The spinal cord is protected by bones, discs, ligaments, and muscles. The spine is made of 33 bones called vertebrae. The spinal cord passes through a hole in the center (called the spinal canal) of each vertebrae. Between the vertebrae there are discs that act as cushions, or shock absorbers for the spine. Ligaments and muscles help keep the vertebrae in the correct position. (Fig. 2)
There are many pathways or "tracts" in the spinal cord. The motor tracts in the spinal cord are found in the front of the middle parts of the cord. The nerve paths allow movement of the arms and legs. If there is damage to the motor tracts, weakness or being unable to move may occur below the level of damage (Fig. 3)
The sensory tracts in the spinal cord are found in the front and back parts of the cord. These nerve paths allow sensation. Damage to the front part of the spinal cord can result in loss of the ability to feel pain as well as hot and cold sensations below the level of damage. Damage to the back part of the spinal cord can result in loss of the ability to feel the sense of position of the arms or legs.