A, The right half of the floor of the sphenoid sinus has been removed to expose the sellar floor and the part of the sphenoid sinus below the planum and tuberculum. On the specimen’s left side, the eustachian tube, pterygoid process, and posterior part of the maxillary sinus have been preserved. On the right side, the medial portion of the eustachian tube and the pterygoid process have been removed. This exposes the right mandibular nerve exiting the foramen ovale and the maxillary nerve exiting the foramen rotundum and passing forward as the infraorbital nerve. The pterygopalatine ganglion is located in the pterygopalatine fossa behind the maxillary sinus in the lateral wall of the nasal cavity. The right pterygoid process has been removed to expose the vidian canal, in which the vidian nerve travels to reach the pterygopalatine ganglion. The bone below the petrous carotid has been removed up to the point where the artery turns upward to enter the posterior part of the cavernous sinus. B, Part of the vomer, perpendicular ethmoid plate, and floor of the sphenoid sinus have been removed to expose the cavernous sinus, intracavernous carotid, and the pituitary gland. The floor of the optic canals have been removed to expose the ophthalmic arteries coursing below the optic nerves. The cavernous sinus surrounds the intracavernous carotid. An anterior intercavernous sinus crosses the anterior margin of the gland. Some of the upper clivus has been removed to expose the basilar sinus, which sits on the back of the dorsum and is the largest connection between the cavernous sinuses. C, The venous spaces around the pituitary gland have been cleared to expose the petrous and intracavernous carotid segments. D, Enlarged view of the pituitary gland, intracavernous carotid, and the optic nerves and ophthalmic arteries. The inferior hypophyseal arteries pass to the posterior lobe. The superior hypophyseal arteries arise in the chiasmatic cistern and pass medially to reach the stalk and chiasm. (Images courtesy of AL Rhoton, Jr.)