The adult spinal cord is about 50 centimetres long and extends from the base of the brain to about the waist. It is the major bundle of nerves that carry messages between the brain and the rest of the body. Nerves within the spinal cord (upper motor neurons) carry messages back and forth from the brain to the spinal nerves along the spinal tract. Lower motor neurons branch out from the spinal cord to the other parts of the body, carrying sensations (from the skin and other body parts and organs to the brain) and instructions (to the various body parts to initiate actions such as muscle movement).

Injury to the spinal cord causes loss of function of the nerves, limbs and organs below the site of the injury.

The spinal cord lies within vertebrae. These rings of bones are together called the spinal column or back bone. In general, the higher in the spinal column an injury occurs, the more dysfunction a person will experience.

There are seven vertebrae in the neck—the Cervical Vertebrae—C1 (at the top) to C7. Injury in this region usually causes loss of function to the arms and legs (quadriplegia or tetraplegia).

There are twelve Thoracic Vertebrae. The highest (T1) is where the top rib attaches. Injury to the thoracic region affects the chest and the legs.

Between the thoracic vertebrae and the pelvis lie the 5 Lumbar Vertebrae. The 5 Sacral Vertebrae run from the pelvis to the end of the spinal column. Injury to nerves in the lumbar and sacral vertebrae generally results in loss of functioning in the hips and legs.

Loss of function in the chest, hips and legs is Paraplegia.