Cranial fossae - internal surface of skull is divided
into three cranial fossa
1. Anterior
Boundaries -
In front & sides - by frontal bone
Behind - free border of lesser wing of sphenoid
Anterior clinoid process
Anterior margin of sulcus chiamatis
They separate anterior from middle
Floor - cribriform plate of ethamoid
Anterior part of body of sphenoid
Orbital part of frontal bone
Lesser wing of sphenoid
Features -
1. in cribriform plate of ethamoid –it
separate the fossa from nasal cavity ie it
forms the roof
a) Crista galli - crest like elevation gives
attachment to falx cerebri
b) Foramina caecum - in front of Crista galli
for transmitting veins from nose to superior
saggital sinus
c) Anterior ethmoidal canal - behind & on
each side of Crista galli for anterior
ethmoidal vessels & nerves it is continuation
of nasocillary nerve
d) Posterior ethmoidal canal - at
posterolateral part of cribriform plate - for
posterior ethmoidal vessels & nerves it
branch of nasocillary nerve
e) Numerous foramina in cribriform plate
– for olfactory nerve 15 to 20 in no.
2. Anterior part of body of sphenoid
a) Jugum sphenidale - it separates the fossa
from sphenoidal air sinus it lodges gyrus
rectus & olfactory tract
b) Sulcus chiamatis - lodges the optic tract
3. Orbital part of frontal – it shows
impressions of cerebral gyri & support the
inferior surface of frontal lobe
It separates the anterior fossa from orbit &
anterior ethmoidal sinus
In front of cribriform plate there is frontal
crest
4. Lesser wing of sphenoid
a) Posterior free border - related to stem of
lateral sulcus of brain
b) Anterior clinoid process - prominent
projection posteromedially for attachment to
tentorium cerebelli
Middle cranial fossa --
Boundaries -
In front - posterior border of lesser wing
Anterior clinic process
Anterior margin of sulcus chimaticus
Behind - superior border of petrous temporal
Dorsum sellae of sphenoid
On each side - greater wing sphenoid
Squmous temporal
Bones taking part -
1. Central part - body of sphenoid
2. Lateral part on each side – by greater wing
sphenoid & temporal
Central part -
Features -
1. Optic grove - optic chiasma lies behind
2. Optic canal - for optic nerve & ophthalmic
artery
3. Sellae turcica - saddle like upper surface of
body of sphenoid
a) Hypophyseal fossa - in central part for
pituitary gland
b) Tuberculum sellae -in front a ridge which
represent junctional region between pre &
post sphenoidal part & diaphragma sellae is
attached
c) Dorsum sellae –a square plate of bone
forming back rest of upper end attachment
of diaphragma sellae
d) Posterior clinoid process – projection from
upper & lateral part of dorsum sellae
tentorium cerebella
e) Middle clinoid process - lateral end of
Tuberculum sellae
f) Carotid sulcus - shallow grove on each
side of body of sphenoid contains ICA &
cavernous sinus
3. Lateral part of middle cranial fossa
This fossa is related in front with orbit & laterally to
temporal fossa & below to infra temporal fossa
a) It lodges temporal lobe of brain
b) Superior orbital fissure – it is communication
between anterior part middle cranial fossa
with orbit
Boundary -
Above - lesser wing
Below – greater wing
Medially – body of sphenoid
Structure passing
a) Middle part - occulomotor nerve &
abducent nerve
b) Lateral part - trochlear nerve frontal nerve
lacrimal nerve middle meningeal artery
superior ophthalmic vein
c) Foramina rotundum – maxillary nerve
d) Foramina ovale - mandibular nerve
,ascending pharyngeal artery ,lesser petrosal
nerve ,emissary vein
e) Foramina spinosum –posterolateral to
ovale middle meningeal artery & emissary
vein
f) Foramina lacerum - posteromedial to
ovale meningeal branch of ascending
pharyngeal artery
g) Tegmen tympani – thin plate of bone
Posterior cranial fossa - deepest of three fossae
Boundaries -
In front - superior border of petrous part of
temporal
Posterior clinic process & dorsum sellae
Behind- Squmous part of occipital
On each side – mastoid part of temporal
Features central part
1. Clivus – a sloping area formed by fuse part
of posterior part of body of sphenoid &
basilar part of occipital
It is related with basilar artery it also support Pons
& medulla
2. Foramina magnum
Anterior structure –
Apical ligament
Cruciate ligament
Membrana tectoria
Posterior structure
a) Medulla oblongata with its meanings
b) Vertebral artery
c) Spinal accessory nerve
d) Anterior & posterior spinal arteries
3. Internal occipital crest - extends from
internal occipital protuberance to foramen
magnum for the attachment of falx cerebelli
4. Internal occipital protuberance –a projection
5. Transverse sulcus - sulcus running laterally
from Internal occipital protuberance which
lodges transverse sinus
Lateral area - on each side of fossa
1. Hypoglossal canal - ie anterior ethmoidal
canal transmits hypoglossal nerve &
meningeal branch of ascending pharyngeal
artery
2. Condylar canal - ie posterior ethmoidal canal
transmits emissary vein from sigmoid sinus
3. Jugular foramen-
Anterior part -
1. Inferior petrosal sinus
2. meningeal branch of ascending pharyngeal
artery
Middle part -
a) 9,10,11 cranial nerves
Posterior part -
1. Sigmoid sinus continued as internal jugular
vein
4. Internal acoustic meatus
a) Motor & sensory root of facial nerve
b) Vectibulo-cochlear nerve
c) Internal acoustic branch of basilar artery
5. Sigmoid sulcus - it is downwards continuation
of transverse sulcus contains sigmoid sinus
Applied anatomy
1. # to anterior cranial fossa results in
a) Black eye
b) Bleeding through nose
c) Discharge of CSF through nose
2. # to middle cranial fossa results in
a) Bleeding through ear
b) Discharge of CSF through ear
c) When it envolves sphenoid bone there may
be bleeding from mouth or nose
d) Vertigo may appear due to damage of
semicircular canal
3. # to posterior cranial fossa - it is very rare
