Middle cranial fossa
Encyclopedia
The middle 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.
It is bounded in front by the posterior margins of the lesser wings of the sphenoid bone
, the anterior clinoid processes, and the ridge forming the anterior margin of the chiasmatic groove
; behind, by the superior angles of the petrous portions of the temporal bones and the dorsum sellæ; laterally by the temporal squamæ, sphenoidal angles of the parietals, and greater wings of the sphenoid. It is traversed by the squamosal, sphenoparietal, sphenosquamosal, and sphenopetrosal sutures.
It houses the temporal lobes of the brain.
and tuberculum sellæ; the chiasmatic groove ends on either side at the optic foramen
, which transmits the optic nerve
and ophthalmic artery
to the orbital cavity.
Behind the optic foramen the anterior clinoid process
is directed backward and medialward and gives attachment to the tentorium cerebelli
.
Behind the tuberculum sellæ is a deep depression, the sella turcica
, containing the fossa hypophyseos
, which lodges the hypophysis
, and presents on its anterior wall the middle clinoid processes.
The sella turcica
is bounded posteriorly by a quadrilateral plate of bone, the dorsum sellæ, the upper angles of which are surmounted by the posterior clinoid processes: these afford attachment to the tentorium cerebelli, and below each is a notch for the abducent nerve
.
On either side of the sella turcica is the carotid groove
, which is broad, shallow, and curved somewhat like the italic letter f.
It begins behind at the foramen lacerum
, and ends on the medial side of the anterior clinoid process, where it is sometimes converted into a foramen (carotico-clinoid) by the union of the anterior with the middle clinoid process; posteriorly, it is bounded laterally by the lingula
.
This groove lodges the cavernous sinus
and the internal carotid artery
, the latter being surrounded by a plexus of sympathetic nerves.
.
They are marked by depressions for the brain convolutions and traversed by furrows for the anterior and posterior branches of the middle meningeal vessels.
These furrows begin near the foramen spinosum
, and the anterior runs forward and upward to the sphenoidal angle of the parietal, where it is sometimes converted into a bony canal; the posterior runs lateralward and backward across the temporal squama and passes on to the parietal near the middle of its lower border.
The following apertures are also to be seen.
In front is the superior orbital fissure, bounded above by the small wing, below, by the great wing, and medially, by the body of the sphenoid
; it is usually completed laterally by the orbital plate
of the frontal bone
.
It transmits to the orbital cavity the oculomotor, the trochlear, the ophthalmic division of the trigeminal, and the abducent nerves, some filaments from the cavernous plexus
of the sympathetic, and the orbital branch of the middle meningeal artery
; and from the orbital cavity a recurrent branch from the lacrimal artery
to the dura mater
, and the ophthalmic veins
.
Behind the medial end of the superior orbital fissure is the foramen rotundum
, for the passage of the maxillary nerve.
Behind and lateral to the foramen rotundum is the foramen ovale
, which transmits the mandibular nerve
, the accessory meningeal artery, and the lesser superficial petrosal nerve.
Medial to the foramen ovale is the foramen Vesalii, which varies in size in different individuals, and is often absent; when present, it opens below at the lateral side of the scaphoid fossa
, and transmits a small vein.
Lateral to the foramen ovale is the foramen spinosum
, for the passage of the middle meningeal vessels, and a recurrent branch from the mandibular nerve.
Medial to the foramen ovale is the foramen lacerum
; in the fresh state the lower part of this aperture is filled up by a layer of fibrocartilage
, while its upper and inner parts transmit the internal carotid artery
surrounded by a plexus of sympathetic nerves.
The nerve of the pterygoid canal
and a meningeal branch from the ascending pharyngeal artery
pierce the layer of fibrocartilage.
On the anterior surface of the petrous portion of the temporal bone are seen the eminence caused by the projection of the superior semicircular canal
; in front of and a little lateral to this a depression corresponding to the roof of the tympanic cavity
; the groove leading to the hiatus of the facial canal
, for the transmission of the greater superficial petrosal nerve and the petrosal branch of the middle meningeal artery
; beneath it, the smaller groove, for the passage of the lesser superficial petrosal nerve; and, near the apex of the bone, the depression for the semilunar ganglion and the orifice of the carotid canal.
Anterior cranial fossa
The floor of the anterior fossa 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...
, is narrow medially and widens laterally to the sides of the skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
. It is separated from the posterior fossa
Posterior cranial fossa
The posterior cranial fossa is part of the intracranial cavity, located between the foramen magnum and tentorium cerebelli. It contains the brainstem and cerebellum.This is the most inferior of the fossae. It houses the cerebellum, medulla and pons....
by 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...
and the petrous crest.
It is bounded in front by the posterior margins of the lesser wings of the sphenoid bone
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...
, the anterior clinoid processes, and the ridge forming the anterior margin of the chiasmatic groove
Chiasmatic groove
The superior surface of the body 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 of cranial nerve 2 .The groove ends on either side in the optic foramen, which...
; behind, by the superior angles of the petrous portions of the temporal bones and the dorsum sellæ; laterally by the temporal squamæ, sphenoidal angles of the parietals, and greater wings of the sphenoid. It is traversed by the squamosal, sphenoparietal, sphenosquamosal, and sphenopetrosal sutures.
It houses the temporal lobes of the brain.
Middle part
The middle part of the fossa presents, in front, the chiasmatic grooveChiasmatic groove
The superior surface of the body 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 of cranial nerve 2 .The groove ends on either side in the optic foramen, which...
and tuberculum sellæ; the chiasmatic groove ends on either side at 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...
to the orbital cavity.
Behind the optic foramen the anterior clinoid process
Anterior clinoid process
In the sphenoid bone, the posterior border, smooth and rounded, is received into the lateral fissure of the brain; the medial end of this border forms the anterior clinoid process, which gives attachment to the tentorium cerebelli; it is sometimes joined to the middle clinoid process by a spicule...
is directed backward and medialward and gives 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:...
.
Behind the tuberculum sellæ is a deep depression, the sella turcica
Sella turcica
-External links:*...
, containing the fossa hypophyseos
Fossa hypophyseos
In the sphenoid bone, behind the chiasmatic groove is an elevation, the tuberculum sellae; and still more posteriorly, a deep depression, the sella turcica, the deepest part of which lodges the hypophysis cerebri and is known as the fossa hypophyseos .-External links:* - "Cranial Fossae:...
, which lodges the hypophysis
Hypophysis
Hypophysis may refer to:*Pituitary gland*Hypophysis...
, and presents on its anterior wall the middle clinoid processes.
The sella turcica
Sella turcica
-External links:*...
is bounded posteriorly by a quadrilateral plate of bone, the dorsum sellæ, the upper angles of which are surmounted by the posterior clinoid processes: these afford attachment to the tentorium cerebelli, and below each is a notch for 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...
.
On either side of the sella turcica is the carotid groove
Carotid groove
Above the attachment of each great wing of the sphenoid bone 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 groove....
, which is broad, shallow, and curved somewhat like the italic letter f.
It begins behind at 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:...
, and ends on the medial side of the anterior clinoid process, where it is sometimes converted into a foramen (carotico-clinoid) by the union of the anterior with the middle clinoid process; posteriorly, it is bounded laterally by the lingula
Lingula
Lingula is Latin for "little tongue". It can stand for:* Lingula , a brachiopod genus of the family Lingulidae, which is among the few brachiopods surviving today but also known from fossils over 500 million years old* In anatomy:...
.
This groove lodges 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 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....
, the latter being surrounded by a plexus of sympathetic nerves.
Lateral parts
The lateral parts of the middle fossa are of considerable depth, and support the temporal lobes of the brainBrain
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,...
.
They are marked by depressions for the brain convolutions and traversed by furrows for the anterior and posterior branches of the middle meningeal vessels.
These furrows begin near the foramen spinosum
Foramen spinosum
The foramen spinosum is one of several foramina located in the base of the skull, on the sphenoid bone, situated lateral to the foramen ovale, in a posterior angle.-Contents:It permits the passage of certain arteries, veins and/or other structures:...
, and the anterior runs forward and upward to the sphenoidal angle of the parietal, where it is sometimes converted into a bony canal; the posterior runs lateralward and backward across the temporal squama and passes on to the parietal near the middle of its lower border.
The following apertures are also to be seen.
In front is the superior orbital fissure, bounded above by the small wing, below, by the great wing, and medially, by the body of the sphenoid
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...
; it is usually completed laterally by the orbital plate
Orbital plate
Orbital plate can refer to:* Orbital part of frontal bone* Orbital lamina of ethmoid bone...
of the frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
.
It transmits to the orbital cavity the oculomotor, the trochlear, the ophthalmic division of the trigeminal, and the abducent nerves, some filaments from the cavernous plexus
Cavernous plexus
The cavernous nerve plexus is situated below and medial to that part of the internal carotid artery which is placed by the side of the sella turcica in the cavernous sinus, and is formed chiefly by the medial division of the internal carotid nerve....
of the sympathetic, and the orbital branch of the middle meningeal artery
Middle meningeal artery
The middle meningeal artery is typically the third branch of the first part of the maxillary artery, one of the two terminal branches of the external carotid artery...
; and from the orbital cavity a recurrent branch from the lacrimal artery
Lacrimal artery
The lacrimal artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic artery: not infrequently it is given off before the artery enters the orbit....
to the dura mater
Dura mater
The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
, and the ophthalmic veins
Ophthalmic veins
Ophthalmic veins are veins which drain the eye.More specifically, they can refer to:* Superior ophthalmic vein* Inferior ophthalmic vein...
.
Behind the medial end of the superior orbital fissure is the foramen rotundum
Foramen rotundum
The foramen rotundum is a circular hole in the sphenoid bone that connects the middle cranial fossa and the pterygopalatine fossa.-Structure:...
, for the passage of the maxillary nerve.
Behind and lateral to the foramen rotundum is the foramen ovale
Foramen ovale
There are multiple structures in the human body with the name foramen ovale :* In the fetal heart, the foramen ovale is a shunt from the right atrium to left atrium....
, which transmits the mandibular nerve
Mandibular nerve
The mandibular nerve is the largest of the three branches of the trigeminal nerve.-Roots:It is made up of two roots:* a large sensory root proceeding from the inferior angle of the trigeminal ganglion....
, the accessory meningeal artery, and the lesser superficial petrosal nerve.
Medial to the foramen ovale is the foramen Vesalii, which varies in size in different individuals, and is often absent; when present, it opens below at the lateral side of the scaphoid fossa
Scaphoid fossa
In the pterygoid processes of the sphenoid, above the pterygoid fossa is a small, oval, shallow depression, the scaphoid fossa, which gives origin to the Tensor veli palatini.-External links:*...
, and transmits a small vein.
Lateral to the foramen ovale is the foramen spinosum
Foramen spinosum
The foramen spinosum is one of several foramina located in the base of the skull, on the sphenoid bone, situated lateral to the foramen ovale, in a posterior angle.-Contents:It permits the passage of certain arteries, veins and/or other structures:...
, for the passage of the middle meningeal vessels, and a recurrent branch from the mandibular nerve.
Medial to the foramen ovale is 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:...
; in the fresh state the lower part of this aperture is filled up by a layer of fibrocartilage
Fibrocartilage
White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions. It owes its flexibility and toughness to the former of these constituents, and its elasticity to the latter...
, while its upper and inner parts transmit 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....
surrounded by a plexus of sympathetic nerves.
The nerve of the pterygoid canal
Pterygoid canal
The pterygoid canal is a passage in the skull leading from just anterior to the foramen lacerum in the middle cranial fossa to the pterygopalatine fossa.-Structure:...
and a meningeal branch from the ascending pharyngeal artery
Ascending pharyngeal artery
The ascending pharyngeal artery, the smallest branch of the external carotid, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the Stylopharyngeus...
pierce the layer of fibrocartilage.
On the anterior surface of the petrous portion of the temporal bone are seen the eminence caused by the projection of the superior semicircular canal
Superior semicircular canal
The superior semicircular canal is a part of the vestibular system and detects rotation of the head around a rostral-caudal axis.-Structure:...
; in front of and a little lateral to this a depression corresponding to the roof of the tympanic cavity
Tympanic cavity
The tympanic cavity is a small cavity surrounding the bones of the middle ear.It is formed from the tubotympanic recess, an expansion of the first pharyngeal pouch....
; the groove leading to the hiatus of the facial canal
Facial canal
The facial canal is a Z-shaped canal running through the temporal bone from the internal acoustic meatus to the stylomastoid foramen. In humans it is approximately 3 centimeters long, which makes it the longest human osseous canal of a nerve...
, for the transmission of the greater superficial petrosal nerve and the petrosal branch of the middle meningeal artery
Middle meningeal artery
The middle meningeal artery is typically the third branch of the first part of the maxillary artery, one of the two terminal branches of the external carotid artery...
; beneath it, the smaller groove, for the passage of the lesser superficial petrosal nerve; and, near the apex of the bone, the depression for the semilunar ganglion and the orifice of the carotid canal.