Sphenoid sinus

Sphenoidal sinuses
Lateral wall of nasal cavity; the three nasal conchæ have been removed. (Sphenoidal sinus visible at upper right, in dark circle.)
Nose and nasal cavities. (Sphenoid sinus labeled at upper right.)
Details
Nerve	posterior ethmoidal nerves, and orbital branches of the pterygopalatine ganglion
Identifiers
Latin	sinus sphenoidalis
MeSH	A04.531.621.827
TA	A06.1.03.003
FMA	54683
Anatomical terms of bone []

Each of the paired sphenoidal sinuses (components of the paranasal sinuses) is contained within the body of the sphenoid. They vary in size and shape and owing to the lateral displacement of the intervening septum they are rarely symmetrical. They cannot be palpated during an extraoral examination.

The following are their average measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior depth, 2.2 cm.

When exceptionally large they may extend into the roots of the pterygoid processes or great wings, and may invade the basilar part of the occipital bone.

Each sinus opens into the roof of the nasal cavity via apertures on the posterior wall of the sphenoethmoidal recess directly above the choana. The apertures are located high on the anterior walls of the sinuses themselves.

They are present as very small cavities at birth, and slowly develop with the growth of the skull. Just after puberty the sinuses finish development.

The mucous membrane receives sensory innervation by the posterior ethmoidal nerves (branch of the ophthalmic nerve), and postganglionic parasympathetic fibers of the facial nerve that synapsed at the pterygopalatine ganglion which control secretion of mucus.

If the tumor spreads laterally, the cavernous sinus and all its constituent nerves could be in danger.

Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland can be surgically approached through the roof of the nasal cavities by first passing through the anterioinferior aspect of the sphenoid bone and into the sinuses, followed by entry through the top of the sphenoid bone into the hypophyseal fossa.