vertebrae.

The cervical part is situated in the upper part of the spine. It is one of the most mobile parts of the spine. Thanks to this part a person can move his neck.

The bodies of the cervical vertebrae are transverse-oval in shape, and the upper and lower surfaces are concave. The anterior tubercle of the sixth vertebrae is enlarged and is called the carotid tubercle (the carotid artery can be compressed against it to arrest bleeding). The seventh vertebra is distinguished by a large spinous process.

The first and second cervical vertebrae have a specific shape because they form the mobile articulation with the skull. Most of the body of the first vertebra remains separate and joins the second vertebra as a tooth-like process.

2. Thoracic vertebrae articulate with the ribs.

The thoracic part is connected with the back wall of the thorax. The ribs are joined with the thoracic vertebrae with the help of joints. The mobility of the thoracic part of the spine is limited because of the low height of interver-tebral discs and significant length of spinous processes of the vertebrae.

The spinous processes of the thoracic vertebrae are long and are inclined sharply downward. Such direction of the processes limits extension of the spine here, which is a protective accommodation for the heart.

Lumbar vertebrae are distinguished by a massive body since they carry weight. The spinous processes are directed horizontally, to the back.

3. Sacral vertebrae fuse in youth to form a single bone, the sacrum. This fusion is an adaptation to the considerable load carried by the sacrum because of the upright posture of the human. The sacrum is triangular in shape, and its base faces upward, while the apex faces downward.