The sphenoid sinus is a paired paranasal sinus occurring within the within the body of the sphenoid bone. It represents one pair of the four paired

paranasal sinus 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 spheno ...

es.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 64 The pair of sphenoid sinuses are separated in the middle by a septum of sphenoid sinuses. Each sphenoid sinus communicates with the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal ...

via the opening of sphenoidal sinus. The two sphenoid sinuses vary in size and shape, and are usually asymmetrical.

Anatomy

On average, a sphenoid sinus measures 2.2 cm vertical height, 2 cm in transverse breadth; and 2.2 cm antero-posterior depth. Each spehoid sinus is contained within the

body of sphenoid bone 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. Superior surface The superior surface of the bo ...

, being situated just inferior to the

sella turcica The sella turcica (Latin for 'Turkish saddle') 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, gorillas and orangutans. It serves as a cephalometric ...

. The two sphenoid sinuses are separated medially by the septum of sphenoidal sinuses (which is usually asymmetrical). An opening of sphenoidal sinus forms a passage between each sphenoidal sinus, and the

. Posteriorly, an opening of sphenoidal sinus opens into the sphenoidal sinus by an aperture high on the anterior wall the sinus; anteriorly, an opening of sphenoidal sinus opens into the roof of the

via an aperture on the posterior wall of the

sphenoethmoidal recess 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 superior nasal concha is a small, curved plate of bone r ...

(occurring just superior the

choana The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodilia ...

).Human Anatomy, Jacob, Elsevier, 2008, page 211

Innervation

The mucous membrane receives sensory innervation by the posterior ethmoidal nerves (branch of the

ophthalmic nerve The ophthalmic nerve (V1) is a sensory nerve of the face. It is one of three divisions of the trigeminal nerve (CN V). It has three branches that provide sensory innervation to the eye, the skin of the upper face, and the skin of the anterior scal ...

), and

postganglionic In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers. Neurotransmitters The neurotransmitters of postganglionic fibers differ: * In the parasympathetic division, neurons are ''ch ...

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part o ...

fibers of the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of ta ...

that

synapse In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses fr ...

d at the

pterygopalatine ganglion The pterygopalatine ganglion (aka Meckel's ganglion, nasal ganglion, or sphenopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa. It is largely innervated by the greater petrosal nerve (a branch of the facial n ...

which controls

secretion 440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classica ...

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...

Anatomical relations

Proximal structures include: the optic canal and

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

, internal carotid artery,

cavernous sinus The cavernous sinus within the human head is one of the dural venous sinuses creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica. Structure The c ...

trigeminal nerve In neuroanatomy, the trigeminal nerve (literal translation, lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for Sense, sensation in the face and motor functions ...

pituitary gland In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The hypop ...

, and the anterior ethmoidal cells.

Anatomical variation

The sphenoid sinuses vary in size and shape, and, owing to the lateral displacement of the intervening

septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interat ...

of sphenoid sinuses, are rarely symmetrical. When exceptionally large, the sphenoid sinuses may extend into the roots of the pterygoid processes or greater wings of sphenoid bone, and may invade the basilar part of the

occipital bone The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the c ...

. The septum of the sphenoidal sinuses may be partially or completely absent. Additional incomplete septa may also be present.

Development

The sphenoidal sinuses are minute at birth; their main development takes place after puberty.

Clinical significance

The spehnoid sinuses cannot be palpated during an extraoral examination. A potential complication of sphenoidal sinusitis is cavernous sinus thrombosis. If a fast-growing tumor erodes the floor of the sphenoidal sinus, the vidian nerve could be in danger. If the tumor spreads laterally, the

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.

Transsphenoidal surgery

Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and

hypophyseal fossa The sella turcica ( Latin for 'Turkish saddle') 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, gorillas and orangutans. It serves as a cephalome ...

above, the

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

References

External links

* * () {{Authority control Bones of the head and neck