What is regarded as the first third of the spine?

The cervical spine is considered the first third of the spine due to its location at the top of the spinal column. It consists of seven vertebrae, labeled C1 to C7, and serves as the connection between the skull and the rest of the spine. This region is responsible for supporting the head, protecting the spinal cord, and allowing for a range of motion in the neck.

The thoracic spine, which follows the cervical spine, consists of twelve vertebrae and is primarily involved in articulating with the ribs and forming the upper back. The lumbar spine, situated below the thoracic spine, contains five vertebrae and bears much of the body's weight, making it crucial for movements like bending and lifting. The sacral spine is located at the base of the vertebral column and consists of fused vertebrae that contribute to the pelvic structure, but it does not represent the uppermost section. The cervical spine's unique role in supporting the head and facilitating neck mobility distinguishes it as the first third of the spine.