The cranial pia mater covers the surface of the brain.

The membrane in this area is much thicker than the cranial pia mater, due to the two-layer composition of the pia membrane.

The cranial pia mater joins with the ependyma which lines the cerebral ventricles to form choroid plexuses that produce cerebrospinal fluid.

It is often broken down into two categories, the cranial pia mater (pia mater encephali) and the spinal pia mater (pia mater spinalis).