Dura mater is inflexible and extends from the foramen magnum to S2 of the spinal cord. The two sublayers of the dura mater include the outer periosteal layer and inner meningeal layer. The tissue helps separate the cranial cavity into compartments to protect the brain. The falx cerebri separates cerebral hemispheres. The falx cerebelli separates lobes of the cerebellum. The tentorium cerebelli separates the cerebrum from the cerebellum. To protect the brain, the dura mater contains several sinuses that carry blood back to the heart. These are the superior sagittal, straight, inferior, and transverse sinus. The dural space lies between the dura mater and skull. The subdural space lies between the dura and arachnoid mater.