Anatomy of the Spinal Cord

The spinal cord is part of the central nervous system. It relays sensations to the brain, and allows the brain to control movements and function of the internal organs, trunk, and arms and legs. The spinal cord is made up of bundles of nerves The spinal cord carries signals from your body to your brain, and vice versa.

The spinal cord is tube-shaped and extends from the brain all the way down to the top of the lumbar spine, or the lower region of the spine. Branching off from the spinal cord are small nerves called nerve roots. These roots come out from small spaces between the bones (vertebrae) that surround the spinal cord and run to different parts of the body.

The entire spinal cord is surrounded by a liquid called cerebrospinal fluid, or CSF. CSF protects the spinal cord from injury. The spinal cord is also protected by 3 layers of coverings called the meninges. They are the dura mater, the arachnoid mater, and the pia mater.

The spinal cord and spine are divided into 4 regions from top to bottom: cervical, thoracic, lumbar, and sacral. Damage to the nerves in the spinal cord can result in many health conditions, depending on the region that is affected.

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Cervical region

This portion of the spinal cord contains nerve roots that connect to the upper body, arms, and hands. Nerves going to and coming from the lower parts of the body have to pass through the cervical spinal cord. These nerves are bundled into tracts. Between the vertebrae in the spine are spongy cushions called intervertebral disks. If the disks collapse, they may squeeze (pinch) the nerves in the cervical spine. This can lead to a condition called cervical radiculopathy. This condition can cause pain, weakness, or numbness in the arms. If the cervical region is severely injured, such as when the tracts are injured, most of the body can be paralyzed (quadriplegia). This can also lead to loss of control of some organs such as bowel and bladder control. Severe injuries can occur from a fall or from certain health conditions. These conditions include a herniated disk. This is when the spongy cushion slips out, pressing against nearby nerves. Another condition is spinal stenosis, where the spinal canal narrows and pinches the nerves.

Thoracic region

The nerve roots in the thoracic spinal cord run to the chest and stomach and control movement in those parts of the body. Serious injuries to the thoracic region of the spinal cord can lead to paraplegia. This is paralysis of the lower part of the body.

Lumbar region

The lumbar spinal cord is the lower area of the back. Nerve roots coming from the spinal cord in the lumbar spine control the legs. The lumbar region is where the spinal cord ends (the spinal cord is shorter than the spine). After the lumbar spinal cord ends, it continues as a bundle of nerve roots in the lower back (the cauda equina). An intervertebral disk in the lumbar spine may herniate or move into the space containing a nerve root. This can cause lower back pain or lower extremity pain (lumbar radiculopathy). In severe cases, it can cause cauda equina syndrome. This is a serious condition that compresses the sacral nerve roots. This causes inability to empty the bladder (urinary retention), constipation, loss of feeling in the groin (saddle anesthesia), and weakness or paralysis of the legs or feet. 

Sacral region

The lowest part of the spinal cord contains 5 pairs of nerves. These control the thighs, lower legs, and the genital and anal areas. Sacral nerve injury can happen anywhere from the upper lumbar spine down to the sacrum. This can lead to lower back pain, urinary incontinence or retention, loss of feeling in the foot, and sexual dysfunction. 

Keeping your spinal cord healthy

Some spinal cord injuries can’t always be avoided, such as those caused by car accidents. But you can take many steps to preserve the health of your spine and the spinal cord nerves within it. Car crash injuries may be reduced by correctly using seat belts and air bags. Staying at or reaching a healthy weight is suggested because excess pounds can put unneeded stress on your back. It's also important to maintain good posture, stretch and take part in physical activities that strengthen your back muscles. To strengthen the bones of your spine and protect your spinal cord, a vitamin D-rich diet is also essential. Finally, know your limits and avoid picking up items that are too heavy for you to lift safely. Use correct lifting techniques.