A, Sagittal section to the left of the midline and nasal septum. The nasal septum is formed anteriorly by the septal cartilage, above by the perpendicular plate of the ethmoid, and below and posteriorly by the vomer. The posteroinferior part of the septum is supplied by the branches of the sphenopalatine artery, a terminal branch of the maxillary artery. The upper part of the septum, below the cribriform plate, is supplied by the branches of the ethmoidal arteries, which arise from the ophthalmic artery. A septum divides the sphenoid sinus near the midline. The optic chiasm, optic and oculomotor nerves, third ventricle, and pituitary stalk are located above the pituitary gland. The gyrus rectus of the frontal lobe is located above the cribriform plate and olfactory tract. B, Midsagittal section of the sphenoid sinus and pituitary gland. Prominences overlie the optic canal, internal carotid artery, superior orbital fissure, and maxillary nerve in the wall of the sphenoid sinus. The opticocarotid recess extends laterally between the optic nerve, internal carotid artery, and the prominence passing through the superior orbital fissure, and extends into the optic strut, which separates the optic canal from the superior orbital fissure. The serpiginous prominence overlying the internal carotid artery is located anterior to and below the pituitary gland. C, The lateral wall of the nasal cavity is constituted below by the nasal surface of the maxilla and above by the nasal surface of the ethmoidal sinuses. The inferior concha (turbinate) is an independent bone, that articulates with the nasal surface of the maxilla and the perpendicular plate of the palatal bone. The middle and superior concha are appendages of the ethmoid bone. The lacrimal duct opens below the anterior part of the inferior concha. The inferior, middle, and superior nasal meatus are located below their respective concha. The superior meatus is located between the middle and superior concha. The sphenoethmoidal recess, a narrow cleft located above the superior concha, separates the superior concha from the anterior surface of the sphenoid sinus and is the site of the ostium communicating the sphenoid sinus and nasal cavity. The eustachian tube opens into the nasopharynx in front of Rosenmüller’s fossa. D, The concha has been removed. The maxillary and frontal sinuses drain into the middle meatus. The lacrimal duct opens below the inferior turbinate into the inferior meatus. The ethmoid bullae are rounded prominences overlying the middle ethmoid air cells. The anterior ethmoid air cells drain into the superior meatus. The posterior ethmoid air cells and the sphenoid sinus drain into the sphenoethmoidal recess. E, Enlarged view after removal of the nasal mucosa. The olfactory fila pass through the small openings in the cribriform plate to innervate the olfactory mucosa. The sphenopalatine artery, the terminal branch of the maxillary artery, passes through the sphenopalatine foramen in the medial wall of the pterygopalatine fossa and gives rise to the posterior lateral nasal arteries. F, The cribriform plate and medial wall of the ethmoid air cells have been removed. The thin lateral wall of the ethmoidal and sphenoid sinuses forms the medial wall of the orbit. The frontal sinus opens into the anterior part of the middle meatus. (Images courtesy of AL Rhoton, Jr.)