Download Interior of skull

Interior of skull
The Cranial Fossae
Cranial fossa – curving depression of
the cranial floor
Anterior cranial fossa formed by:
frontal bone, ethmoid, lesser wing
of the sphenoid;
cradles the frontal lobes of the
cerebral hemispheres
 Middle cranial fossa is formed by:
sphenoid, temporal, parietal bones;
cradles the temporal lobes of the
cerebral hemispheres, the
diencephalon, and mesencephalon
 Posterior cranial fossa is formed primarily by:
occipital bone, with contributions from the temporal and parietal bones
- suports the occipital lobes of the crebral hemispheres, the crebellum,
and the pons and medulla oblongata (brain stem)
The Cranial Fossae
Interior of the Cranial Cavity
Cranial cavity: occupied by the brain
 Calvaria (skull cap): upper
dome-like portion of skull
 Floor divided into anterior,
middle, and posterior fossae
 Crista galli: prominent ridge
in center of anterior fossa.
Point of attachment for the
dura mater (one of the
meninges)
 Olfactory fossae lateral to
crista galli. Olfactory bulb
within
 Cribriform plate of the
ethmoid forms floor of
olfactory fossae
 Olfactory nerves pass through the foramina of the cribriform plate
 Sella turcica: part of sphenoid bone that houses the pituitary gland
 Foramen magnum: opening where brain attaches to spinal cord
Middle cranial Fossa
 Deeper than the preceding, is narrow in the middle, and wide at the sides
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of the skull.
It is bounded
in front by the posterior margins of the small wings of the sphenoid, the
anterior clinoid processes, ridge forming the anterior margin of the
chiasmatic groove;
behind, by the superior angles of the petrous portions of the temporals
and the dorsum sella
laterally by the temporal squama, sphenoidal angles of the parietals, and
great wings of the sphenoid.
 It is traversed by the
 squamosal,
 sphenoparietal,
 sphenosquamosal,
 sphenopetrosal sutures.
 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 (optic groove)
 Tuberculum sella
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In the sphenoid bone, behind the chiasmatic groove is an elevation,
the tuberculum sellae.
 sella turcica
 Deep depression Behind the tuberculum sella
 Contains the fossa hypophyseos, which
lodges the hypophysis, and presents on its
anterior wall the middle clinoid processes
 Bounded posteriorly by a quadrilateral plate
of bone, the dorsum sella, upper angles are
surmounted by the posterior clinoid
processes
 Gives 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
 Optic foramen
The optic foramen is the opening to the optic canal.
 Transmits the optic nerve and ophthalmic artery (with accompanying
sympathetic nerve fibres) into the orbital cavity.
Behind the optic foramen the anterior clinoid process is directed
backward and medialward and gives attachment to the tentorium
cerebelli
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 Superior orbital fissure
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Bounded
 Above by the small wing
 Below, by the great wing,
 Medially, by the body of the sphenoid
 Laterally by the orbital plate of the frontal bone.
Transmits to the orbital cavity
oculomotor, trochlear, ophthalmic division of the trigeminal, abducent
nerves, some filaments from the cavernous plexus of the sympathetic,
the orbital branch of the middle meningeal artery;
From the orbital cavity
Recurrent branch from the lacrimal artery to the dura mater, and the
ophthalmic veins
 Foramen rotundum
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Behind the medial end of the
superior orbital fissure
Provides passage for the maxillary
nerve.
 Foramen ovale
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At base of lateral pterygoid plate
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Through which passes mandibular
nerve, accessory meningeal
artery, & lesser petrosal nerve
 Foramen spinosum
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Posterior & somewhat lateral
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to foramen ovale
Transmits middle meningeal
vessels & small meningeal
branch of mandibular
Foramen lacerum
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At base of medial pterygoid
plate in dried skull
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Not complete foramen in intact body, because its inferior part is
covered over by fibrocartilaginous plate, across superior (inner
or cerebral) surface of which passes internal carotid artery.
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Carotid canal
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Inferior surface of petrous temporal bone is pierced by round
opening.
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Internal carotid artery, coursing within canal, immediately takes
right angle turn to reach side of foramen lacerum.
Hiatus for greater petrosal nerve (or hiatus of the facial canal)
 A shallow groove, sometimes double, leading lateralward and backward
to an oblique opening for the passage of the
 greater superficial petrosal nerve
 petrosal branch of the middle meningeal artery.
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Facial canal (also known as Fallopian Canal) is a
Z-shaped canal running through the temporal
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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
It is located within the middle ear region, according to its shape it is
divided into three main segments: the labyrinthine, the tympanic, and
the mastoidal segment.
Posterior cranial Fossa
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The posterior fossa is the largest and deepest of the three.
It is formed by
 Dorsum sella and clivus of the sphenoid
 Occipital
 Petrous and mastoid portions of the temporals
 Mastoid angles of the parietal bones
Crossed by the
 occipitomastoid suture
 parietomastoid sutures
lodges the cerebellum, pons, and medulla
oblongata.
 Foramen magnum
 Posterior to basilar portion of occipital
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bone
Transmits
Medulla oblongata & its membranes
Accessory nerves
Vertebral arteries
Anterior & posterior spinal arteries
Ligaments connecting occipital bone with
axis
Hypoglossal canal
 Courses forward & laterally from inner
aspect of occipital bone within cranium just above foramen
magnum to opening that perforates occipital bone externally at
lateral part of base of occipital condyle
 Transmits hypoglossal nerve & a branch of posterior meningeal
artery
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Jugular foramen is situated between the lateral part of the occipital and
the petrous part of the temporal
 Anterior compartment – inferior petrosal sinus
 Intermediate – glossopharyngeal, vagus, &
accessory nerves
 Posterior – sigmoid sinus which leads to internal
jugular vein, & some meningeal branches from
occipital & ascending pharyngeal arteries
 Internal auditory meatus (also internal acoustic
meatus,) is a canal in the petrous part of the
temporal bone of the skull that carries nerves from
inside the cranium towards the middle and inner
ear compartments
 Namely cranial nerve VII and cranial nerve VIII.
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