Overview: Spinal Cord- Anatomy & Functions

If a person were to take a “slice” of the spinal cord horizontally, they would see a circular area in the middle covered in protective layers (the meninges). Extending from this circular area are nerve projections. These extend from the spinal cord to provide sensation to different areas in the body.

Key areas of a cross-section of the spinal cord include:

• Gray matter: The gray matter is the dark, butterfly shaped region of the spinal cord made up of nerve cell bodies.
• White matter: The white matter surrounds the gray matter in the spinal cord and contains cells coated in myelin, which makes nerve transmission occur more quickly. Nerve cells in the gray matter are not as heavily coated with myelin.
• Posterior root: The posterior root is the part of the nerve that branches off the back of the spinal column. Looking at the spinal cord cross-section, the top wings of the gray matter “butterfly” reach toward the spinal bones. The bottom wings are toward the front of the body and its internal organs.
• Anterior root: The anterior root is the part of the nerve that branches off the front of the spinal column.
• Spinal ganglion: The spinal ganglion is a cluster of nerve bodies that contain sensory neurons.
• Spinal nerve: The posterior and anterior roots come together to create a spinal nerve. There are 31 pairs of spinal nerves. These control sensation in the body, as well as movement.

The spinal cord does not extend for the entire length of the spine. It usually stops in the top parts of the lumbar spine.

For adults, this is usually the first or second lumbar vertebrae. Children’s spinal cords may stop slightly lower, at the second or third lumbar vertebrae.

What does the spinal cord do?

Your spinal cord carries nerve signals from your brain to the rest of your body and back. The signals are electrical messages that help almost everything in your body work correctly, including:

• Controlling your body’s movements and functions: Signals from your brain to other body parts let you move when you want to. They also control involuntary (autonomic) functions like your heartbeat and breathing. Involuntary functions happen automatically without you thinking about them.
• Reporting senses to your brain: Nerve signals from all over your body help your brain process and feel all of your senses, including pressure and pain.
• Managing your reflexes: Reflexes are automatic physical responses. The patellar reflex makes your lower leg kick forward when a healthcare provider taps your shin just below your kneecap (patella). Your spinal cord controls some reflexes without involving your brain.

Your spinal cord is like a much more important version of the cable that sends and receives your TV signal. Instead of transferring data back and forth about your favorite shows and movies, your spinal cord carries all the messages that help your body function and stay connected to your brain.

Spinal Cord vs. Vertebral Column

The spinal cord is often confused with the vertebral column, but the two are distinct. While the spinal cord is a soft layer of tissue consisting of nerves and cells, the vertebral column is a hard structure made of bone that covers the spinal cord and protects it.

Spinal Cord Conditions

Any disruption of spinal cord activity due to injury or disease could lead to serious conditions, including the loss of motor and sensory functions. In severe cases, this loss could be permanent.

• Spinal fractures. When the bones in the neck, spine, and back break, that can cause spinal fractures. Fractures can occur due to trauma, accidents, or genetic conditions.
• Spinal deformities. These can occur due to conditions such as scoliosis and kyphosis that cause abnormal curvatures in the spine. Such deformities can also occur due to spinal fractures or other conditions like spondylolisthesis and ankylosing spondylitis.
• Ankylosing spondylitis. This is a type of arthritis that causes inflammation between the bones in the spine. Sometimes, inflammation also occurs in the joints where the spine and your pelvis meet. Men are more likely to encounter this condition.
• Spondylosis. The spine’s vertebrae and the discs between the spinal cord bones wear out in cases of spondylosis, which can occur in the cervical region (in which case it is called cervical spondylosis) or in the lumbar and thoracic regions ( in which case it is called lumbar spondylosis or thoracic spondylosis, respectively).
• Spinal stenosis. The spine narrows due to injury or a disease such as osteoarthritis, putting undue pressure on the spinal cord and the nerves.
• Herniated discs. A herniated disc is a condition where one of the gel-like discs between the vertebrae breaks and puts pressure on one of the nearby nerves. This may lead to other conditions, such as sciatica and back pain.
• Degenerative disc disease. Also known as osteoarthritis of the spine, this is a condition where the discs between the vertebrae become dry and wear out. This typically occurs in old age, but impact injuries can also be the cause.
• Spinal tumors. When there’s an unusual tissue collection in and around the spinal cord or the spinal column, it may become a tumor. Malignant (cancerous) tumors are more harmful and can occur when tumors from other parts of the body spread to the spine.

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