Download Skull

SKULL AS A WHOLE
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CRANIAL FOSSAE
LEARNING OBJECTIVES
At the end of this lecture , the
student should be able to know:
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Parts of skeleton (axial and appendicular)
Parts of skull
Sutures of skull
Different bones of skull
Different views (Norma) of skull
Interior of the skull
Divisions of the cranial fossa
Anterior cranial fossa
Foramens and strucutures passing through them
Middle, and posterior cranial fossa
Foramens and structures passing through them
The Axial Skeleton
• Eighty (80) bones
• It is composed of five parts;
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Skull
Ossicles of the middle ear
Hyoid bone of the throat
Vertebral column
Bony thorax
The Axial Skeleton
The skull
• The skull, body’s most complex bony
structure, is formed by the cranium and
facial bones (bones of face)
• Cranium –
– cranium encloses cranial cavity
– protects the brain and is the site of
attachment for head and neck
muscles
• Facial bones –
– Supply the framework of the face, the
sense organs, and the teeth
– Provide ,surround and protect the
entrances to the respiratory and
digestive tracts
– Anchor the facial muscles of
expression
Bones of skull
• Formed from eight large bones
– Paired bones include
• Temporal bones
• Parietal bones
– Unpaired bones include
• Frontal bone
• Occipital bone
• Sphenoid bone
• Ethmoid bone
Overview of Skull
Geography
• The skull contains approximately 85
named openings
– Foramina, canals, and fissures
– Provide openings for important
structures
• Spinal cord
• Blood vessels serving the brain
• 12 pairs of cranial nerves
SUTURES
• A suture is a type of fibrous joint which
only occurs in the skull (or "cranium").
• A tiny amount of movement is permitted at
sutures, which contributes to the
compliance and elasticity of the skull.
• Main sutures are:
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Sagittal
Coronal or Frontal
Squamosal
Lambdoidal
Sutural (Wormian) Bones
• Usually found in Lambdoidal suture
SUTURES OF LATERAL
SIDE
SUTURES OF OCCIPITAL
REGION
FONTANELLES IN
NEWBORN
• Fontanelles are soft spots on a baby's
head which, during birth, enable the bony
plates of the skull to flex, allowing the
child's head to pass through the birth
canal.
• The ossification of the bones of the skull
cause the fontanelles to close over by a
child's second birthday.
• The closures form the sutures of the
neurocranium.
FONTANELLES
FONTANELLES
STUDY OF SKULL
Skull can be studied from
different views.The views so
obtained are termed the
normae of the skull
– From Above- Norma Verticalis
– From Below- Norma Basalis
– From Front- Norma Frontalis
– From Back- Norma Occipitalis
– From Side- Norma Lateralis
– From Inside – Interior of skull
SKULL SUPERIOR VIEW (NORMA
VERTICALIS)
• Four sutures mark the articulations of the
parietal bones
– Coronal suture – articulation between parietal
bones and frontal bone anteriorly
– Sagittal suture – where right and left parietal
bones meet superiorly
– Lambdoid suture – where parietal bones meet
the occipital bone posteriorly
– Squamosal or squamous suture – where
parietal and temporal bones meet
INFERIOR VIEW OF THE SKULL
(NORMA BASALIS)
THE SKULL
ANTERIOR VIEW (NORMA
FRONTALIS)
• oval outline
• Limited
– above by the frontal bone
– below by the body of the mandible
– laterally by the zygomatic bones and the
mandibular rami.
SKULL POSTERIOR VIEW (NORMA
OCCIPITALIS)
• Circular outline.
• Forms most of skull’s posterior and base
• Major markings include
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Sagittal suture
Lamboidal suture
external occipital protuberance
mastoid foramen
foramen magnum,
occipital condyles
hypoglossal canal
Skull: Lateral View (Norma
Lateralis)
• Form most of the superior and
lateral aspects of the skull
MIDSAGITTAL LATERAL ASPECTS
OF THE SKULL
INTERIOR OF THE SKULL
(CRANIAL FOSSA)
THE CRANIAL FOSSAE
Cranial fossa – curving depression of the cranial floor
• Anterior cranial fossa formed by:
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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 SECTIONAL ANATOMY OF
THE SKULL
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)
INTERIOR OF THE
CRANIAL CAVITY
• 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
ANTERIOR CRANIAL
FOSSA
• The floor of the anterior fossa is formed by:
– Orbital plates of the frontal,
– Cribriform plate of the ethmoid
– 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.
• It is traversed by the
frontoethmoidal suture
sphenoethmoidal suture
sphenofrontal sutures.
ANTERIOR CRANIAL
FOSSA
• 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
• Foramen cecum,
– The frontal crest of the frontal bone ends
below in a small notch which is converted into
a foramen, by articulation with the ethmoid
– It transmits a vein from the nose to the superior
sagittal sinus
ANTERIOR CRANIAL
FOSSA
• Crista galli, ridge behind the foramen
cecum, the free margin of which affords
attachment to the falx cerebri
• Olfactory groove on either side of the
crista galli, formed by the cribriform plate,
• Supports the olfactory bulb and presents
foramina for the transmission of the
olfactory nerves,
• In front a slit-like opening for the
nasociliary nerve.
ANTERIOR CRANIAL
FOSSA
• Anterior ethmoidal foramen
– situated about the middle of the lateral
margin of the olfactory groove,
– Transmits the anterior ethmoidal vessels
and the anterior ethmoidal nerve
• Posterior ethmoidal foramen
– Opens at the back part of this margin under
cover of the projecting lamina of the sphenoid
– transmits the posterior ethmoidal vessels and
nerve
Identify??
Middle cranial Fossa
• Deeper than the preceding, is narrow in
the middle, and wide at the sides 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.
Middle cranial Fossa
• It is traversed by the
– squamosal,
– sphenoparietal,
– sphenosquamosal,
– sphenopetrosal sutures.
Middle cranial Fossa
• 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
– In the sphenoid bone, behind the
chiasmatic groove is an elevation, the
tuberculum sellæ
Middle cranial Fossa
• 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
Middle cranial Fossa
• 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.
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Behind the optic foramen the anterior clinoid process
is directed backward and medialward and gives
attachment to the tentorium cerebelli
Middle cranial Fossa
• Superior orbital fissure
• Bounded
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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
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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
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Recurrent branch from the lacrimal artery to the dura
mater, and the ophthalmic veins
Middle cranial Fossa
• Foramen rotundum
– Behind the medial end of the superior
orbital fissure
– Provides passage of the maxillary nerve.
• Foramen ovale
– At base of lateral pterygoid plate
– Through which passes mandibular nerve,
accessory meningeal artery, & lesser petrosal
nerve
• Foramen spinosum
– Posterior & somewhat lateral to foramen ovale
– Transmits middle meningeal vessels & small
meningeal branch of mandibular nerve
Middle cranial Fossa
• Foramen lacerum
– At base of medial pterygoid plate in dried skull
– 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.
• Carotid canal
– Inferior surface of petrous temporal bone is
pierced by round opening.
– Internal carotid artery, coursing within canal,
immediately takes right angle turn to reach
side of foramen lacerum.
Middle cranial Fossa
Hiatus for greater petrosal nerve (or
hiatus of the facial canal)
• A shallow groove, sometimes double,
leading lateral and backward to an
oblique opening for the passage of the
• greater superficial petrosal nerve
• petrosal branch of the middle meningeal
artery.
Middle cranial Fossa
• 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
• 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
• The posterior fossa is the largest and deepest of
the three.
• It is formed by
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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.
Posterior cranial Fossa
• Foramen magnum
– Posterior to basilar portion of
occipital bone
– Transmit
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Medulla oblongata & its membranes
Accessory nerves
Vertebral arteries
Anterior & posterior spinal arteries
Ligaments connecting occipital bone with
axis
Posterior cranial Fossa
• 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
Posterior cranial Fossa
• The 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
Posterior cranial Fossa
• The 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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