Sphenoidal sinus
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.
Relations
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.
Development
They are present as very small cavities at birth, but their main development takes place after puberty.
Innervation
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.
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