Sphenoidal 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	D013101
TA	A06.1.03.003
FMA	54683
	Anatomical terms of bone [ edit on Wikidata]

Last updated March 06, 2019

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.^[1]

The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the temporal bone and the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly or bat with its wings extended.

In biology, a septum is a wall, dividing a cavity or structure into smaller ones.

Structure

Paranasal sinuses Paranasal Sinuses lat.jpg — Paranasal sinuses

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

The basilar part of the occipital bone extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline.

Occipital bone saucer-shaped membrane bone situated at the back and lower part of the cranium

The occipital bone is a cranial dermal bone and the main bone of the occiput. It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cerebrum. At the base of skull in the occipital bone, there is a large oval opening called the foramen magnum, which allows the passage of the spinal cord.

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.^[2]

The sphenoethmoidal recess is a small space in the nasal cavity into which the sphenoidal sinus and posterior ethmoid sinus open. It lies posterior and superior to the superior concha.

The choana, posterior nasal aperture or internal nostril is one of two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods with secondary palates, including humans and other mammals.

Development

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.^[2]

Nerve supply

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 controls secretion of mucus.

The posterior ethmoidal nerve is a branch of the nasociliary nerve.

The ophthalmic nerve is the first branch of the trigeminal nerve. The ophthalmic nerve is a sensory nerve mostly carrying general somatic afferent fibers that transmit sensory information to the CNS from structures of the eyeball, the skin of the upper face and anterior scalp, the lining of the upper part of the nasal cavity and air cells, and the meninges of the anterior cranial fossa. Some of ophthalmic nerve branches also convey parasympathetic fibers.

The facial nerve is the seventh cranial nerve, or simply CN VII. It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerves typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI and anterior to cranial nerve VIII.

Clinical significance

A potential complication of sphenoidal sinusitis is cavernous sinus thrombosis.
If a fast-growing tumor erodes the floor of the sinus, the vidian nerve could be in danger.

Cavernous sinus thrombosis Human disease

Cavernous sinus thrombosis (CST) is the formation of a blood clot within the cavernous sinus, a cavity at the base of the brain which drains deoxygenated blood from the brain back to the heart. This is a rare disorder and can be of two types–septic cavernous thrombosis and aseptic cavernous thrombosis. Most commonly the form is of septic cavernous sinus thrombosis. The cause is usually from a spreading infection in the nose, sinuses, ears, or teeth. Staphylococcus aureus and Streptococcus are often the associated bacteria.

If the tumor spreads laterally, the cavernous sinus and all its constituent nerves could be in danger. An endonasal surgical procedure called a sphenoidotomy may be carried out to enlarge the sphenoid sinus, usually in order to drain it.^[3]

Use in neurosurgery

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.

Related Research Articles

Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoidal sinuses are behind the eyes. The sinuses are named for the facial bones in which they are located.

The ethmoid bone is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that make up the orbit of the eye.

The palatine bones are two irregular bones of the facial skeleton in many animal species. Together with the maxillae they comprise the hard palate.

The internal carotid artery is a major paired artery, one on each side of the head and neck, in human anatomy. They arise from the common carotid arteries where these bifurcate into the internal and external carotid arteries at cervical vertebral level 3 or 4; the internal carotid artery supplies the brain, while the external carotid nourishes other portions of the head, such as face, scalp, skull, and meninges.

The sella turcica is a saddle-shaped depression in the body of the sphenoid bone of the human skull and of the skulls of other hominids including chimpanzees, orangutans, and gorillas. It serves as a cephalometric landmark. The pituitary gland or hypophysis is located within the most inferior aspect of the sella turcica, the hypophyseal fossa.

The pyramid-shaped maxillary sinus is the largest of the paranasal sinuses, and drains into the middle meatus of the nose.

The ethmoid sinuses or ethmoidal air cells of the ethmoid bone are one of the four paired paranasal sinuses. The cells are variable in both size and number in the lateral mass of each of the ethmoid bones and cannot be palpated during an extraoral examination. They are divided into anterior and posterior groups. The ethmoidal air cells are numerous thin-walled cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla, lacrimal, sphenoidal, and palatine bones. They lie between the upper parts of the nasal cavities and the orbits, and are separated from these cavities by thin bony lamellae.

The maxillary nerve (CN V₂) is one of the three branches or divisions of the trigeminal nerve, the fifth (V) cranial nerve. It comprises the principal functions of sensation from the maxillary, nasal cavity, sinuses, the palate and subsequently that of the mid-face, and is intermediate, both in position and size, between the ophthalmic nerve and the mandibular nerve.

The sphenoidal conchae are two thin, curved plates, situated at the anterior and lower part of the body of the sphenoid. An aperture of variable size exists in the anterior wall of each, and through this the sphenoidal sinus opens into the nasal cavity.

The pterygoid processes of the sphenoid, one on either side, descend perpendicularly from the regions where the body and the greater wings of the sphenoid bone unite.

The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone; there is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward.

The sphenopalatine foramen is a foramen in the skull that connects the nasal cavity with the pterygopalatine fossa.

The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest.

The anterior cranial fossa is a depression in the floor of the cranial base which houses the projecting frontal lobes of the brain. It is formed by the orbital plates of the frontal, the cribriform plate of the ethmoid, and the small wings and front part of the body of the sphenoid; it is limited behind by the posterior borders of the small wings of the sphenoid and by the anterior margin of the chiasmatic groove. The lesser wings of the sphenoid separate the anterior and middle fossae.

The perpendicular plate of palatine bone is the vertical part of the palatine bone, and is thin, of an oblong form, and presents two surfaces and four borders.

The body of the sphenoid bone, more or less cubical in shape, is hollowed out in its interior to form two large cavities, the sphenoidal sinuses, which are separated from each other by a septum.

Endoscopic endonasal surgery is a minimally invasive technique used mainly in neurosurgery and otolaryngology. A neurosurgeon or an otolaryngologist, using an endoscope that is entered through the nose, fixes or removes brain defects or tumors in the anterior skull base. Normally an otolaryngologist performs the initial stage of surgery through the nasal cavity and sphenoid bone; a neurosurgeon performs the rest of the surgery involving drilling into any cavities containing a neural organ such as the pituitary gland.

References

This article incorporates text in the public domain from page 998 of the 20th edition of Gray's Anatomy (1918)

↑ Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 64
1 2 Human Anatomy, Jacob, Elsevier, 2008, page 211
↑ Kozłowski, Z; Mazerant, M; Skóra, W; Dabrowska, K (2008). "[Sphenoidotomy--the treatment of patients with isolated sphenoid sinus diseases]". Otolaryngologia polska = The Polish otolaryngology. 62 (5): 582–6. doi:10.1016/S0030-6657(08)70319-6. PMID 19004262.

External links

Anatomy photo:33:st-0712 at the SUNY Downstate Medical Center
lesson9 at The Anatomy Lesson by Wesley Norman (Georgetown University) ( latnasalwall3 )

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[1] Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 64

[:0-2] 1 2 Human Anatomy, Jacob, Elsevier, 2008, page 211

[Kozlowski-3] Kozłowski, Z; Mazerant, M; Skóra, W; Dabrowska, K (2008). "[Sphenoidotomy--the treatment of patients with isolated sphenoid sinus diseases]". Otolaryngologia polska = The Polish otolaryngology. 62 (5): 582–6. doi:10.1016/S0030-6657(08)70319-6. PMID 19004262.