Anatomy of the vertebral canal

When they say to watch your back, you really should, because there is something pretty important in there called the spinal cord. Now, if you think of a nerve as a road, then the spinal cord is a huge highway.

It’s a major reflex center and holds many neural tracts that connect the brain to the rest of the body, allowing for important communication to occur.

The spinal cord starts at the foramen magnum, where it is continuous with the medulla oblongata, which is the most caudal portion of the brainstem.

It then extends inferiorly through the vertebral canal. In adults, it usually ends at the level of the first or second lumbar vertebra.

In infants, it usually ends at the second or third lumbar vertebra. The tapered end of the spinal cord is called the conus medullaris.

If we look at a transverse section of the spinal cord, we can see the anterior median fissure that extends along the midline of the spinal cord, anteriorly. Similarly, the posterior median sulcus extends along the midline of the spinal cord, posteriorly.

The spinal cord can be divided into spinal cord segments. One spinal cord segment gives rise to the anterior and the posterior nerve roots, which come together to form a spinal nerve on each side of the spinal cord.

There are 31 spinal cord segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. A spinal nerve pair shares its name with the spinal cord segment it arises from.

So for example, the spinal nerves arising from the C1 spinal cord segment are named the C1 spinal nerves. Logically, the number of paired spinal nerves is the same as the number of spinal cord segments.

Now, not all regions of the spinal cord are the same size. There are two regions that carry more fibers and are therefore wider, resulting in two spinal cord enlargements.

The cervical enlargement spans the C4 through T1 segments. The anterior rami of the spinal nerves that arise from most of these segments form the brachial plexus which provides innervation for the upper limbs.