Body of sphenoid bone
Encyclopedia
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 air sinuses, which are separated from each other by a septum
.
, for articulation with the cribriform plate
of the ethmoid bone
; behind this is a smooth surface slightly raised in the middle line, and grooved on either side for the olfactory lobes of the brain
.
This surface is bounded behind by a ridge, which forms the anterior border of a narrow, transverse groove, the prechiasmatic groove, above and behind which lies the optic chiasma; the groove ends on either side in the optic foramen
, which transmits the optic nerve
and ophthalmic artery
into the orbital cavity.
Behind the chiasmatic groove is an elevation, the tuberculum sellae
; and still more posteriorly, a deep depression, the sella turcica
(the Turkish saddle), the deepest part of which lodges the pituitary gland
and is known as the hypophyseal fossa.
The anterior boundary of the sella turcica
is completed by two small eminences, one on either side, called the middle clinoid processes, while the posterior boundary is formed by a square-shaped plate of bone, the dorsum sellae
, ending at its superior angles in two tubercles, the posterior clinoid processes, the size and form of which vary considerably in different individuals.
The posterior clinoid processes deepen the sella turcica, and give attachment to the tentorium cerebelli
.
On either side of the dorsum sellae is a notch for the passage of the abducent nerve
, and below the notch a sharp process, the petrosal process, which articulates with the apex of the petrous portion of the temporal bone
, and forms the medial boundary of the foramen lacerum
.
Behind the dorsum sellae is a shallow depression, the clivus
, which slopes obliquely backward, and is continuous with the groove on the basilar portion of the occipital bone
; it supports the upper part of the pons
.
s.
Above the attachment of each greater wing is a broad groove, curved something like the italic letter f; it lodges the internal carotid artery
and the cavernous sinus
, and is named the carotid sulcus.
Along the posterior part of the lateral margin of this groove, in the angle between the body and greater wing, is a ridge of bone, called the sphenoidal lingula.
Between the eighteenth and twenty-fifth years this becomes ossified, ossification commencing above and extending downward.
.
On either side of the crest is an irregular opening leading into the corresponding sphenoidal air sinus.
These sinuses are two large, irregular cavities hollowed out of the interior of the body of the bone, and separated from one another by a bony septum
, which is commonly bent to one or the other side.
They vary considerably in form and size, are seldom symmetrical, and are often partially subdivided by irregular bony laminae.
Occasionally, they extend into the basilar part of the occipital bone
nearly as far as the foramen magnum. They begin to be developed before birth, and are of a considerable size by the age of six.
They are partially closed, in front and below, by two thin, curved plates of bone, the sphenoidal conchae
, leaving in the articulated skull a round opening at the upper part of each sinus by which it communicates with the upper and back part of the nasal cavity and occasionally with the posterior ethmoidal air cells.
The lateral margin of the anterior surface is serrated, and articulates with the lamina papyracea of the ethmoid, completing the posterior ethmoidal cells; the lower margin articulates with the orbital process of the palatine bone, and the upper with the orbital plate of the frontal bone.
On either side of the rostrum is a projecting lamina, the vaginal process, directed medialward from the base of the medial pterygoid plate
, with which it will be described.
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...
, more or less cubical in shape, is hollowed out in its interior to form two large cavities, the sphenoidal air sinuses, which are separated from each other by a septum
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
.
Superior surface
The superior surface of the body [Fig. 1] presents in front a prominent spine, the ethmoidal spineEthmoidal spine
The superior surface of the body of the sphenoid bone presents in front a prominent spine, the ethmoidal spine, for articulation with the cribriform plate of the ethmoid; behind this is a smooth surface slightly raised in the middle line, and grooved on either side for the olfactory lobes of the...
, for articulation with the cribriform plate
Cribriform plate
The cribriform plate of the ethmoid bone is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities....
of the ethmoid bone
Ethmoid bone
The ethmoid bone is a bone in the skull that separates the nasal cavity from the brain. As such, 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 makes up the orbit of the eye...
; behind this is a smooth surface slightly raised in the middle line, and grooved on either side for the olfactory lobes of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
.
This surface is bounded behind by a ridge, which forms the anterior border of a narrow, transverse groove, the prechiasmatic groove, above and behind which lies the optic chiasma; the groove ends on either side in the optic foramen
Optic foramen
The optic foramen is the opening to the optic canal.The superior surface of the sphenoid bone is bounded behind by a ridge, which forms the anterior border of a narrow, transverse groove, the chiasmatic groove , above and behind which lies the optic chiasma; the groove ends on either side in the...
, which transmits the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
and ophthalmic artery
Ophthalmic artery
The ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges...
into the orbital cavity.
Behind the chiasmatic groove is an elevation, the tuberculum sellae
Tuberculum sellae
In the sphenoid bone, behind the chiasmatic groove is an elevation, the tuberculum sellæ .-External links:*...
; and still more posteriorly, a deep depression, the sella turcica
Sella turcica
-External links:*...
(the Turkish saddle), the deepest part of which lodges 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...
and is known as the hypophyseal fossa.
The anterior boundary of the sella turcica
Sella turcica
-External links:*...
is completed by two small eminences, one on either side, called the middle clinoid processes, while the posterior boundary is formed by a square-shaped plate of bone, the dorsum sellae
Dorsum sellae
In the sphenoid bone, the anterior boundary of the sella turcica is completed by two small eminences, one on either side, called the middle clinoid processes, while the posterior boundary is formed by a square-shaped plate of bone, the dorsum sellæ, ending at its superior angles in two tubercles,...
, ending at its superior angles in two tubercles, the posterior clinoid processes, the size and form of which vary considerably in different individuals.
The posterior clinoid processes deepen the sella turcica, and give attachment to the tentorium cerebelli
Tentorium cerebelli
The tentorium cerebelli or cerebellar tentorium is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes.-Anatomy:...
.
On either side of the dorsum sellae is a notch for the passage of the abducent nerve
Abducent nerve
The abducens nerve or abducent nerve is a somatic efferent nerve that controls the movement of a single muscle, the lateral rectus muscle of the eye, in humans. In most other mammals it also innervates the musculus retractor bulbi, which can retract the eye for protection...
, and below the notch a sharp process, the petrosal process, which articulates with the apex of the petrous portion of the temporal bone
Temporal bone
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebrum.The temporal bone supports that part of the face known as the temple.-Parts:The temporal bone consists of four parts:* Squama temporalis...
, and forms the medial boundary of the foramen lacerum
Foramen lacerum
The foramen lacerum is a triangular hole in the base of the skull located at the base of the medial pterygoid plate.-Transit through the foramen lacerum:...
.
Behind the dorsum sellae is a shallow depression, the clivus
Clivus (anatomy)
The clivus is a part of the cranium, a shallow depression behind the dorsum sellæ that slopes obliquely backward. It forms a gradual sloping process at the anterior most portion of the basilar occipital bone at its junction with the sphenoid bone. On axial planes, it sits just posterior to the...
, which slopes obliquely backward, and is continuous with the groove on the basilar portion of the occipital bone
Occipital 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...
; it supports the upper part of the pons
Pons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
.
Lateral surfaces
The lateral surfaces of the body are united with the greater wings of the sphenoid and the medial pterygoid plateMedial pterygoid plate
The medial pterygoid plate of the sphenoid is narrower and longer than the lateral pterygoid plate; it curves lateralward at its lower extremity into a hook-like process, the pterygoid hamulus, around which the tendon of the Tensor veli palatini glides.The lateral surface of this plate forms part...
s.
Above the attachment of each greater wing is a broad groove, curved something like the italic letter f; it lodges the internal carotid artery
Internal carotid artery
In human anatomy, the internal carotid arteries are two major arteries, one on each side of the head and neck. They arise from the common carotid arteries where these bifurcate into the internal and external carotid artery, and they supply the brain....
and 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 is named the carotid sulcus.
Along the posterior part of the lateral margin of this groove, in the angle between the body and greater wing, is a ridge of bone, called the sphenoidal lingula.
Posterior surfaces
The posterior surface, quadrilateral in form [Fig. 3], is joined, during infancy and adolescence, to the basilar part of the occipital bone by a plate of cartilage.Between the eighteenth and twenty-fifth years this becomes ossified, ossification commencing above and extending downward.
Anterior surface
The anterior surface of the body [Fig. 2] presents, in the middle line, a vertical crest, the sphenoidal crest, which articulates with the perpendicular plate of the ethmoid, and forms part of the nasal septumNasal septum
The nasal septum separates the left and right airways in the nose, dividing the two nostrils.It is depressed by the Depressor septi nasi muscle.-Composition:The fleshy external end of the nasal septum is sometimes also called columella....
.
On either side of the crest is an irregular opening leading into the corresponding sphenoidal air sinus.
These sinuses are two large, irregular cavities hollowed out of the interior of the body of the bone, and separated from one another by a bony septum
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
, which is commonly bent to one or the other side.
They vary considerably in form and size, are seldom symmetrical, and are often partially subdivided by irregular bony laminae.
Occasionally, they extend into the basilar part of the occipital bone
Occipital 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...
nearly as far as the foramen magnum. They begin to be developed before birth, and are of a considerable size by the age of six.
They are partially closed, in front and below, by two thin, curved plates of bone, the sphenoidal conchae
Sphenoidal conchae
The sphenoidal conchae are two thin, curved plates, situated at the anterior and lower part of the body of the sphenoid...
, leaving in the articulated skull a round opening at the upper part of each sinus by which it communicates with the upper and back part of the nasal cavity and occasionally with the posterior ethmoidal air cells.
The lateral margin of the anterior surface is serrated, and articulates with the lamina papyracea of the ethmoid, completing the posterior ethmoidal cells; the lower margin articulates with the orbital process of the palatine bone, and the upper with the orbital plate of the frontal bone.
Inferior surface
The inferior surface presents, in the middle line, a triangular spine, the sphenoidal rostrum, which is continuous with the sphenoidal crest on the anterior surface, and is received in a deep fissure between the alæ of the vomer.On either side of the rostrum is a projecting lamina, the vaginal process, directed medialward from the base of the medial pterygoid plate
Medial pterygoid plate
The medial pterygoid plate of the sphenoid is narrower and longer than the lateral pterygoid plate; it curves lateralward at its lower extremity into a hook-like process, the pterygoid hamulus, around which the tendon of the Tensor veli palatini glides.The lateral surface of this plate forms part...
, with which it will be described.