A, The lateral wall and roof of the right orbit and the intraorbital fat have been removed. The anterior clinoid process and dura in the lateral wall of the cavernous sinus have been preserved. The oculomotor, trochlear, and ophthalmic nerves have been exposed by removing the dura in the lateral wall of the cavernous sinus. The superior and inferior ophthalmic veins arise inside the muscle cone, but exit the intraconal area as they converge on the orbital apex. The superior ophthalmic vein passes downward along the origin of the lateral rectus muscle from the annular tendon, where it is joined by the inferior ophthalmic vein to form a common trunk that passes backward below and medial to the ophthalmic nerve to enter the cavernous sinus. B, Another specimen with the anterior clinoid, lateral wall of the orbit, and cavernous sinus removed. The superior ophthalmic vein exits the muscle cone to pass along the lateral margin of the superior orbital fissure and below the ophthalmic nerve (blue arrow) to enter the anteroinferior part of the cavernous sinus on the medial side of the ophthalmic nerve. C, The superior ophthalmic vein has been removed. The trochlear nerve passes medially above the oculomotor and ophthalmic nerves to reach the superior oblique muscles. The frontal, lacrimal, and trochlear nerves pass outside the annular tendon, and the nasociliary, oculomotor, and abducens nerves pass through the tendon. D, The frontal and lacrimal nerves have been depressed to show the nasociliary nerve arising from the medial side of the ophthalmic nerve. The oculomotor foramen is the portion of the opening in the annular tendon lateral to the optic foramen through which the superior and inferior divisions of the oculomotor nerve and the nasociliary and abducens nerves pass. The oculomotor nerve divides into superior and inferior divisions just behind the superior orbital fissure and annular tendon. The abducens nerve courses on the medial side of the ophthalmic nerve in the cavernous sinus, but in the fissure, it turns laterally below the nerve to enter the medial side of the lateral rectus muscle. E, The annular tendon has been divided between the origin of the superior and lateral rectus muscles. The superior division of the oculomotor nerve passes upward to innervate the levator and superior rectus muscles. The inferior division innervates the inferior oblique, inferior rectus, and medial rectus muscles and gives rise to the parasympathetic pupilloconstrictor fibers to the ciliary ganglion. F, Another specimen to show the oculomotor nerve splitting into the superior and inferior divisions at the anterior edge of the cavernous sinus just behind the superior orbital fissure. (Images courtesy of AL Rhoton, Jr.)