The veins of the medulla spinalis (spinal veins, veins of the spinal cord) are situated in the pia mater

Pia mater

Pia mater often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. The word finds its roots in Latin, meaning literally "tender mother." The other two meningeal membranes are the dura mater and the arachnoid mater....

 and form a minute, tortuous, venous plexus.

They emerge chiefly from the median fissures of the medulla spinalis and are largest in the lumbar region.

In this plexus there are:

• (1) two median longitudinal veins, one in front of the anterior fissure, and the other behind the posterior sulcus of the cord.
• (2) four lateral longitudinal veins which run behind the nerve roots.

They end in the intervertebral veins

Intervertebral veins

The intervertebral veins accompany the spinal nerves through the intervertebral foramina; they receive the veins from the medulla spinalis, drain the internal and external vertebral plexuses.Their drainage depends upon the part of the body:...

.

Near the base of the skull they unite, and form two or three small trunks, which communicate with the vertebral veins, and then end in the inferior cerebellar veins

Inferior cerebellar veins

The inferior cerebellar veins are of large size, end in the transverse, superior petrosal, and occipital sinuses....

, or in the inferior petrosal sinuses.