Dural layers of the pituitary gland. The two dural layers are attached one to the other at the level of the sellar face, but they split at the parasellar region to form the cavernous sinus. The periosteal or outer dural layer of the pituitary gland has been partially removed. This layer forms the anterior wall of the cavernous sinus and is continuous with the dura of the tuberculum sella and anterior skull base. The meningeal or inner dural layer surrounds the gland and forms the medial wall of the cavernous sinus. The cavernous sinus is precisely the venous cavity formed by the separation of the periosteal and meningeal dural layers. (Image courtesy of JC Fernandez-Miranda)