The spine is a column of small bones or vertebrae that support the entire upper body. The column is grouped into three sections of paragraphs:
• Cervical vertebrae (C) are the bones of the cervical spine and consist of seven vertebrae that support the neck and head.
• The thoracic vertebrae (T) are twelve spinal bones connected to the rib cage.
• The lumbar vertebrae (L) are the five lowest and largest bones in the spine. Most of the body weight and pressure falls on the lumbar vertebrae.
• At the bottom of the lumbar vertebrae lies the sacral vertebrae, which is a skeleton in the form of a shield that connects to the pelvis at the sacroiliac joints.
• At the end of the sacrum there are two to four small vertebrae partially fused known as the coccyx or "tail bone".
• Each paragraph can be identified using a letter and a number; The letter reflects the region (C = neck, T = chest, L = lower back, and S = sacrum), and the number indicates its location within that region. For example, C4 is the fourth lowest bone in the cervical vertebrae, and T8 is the eighth thoracic vertebra.
• The vertebrae in the spine are separated from each other by small cushions of cartilage known as intervertebral discs, known to people as vertebral cartilage. Inside each disc is a gel-like substance surrounded by a fibrous structure. The disc is 80% water, which makes it very flexible.
• Each vertebra in the spine contains a number of bony projections, known as processes. Spinal processes and transverse processes are connected to the muscles in the back and act like little levers, allowing the spine to twist or bend. The articular processes form the joints between the vertebrae themselves, they meet together and intertwine.
• Each vertebra and its processes surround and protect a central opening in the form of an arch. These arches, aligned down the spine, form the spinal canal, which surrounds the spinal cord, the central stem of the nerves that connect the brain to the rest of the body.
• The upper torso usually has a gentle external curve (kyphosis) while the lower back has a reverse internal curve (lordosis).