Walsh & Hoyt: Dura Mater

The dura mater, typically referred to as the dura, is a thick membrane that is adjacent to the inner table of the skull and acts both as the functional periosteum of the skull and the outermost membrane of the brain. In the spinal canal, this dura is separated from bone by a space that contains epidural adipose and areolar tissue. At the orbital end of the optic canal, the dura encloses the intracanalicular portion of the optic nerve and splits into an inner layer that becomes the dural sheath surrounding the orbital portion of the optic nerve and an outer layer that becomes the periosteum of the walls of the orbit, the periorbita.