The Human Skeleton is the body's framework or scaffolding system. Skeletal bones are classified as long, short, flat, or irregular and vary in length, width, and depth. The bones in the spine are irregular in shape and provide places to connect to other bones. The function of the skeletal system is to support the body against the force of gravity, protect soft body parts, produce red blood cells, store inorganic calcium, and phosphorus salts, and to provide sites for muscle attachment to enable body movement.

The Spinal Column is also called the vertebral column. The bones in the spine are called vertebrae (ver-ta-bray). The column starts at the base of the skull and continues to the pelvis. Alternate layers of bone (vertebrae) and cartilage (car-til-ledge, the intervertebral discs) stack vertically one on top of the other in the spinal column. The lattice-like structure of the cancellous bone (cancel-lus, the spongy interior) in a vertebra absorbs external pressure.

Five Cervical vertebrae follow below the atlas and axis. The Thoracic spine is located in the chest area and contains 12 vertebrae. The ribs connect to the thoracic spine and protect many vital organs. Next is the Lumbar spine. Most people have five lumbar vertebrae although it is not unusual to have six. The lumbar vertebrae are larger than the cervical or thoracic as this spinal region carries most of the body's weight. The sacrum and coccyx are uniquely shaped.

Medical professionals often abbreviate the levels (vertebrae) of the spinal column. For example, the seven cervical vertebrae are C1, C2, C3, C4, C5, C6 and C7. The thoracic levels are T1, T2, and T3 through T12. Similarly the lumbar levels are L1 through L5 (or L6).

The sacrum is simply S1. The coccyx is not abbreviated or numbered. With the exception of the atlas, axis, sacrum and coccyx, each cervical, thoracic, and lumbar vertebra is similarly shaped.

Slika 1 - 1. Sacroiliac, Joint 2. Coccyx (tailbone), 3. Sacrum