Anterior cranial fossa
Encyclopedia
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 chiasmatic groove
. The lesser wings of the sphenoid separate the anterior and middle
fossae.
Its lateral portions roof in the orbital cavities and support the frontal lobes of the cerebrum; they are convex and marked by depressions for the brain convolutions, and grooves for branches of the meningeal vessels.
The central portion corresponds with the roof of the nasal cavity
, and is markedly depressed on either side of the crista galli
.
It presents, in and near the median line, from before backward, the commencement of the frontal crest for the attachment of the falx cerebri
; the foramen cecum
, between the frontal bone
and the crista galli of the ethmoid, which usually transmits a small vein from the nasal cavity to the superior sagittal sinus
; behind the foramen cecum, the crista galli, the free margin of which affords attachment to the falx cerebri
; on either side of the crista galli, the olfactory groove formed by the cribriform plate
, which supports the olfactory bulb and presents foramina for the transmission of the olfactory nerves, and in front a slit-like opening for the nasociliary nerve
.
Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina
; the anterior, situated about the middle of the lateral margin of the olfactory groove, transmits the anterior ethmoidal vessels and the nasociliary nerve; the nerve runs in a groove along the lateral edge of the cribriform plate to the slit-like opening above mentioned; the posterior ethmoidal foramen
opens at the back part of this margin under cover of the projecting lamina of the sphenoid, and transmits the posterior ethmoidal vessels and nerve.
Farther back in the middle line is the ethmoidal spine
, bounded behind by a slight elevation separating two shallow longitudinal grooves which support the olfactory lobes.
Behind this is the anterior margin of the chiasmatic groove
, running laterally on either side to the upper margin of the optic foramen.
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....
, 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, and the small wings and front part of 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 limited behind by the posterior borders of the small wings of the sphenoid and by 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...
. The lesser wings of the sphenoid separate the anterior and middle
Middle cranial fossa
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....
fossae.
Overview
It is traversed by the frontoethmoidal, sphenoethmoidal, and sphenofrontal sutures.Its lateral portions roof in the orbital cavities and support the frontal lobes of the cerebrum; they are convex and marked by depressions for the brain convolutions, and grooves for branches of the meningeal vessels.
The central portion corresponds with the roof of the nasal cavity
Nasal cavity
The nasal cavity is a large air filled space above and behind the nose in the middle of the face.- Function :The nasal cavity conditions the air to be received by the other areas of the respiratory tract...
, and is markedly depressed on either side of the crista galli
Crista galli
The crista galli is a median ridge of bone that projects from the cribriform plate of the ethmoid bone.It is where the falx cerebri attaches anteriorly to the skull....
.
It presents, in and near the median line, from before backward, the commencement of the frontal crest for the attachment of the falx cerebri
Falx cerebri
The falx cerebri, also known as the cerebral falx, so named from its sickle-like form, is a strong, arched fold of dura mater which descends vertically in the longitudinal fissure between the cerebral hemispheres....
; the foramen cecum
Foramen cecum (frontal bone)
The frontal crest of the frontal bone ends below in a small notch which is converted into a foramen, the foramen cecum , by articulation with the ethmoid....
, between 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....
and the crista galli of the ethmoid, which usually transmits a small vein from the nasal cavity to the superior sagittal sinus
Superior sagittal sinus
The superior sagittal sinus , within the human head, is an unpaired area along the attached margin of falx cerebri. It allows blood to drain from the lateral aspects of anterior cerebral hemispheres to the confluence of sinuses...
; behind the foramen cecum, the crista galli, the free margin of which affords attachment to the falx cerebri
Falx cerebri
The falx cerebri, also known as the cerebral falx, so named from its sickle-like form, is a strong, arched fold of dura mater which descends vertically in the longitudinal fissure between the cerebral hemispheres....
; on either side of the crista galli, the olfactory groove formed by 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....
, which supports the olfactory bulb and presents foramina for the transmission of the olfactory nerves, and in front a slit-like opening for the nasociliary nerve
Nasociliary nerve
The nasociliary nerve is a branch of the ophthalmic nerve. It is intermediate in size between the two other main branches of the ophthalmic nerve, the frontal nerve and the lacrimal nerve, and is more deeply placed.-Path:...
.
Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina
Ethmoidal foramina
Ethmoidal foramina can refer to:* anterior ethmoidal foramen* posterior ethmoidal foramen...
; the anterior, situated about the middle of the lateral margin of the olfactory groove, transmits the anterior ethmoidal vessels and the nasociliary nerve; the nerve runs in a groove along the lateral edge of the cribriform plate to the slit-like opening above mentioned; the posterior ethmoidal foramen
Posterior ethmoidal foramen
Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina .The posterior ethmoidal foramen opens at the back part of this margin under cover of the projecting lamina of the sphenoid, and transmits the posterior ethmoidal vessels and nerve....
opens at the back part of this margin under cover of the projecting lamina of the sphenoid, and transmits the posterior ethmoidal vessels and nerve.
Farther back in the middle line is the ethmoidal spine
Ethmoidal 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...
, bounded behind by a slight elevation separating two shallow longitudinal grooves which support the olfactory lobes.
Behind this is 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...
, running laterally on either side to the upper margin of the optic foramen.