In humans the epidural space contains lymphatics, spinal nerve roots, loose connective tissue, adipose tissue, small arteries, dural venous sinuses and a network of internal vertebral venous plexuses.

The two layers of the dura mater separate at several places, with the meningeal layer projecting deeper into the brain parenchyma forming fibrous septa that compartmentalize the brain tissue.

[2][4][5] There are four fibrous septa:[4] In pathological conditions fluid such as blood can fill this space.

[6] Epidural space is the smallest at the cervical region, measuring 1 to 2 mm.

[7] However, some authors stated that it decreases in size after mid-lumbar region until 2 mm at S1 level.