G, The medial wall of the maxillary sinus has been removed to expose the sinus roof, which forms the orbital floor. The infraorbital sulcus and canal, which are situated in the floor of the orbit, form a prominence in the roof of the maxillary sinus. The anterior and posterior ethmoidal arteries arise from the ophthalmic artery and pass through the anterior and posterior ethmoidal canals to reach the floor of the anterior fossa beside the cribriform plate, where they again penetrate the bone to reach the walls of the nasal cavity. The vidian canal is the site of passage of the vidian nerve to the pterygopalatine ganglion. The vidian nerve is formed by parasympathetic fibers from the greater petrosal nerve and sympathetic fibers from the deep petrosal branch of the carotid plexus. H, Removing the lateral wall of the ethmoid air cells, which forms the medial wall of the orbit, exposes the periorbita. The frontal sinus is situated at the upper anterior part of the medial wall. The medial wall of the nasolacrimal duct has been removed to expose the interior of the duct. I, Enlarged view. The pterygoid process extends downward and forms the posterior wall of the pterygopalatine fossa. The medial pterygoid plate is situated beneath the nasopharyngeal mucosa just in front of the orifice of the eustachian tube. The greater and lesser palatine nerves arise from the pterygopalatine ganglion in the pterygopalatine fossa and are distributed to the palate, tonsil, and lining of the nasal cavity. J, The periorbita has been opened and some of the orbital fat removed to expose the medial and inferior rectus and superior oblique muscles. The annular tendon is the condensation of periorbita from which the rectus muscles arise. It surrounds the optic foramen and medial part of the superior orbital fissure. The lateral wall of the nasal cavity has been opened to expose the terminal part of the maxillary artery in the pterygopalatine fossa. K, The medial rectus muscle has been divided near the globe and reflected posteriorly. In this case, the ophthalmic artery courses below the optic nerve to reach the medial part of the orbit. The branch of the inferior division of the oculomotor nerve to the medial rectus muscle enters the medial side of the muscle. The ophthalmic artery gives rise to the anterior and posterior ethmoidal arteries as it courses near the superior oblique muscle. L, The ophthalmic artery has been retracted posteriorly to show the central retinal artery coursing below the optic nerve. Short ciliary arteries and nerves pass to the globe. (Images courtesy of AL Rhoton, Jr.)