Superior view of orbits and intervening ethmoid sinuses. The orbital plates of the frontal bone and underlying periorbita have been removed to show contents of the orbits. Coursing superficial to the levator palpebrae superioris muscles from the orbital apex toward the base are the frontal nerves. These divide into larger supraorbital (laterally) and smaller supratrochlear (medially) branches. Deep to the levator palpebrae muscles are the superior rectus muscles. Both are supplied by the oculomotor nerve. The medial walls of the orbit are parallel and longer than their lateral walls. Two muscles are located along the medial wall. The more superior of the two is the superior oblique muscle whose tendon is redirected by a fibrocartilaginous "pulley" backward and laterally to the globe. It receives its motor supply from the trochlear nerve, which enters the orbit just medial to the frontal nerve. Below this muscle is the medial rectus. Emerging between these two muscles are the anterior ethmoidal artery and nerve, which traverse and supply ethmoidal air cells before entering the nasal cavity. The lateral rectus follow the lateral wall of the orbit to the eyeball. The lacrimal nerve, artery, and vein course along its superior border to the lacrimal gland. The superior ophthalmic vein originates near the upper medial aspect of the orbit and and generally parallels the course of the ophthalmic artery crossing the optic nerve from medial to lateral to drain much of the orbit to the cavernous sinus. The ophthalmic arteries and optic nerves enter the orbits via the optic canals. Immediately medial to the medial walls of the orbits are the honey-combed arrangement of ethmoid air cells. Posterior to these are the sphenoid sinuses. In the midline is the cribriform plate of the ethmoid bone upon which lay the olfactory bulbs and tracts conveying sensory information of smell from the olfactory epithelium and nerves. (Image courtesy of AL Rhoton, Jr.)