Sphenoidal sinuses
Encyclopedia
The two sphenoidal sinuses (or sphenoid) contained within the body of the sphenoid
vary in size and shape; owing to the lateral displacement of the intervening septum
they are rarely symmetrical.
The following are their average measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior depth, 2.2 cm.
.
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.
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.
If a fast-growing tumor erodes the floor of the sinus, the vidian nerve could be in danger.
If the tumor spreads laterally, the cavernous sinus
and all its constituent nerves could be in danger.
s, and postganglionic parasympathetic fibers of the facial nerve
that synapse
d at the pterygopalatine ganglion
which control secretion
of mucous
.
.
Sphenoid bone
The sphenoid bone is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit...
vary in size and shape; owing to the lateral displacement of the intervening septum
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
they are rarely symmetrical.
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 boneOccipital bone
The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the cranium, is trapezoidal in shape and curved on itself...
.
Each sinus opens into the roof of the nasal cavity via apertures on the posterior wall of the sphenoethmoidal recess
Sphenoethmoidal recess
The sphenoethmoidal recessis a small space posterior and superior to the superior concha into which the sphenoidal sinus opens.-External links: - "The turbinates have been cut and removed to illustrate the meatus and openings into them."...
directly above the choana
Choana
Choana is the posterior nasal aperture.The choanae are separated by the vomer.- Boundaries :It is the opening between the nasal cavity and the nasopharynx....
. The apertures are located high on the anterior walls of the sinuses themselves.
Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland
Pituitary gland
In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...
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.
If a fast-growing tumor erodes the floor of the sinus, the vidian nerve could be in danger.
If the tumor spreads laterally, the cavernous sinus
Cavernous sinus
The cavernous sinus , within the human head, is a large collection of thin-walled veins creating a cavity bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica.-Contents:...
and all its constituent nerves could be in danger.
Innervation
The mucous membrane receives sensory innervation by the posterior ethmoidal nervePosterior ethmoidal nerve
The posterior ethmoidal nerve is a branch of the nasociliary nerve.It passes through the posterior ethmoidal foramen, with the posterior ethmoidal artery.It carries sensory information from the sphenoid sinus and posterior ethmoidal air cells....
s, and postganglionic parasympathetic fibers of the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
that synapse
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
d at the pterygopalatine ganglion
Pterygopalatine ganglion
The pterygopalatine ganglion is a parasympathetic ganglion found in the pterygopalatine fossa. It is one of four parasympathetic ganglia of the head and neck....
which control secretion
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...
of mucous
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
.
Development
They are present as minute cavities at birth, but their main development takes place after pubertyPuberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
.