Transcript Slide 1

OSTEOLOGY
The Skull
The Skull
•
1.
2.
The skull is divided into two
parts:
Neurocranium- which forms a
protective case or “vault”
around the brain
Viscerocranium- which forms
the anterior part of the skull
including the orbits, nasal
cavities and upper/lower jaw
bones
Neurocranium
Viscerocranium
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2
The Skull
Frontal
coronal suture
Parietal
Occipital
Temporal
Sphenoid
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3
The Skull
Lacrimal
Nasal
Zygomatic
Nasal
Maxilla
Inferior Nasal
Conchae Inferior
maxilla
Nasal
conchae
Vomer
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Vomer
Mandible
Mandible
4
Frontal Bone
• Squamous (flat) portion
forms the skeleton of the
forehead
Frontal
Bone
Squamous
portion
• Fontal bone forms the roof
of the orbit
Nasion
Frontal
bone
Glabella
Glabella
Nasion
• Nasion is an area where
the frontal bone intersects
with the nasal bones
Orbital
portion
• Glabella- smooth, slightly
depressed area located
just superior to the nasion
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Frontal Bone
•
Supraorbital marginmarks the boundary
between the squamous
and orbital portions
•
Supraorbital notch or
foramen is for the passage
of the supraorbital nerve
and vessels
•
A prominent ridge just
superior to the supraorbital
margin is the superciliary
arch (more pronounced in
males)
•
Zygomatic process of the
frontal bone articulates
with the zygomatic bone
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Supraorbital
notch
Superciliary
arch
Zygomatic
process
Supraorbital
margin
6
Zygomatic Bones
• Cheek bones
• Forms a portion of the lateral
wall of the orbit
• Frontal Process of the
zygomatic bone articulates with
the frontal bone
Frontal
process
• Temporal process of the
zygomatic bone articulates with
the temporal bone
• Zygomaticofacial foramensmall foramen for passage of
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the zygomaticofacial nerve
Temporal
process
Zygomaticofacial
foramen
7
Maxillae
• Forms the upper jaw
• Alveolar processes of the
maxillae includes the
sockets and supporting
bone for the maxillary teeth
• Maxillae form the floor of
the orbit
• Large infraorbital
foramen for passage of the
infraorbital nerve & vessels
Infraorbital
foramen
Alveolar
process
Piriform
aperture
Maxilla
• Surrounds most of the
pear-shaped piriform
aperture
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Maxillae
• Frontal processes of the
maxillae articulates with
the frontal bone
• Zygomatic processes of
the maxillae articulates
with the zygomatic bones
• Anterior nasal spinesharp prominence at
inferior aspect of the
piriform aperture
frontal
process
• Intermaxillary suturesite where the two maxilla
are united in the median
plane
Zygomatic
process
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Anterior
nasal
spine
Intermaxillary
suture
9
• Seen within the piriform
aperture are the scrolled
middle nasal conchae
(part of the ethmoid bone)
& the inferior nasal
conchae
• Vomer bone along with
the perpendicular plate
of the ethmoid bone
which together form the
bony nasal septum can
also be identified with the
piriform aperture
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Perpendicular
plate
Middle &
Inferior
concha
Vomer
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Mandible
• U-shaped bone with alveolar
process that houses the
mandibular teeth
• Mental foramen- located
inferior to 2nd premolar for
passage of the mental nerve
and vessels
• Mental protuberance- a
triangular elevation of bone
that forms the prominence of
the chin
• Mental tubercle- located just
lateral to the protuberance
• Body is the horizontal
Alveolar
process
portion
• Ramus is the vertical portion
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Ramus
Body
Mental
foramen
Mental protuberance
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Osteology
Lateral Aspect of the Skull
Lateral Aspect of the Skull
1. Parietal bone
2. Frontal bone
3. Occipital bone
4. Temporal bone
5. Sphenoid bone
6. Mandible
7. Zygomatic bone
8. Maxillae
9. Lacrimal bone
10. Nasal bone
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1.
2.
9.
5.
4.
10.
3.
7.
8.
6.
13
Parietal Bones
• Paired bones that form the
lateral & superior cranium
• Temporal Lines- mark the
attachment site of the
temporalis muscle &
fascia
Coronal suture
Temporal
lines
Parietal
Lambdoid
suture
• Articulates with frontal
bone via coronal suture
• Articulates with occipital
bone via lambdoid suture
• Pterion-site where 4
cranial bones articulateimportant clinical
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implications
pterion
14
Temporal Bones
•
•
•
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Paired bones that form
the inferior lateral aspect
of skull
Squamous
Temporal bone is
described as having a flat
squamous portion and a
mastoid process (site of
attachment of several
muscles)
Mastoid
process
Zygomatic arch extends
anteriorly to articulate
with the zygomatic bone
Zygomatic arch
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Temporal Bones
•
External acoustic
meatus (ear canal) and
the pointed styloid
process are considered
to be located the
tympanic portion of the
temporal bone
•
Styloid process serves
as the attachment site for
several muscles and the
stylohyoid ligament
External
acoustic
meatus
Styloid process
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Temporal Bones
• Mandible and a portion of
the zygomatic arch
removed in this view
• Located on the inferior
aspect of the arch is a
small bony protrusionarticular tubercle that is
important in the
mechanics of the TMJ
• Mandibular fossa- deep
recess that accepts the
condyle of the mandiblealso important region of
the TMJ
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Articular
tubercle
Mandibular
fossa
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Zygomatic bone
• Forms major portion of the
cheek
• Temporal process that
articulates with the the
zygomatic arch
Zygomatic arch
Frontal process
• Frontal process that
articulates with the frontal
bone
• Zygomaticofacial
foramen – small foramen
generally visible
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Zygomaticofacial
foramen
Temporal process
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Occipital Bone
• Forms the posterior
aspect of the skull
• Articulates with the
parietal bone via the
lambdoid suture
• Prominent palpable
elevation located
posteriorly is the external
occipital protuberance
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Lambdoid
suture
External
Occipital
protuberance
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Sphenoid Bone
•
•
1.
2.
3.
4.
•
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Irregular shaped bone that
forms a portion of the
orbit, lateral aspect of skull
and a portion of the cranial
base
Sphenoid can be divided
into 4 parts:
Greater wing
Lesser wing
Pterygoid processes
Body
Some portions of the
sphenoid can only be
seen inside the cranial
cavity
Sphenoid Bone
20
4 portions of Sphenoid Bone
• Portion of zygomatic arch and
mandible removed in this view
• Greater wing articulates with
the temporal, parietal & frontal
bones at the pterion
Greater wing
• Pterygoid processes are two
thin plates of bone that serve
as attachment sites for muscles
• Pterygoid hamulus-small
hook of bone extending from
the medial pterygoid platetensor veli palatini tendon
courses around this
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Pterygoid
hamulus
Pterygoid
process
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Maxillae
• Portion of zygomatic arch and
mandible removed in this view
• Posterior aspect of the
maxillae is referred to as the
tuberosity of maxillae
• Small alveolar foramina for
the posterior superior alveolar
nerves & vessels
• Pterygomaxillary fissuretear-drop shaped fissure
between the sphenoid and
Alveolar
tuberosity of the maxillae
foramen
• Pterygopalatine fossa is a
small but important space
located medial to the fissure
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Pterygomaxillary
Fissure
Tuberosity of
maxilla
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Lateral Aspect of Skull
• Nasal bone can also
identified as it articulates
with the frontal bone and
the maxillae
• Lacrimal bone- which
houses the lacrimal sac
van be identified within the
orbit
• Prominent anterior nasal
spine at the inferior
aspect of the piriform
aperture
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Lacrimal bone
Nasal
bone
Nasal
spine
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Mandible
• Condylar process is
located at the superior
part of the ramus and
involved in the articulation
of the mandible with the
temporal bone (TMJ)
• Coronoid process is
located just anterior and
serves as the attachment
site for the temporalis
muscle
• Angle of mandible is
between the ramus and
body
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Condylar
process
Coronoid
process
Angle
24
Mandible
Condylar Process
Mandibular
foramen
Infant
Coronoid process
Mylohyoid line
Lingula
Ramus
Alveolar Part (crest)
Mental foramen
Body
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Mandible
Mandibular notch
Condylar process
Ramus
Body
Mental spines
Bone loss due to tooth loss
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Calvaria
• Emissary foramen- small,
inconsistent (not always
present) foramina for
passage of emissary veins
• Bregma- is the landmark
formed by the intersection of
the sagittal & coronal sutures
• Lambda-is the landmark
formed by the intersection of
the sagittal & lambdoid
sutures
Bregma
Coronal
suture
Sagittal
suture
Emissary
foramen
Lambda
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Lambdoid
suture
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Calvaria
• Inferior aspect of the skull
cap presents several
Diploe
features:
• Vascular grooves for
branches of the middle
meningeal artery
• Granular Foveolae- pits
formed by arachnoid
granulations (site of CSF
transfer)
• Groove for the superior
sagittal sinus-large
venous channel within the
dura mater
• Diploe- cancellous bone
containing red marrow
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Grooves for
middle
meningeal
artery
Granular
foveolae
Groove for superior
sagittal sinus
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Infant Skull
Superior & Lateral Aspects
Infant Skull
• Bones forming the calvaria &
some parts of the cranial
base develop by
Anterior
intramembranous
ossification
• Whereas-most parts of the
cranial base develop by
endochondral ossification
• Bones in the infant skull are
separated by areas of fibrous
tissue membranes- the
fontanelles:
• Anterior
Sphenoidal
• Posterior
• Mastoid
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sphenoidal
Posterior
Mastoid
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Infant Calvaria
• Anterior Fontanelle (soft
spot) is the future site of
the bregma
• By about 18-24 monthsthe surrounding bones
fuse together and is no
longer palpable
• Posterior Fontanelle is
triangular and marks the
future site of the lambda
• Fusion of surrounding
bones occurs by about 12
months
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Fontanelles-
Anterior
fontanelle
Posterior
fontanelle
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membranous gaps (soft spots) in skull that permit growth
Infant Skull
•
Mastoid & sphenoidal
fontanelles fuse early in
infancy
• Palpation of fontanelles
during infancy enables
physicals to determine:
1. Growth progress of the
frontal & parietal bones
2. Degree of hydration of the
infant (a depressed
fontanelle indicates
dehydration)
3. Level of intracranial
pressure-bulging fontanelle
indicates increased
pressure on the brain
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Anterior
Sphenoidal
Posterior
Mastoid
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Osteology
External Aspect of the Cranial
Base
Cranial Base
•
1.
2.
3.
4.
5.
6.
•
Inferior aspect of the skull
presents six different bones:
Palatine processes of the
maxillae
Palatine bone
Sphenoid bone
Vomer
Temporal
Occipital bone
Numerous foramina can also be
identified
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1
2
3
4
5
6
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Cranial Base- Palate
• Hard palate is formed by
the palatine processes
of the maxillae and the
horizontal plates of the
palatine bone
• Small prominence
projecting posteriorly form
the hard palate in the
median plane is the
posterior nasal spine
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Palatine
processes
Horizontal
plate of the
Palatine bone
Posterior
nasal
spine
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Cranial Base- Palate
• Posterior to the central
incisors is a small
depression-incisive fossa
with a pair of canalsincisive canals for the
passage of the
nasopalatine nerves
Incisive
canals
Greater and
Lesser
Palatine
foramina
• Posterolaterally are the
greater & lesser palatine
foramen for passage of
the nerves & vessels of
the same name
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Cranial Base-Vomer
• Vomer-thin, flat unpaired
bone in the midline that
forms a major portion of
the bony nasal septum
• On either side of the
vomer are two large
openings- choanae
(posterior nasal apertures)
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Vomer
Choanae
37
Cranial Base- Sphenoid
•
Three parts of the
sphenoid bone can be
appreciated on the
inferior aspect of skull:
1. Greater wing
2. Medial pterygoid plate
Greater
wing
Lateral
pterygoid
plate
Medial
pterygoid
plate
3. Lateral pterygoid plate
•
Pterygoid fossa is
between the two
pterygoid plates
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Cranial Base- Sphenoid
•
•
•
Foramen ovale for
passage of the
mandibular division (V3)
of the trigeminal nerve
Foramen
ovale
Auditory
Tube-groove
Foramen spinosum- for
passage of the middle
meningeal artery
Foramen
spinosum
Groove for the
pharyngotympanic
(auditory) tube lies
medial to spinosum
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Cranial Base- Temporal
• Mastoid processprominence located
posteriorly on the temporal
bone
• Mastoid serves as the
attachment site for the
SCM and posterior belly of
the digastric muscles
• External acoustic
meatus (EAM) is located
just anterior to the mastoid
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EAM
Mastoid
process
40
Cranial Base- Temporal
• Styloid process- thin
bony process extending
inferior & anteriorly
• Styloid serves as
attachment site for
numerous muscles &
ligaments
Mandibular
fossa
Styloid
process
• Mandibular fossaarticular surface that
accepts the condyle of the
mandible forming the TMJ
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Cranial Base- Temporal
• Two important foramen
can be identified on the
inferior aspect of the
temporal bone:
• Stylomastoid foramenlocated between the
mastoid & styloid
processes is a small
foramen for the passage
of the facial nerve (CN VII)
Carotid canal
Stylomastoid
foramen
• Carotid canal- passage for
the internal carotid artery
into the cranial cavity
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Cranial Base- Occipital
•
Occipital bone forms the
posterior and inferior
aspects of the skull
• Foramen Magnum- a
large foramen for
passage of the spinal
cord
• Foramen magnum
divides the occipital bone
into 3 parts:
1. Basilar Region
2. Condylar Region
3. Squamous Region
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1
2
Foramen
magnum
3
43
Cranial Base- Occipital
•
•
Basilar portion presents
a small tuberclepharyngeal tubercle for
attachment of the
pharyngeal constrictors
Foramen
lacerum
Pharyngeal
tubercle
Foramen lacerum
(jagged-shaped) is
located lust lateral to the
basilar portion
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Cranial Base- Occipital
•
•
•
Condylar portion presents
the occipital condyles that
articulate with the atlas
Jugular foramen- large
foramen between the
occipital & temporal bones
for passage of cranial
nerves: IX, X, XI and the
internal jugular vein
Jugular
foramen
Occipital
condyle
Hypoglossal
canal
Hypoglossal canal for
passage of the hypoglossal
nerve (CN XII)
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Cranial Base- Occipital
•
Squamous portion
presents the palpable
external occipital
protuberance
•
Superior & inferior
nuchal lines project
laterally and are sites
for muscular
attachments
Superior &
inferior
nuchal lines
External
occipital
protuberance
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Osteology
Internal Aspect of the Cranial
Base
Cranial Base
•
Internal aspect of the
cranial base is divided
into three major regions
or fossae:
1. Anterior cranial fossa
2. Middle cranial fossa
3. Posterior cranial fossa
Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
•
These three fossae lie at
different levels and form
the bowl-shaped floor of
the cranial cavity
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Anterior Cranial Fossa
Ethmoid
•
Frontal lobes of the
brain occupies the
anterior cranial fossa
• Fossa is formed by the:
1. Orbital portion of the
frontal bone
2. Ethmoid bone in the
middle
3. Lesser wing of the
sphenoid
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Orbital portion of
the frontal bone
Lesser wing of
the sphenoid
49
Anterior Cranial Fossa
•
Frontal crest- a median
bony extension from the
frontal bone
Crista
galli
•
Foramen cecum is located
at the base of the crest and
is a small foramen for
passage a vessels during
development
•
Crista galli- ridge of bone
projecting superiorly from
the ethmoid bone and
serves as the attachment
for the cerebral falx
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Frontal crest
Foramen cecum
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Anterior Cranial Fossa
•
•
On either side of the
crista galli is a “sievelike”
Cribriform plate for
passage of the olfactory
axons into the cranial
cavity
Cribriform plate
Optic canal for passage
of the optic nerve (CN II)
and the ophthalmic
Optic canal
artery can be
appreciated within the
lesser wing of the
sphenoid
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Middle Cranial Fossa
•
Temporal lobes of the
brain occupy the middle
cranial fossa
• Fossa is formed by the:
1. Greater wing of the
sphenoid
2. Squamous portion of the
temporal bone
3. Petrous portion of the
temporal bone
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Greater wing
of sphenoid
Squamous
portion temporal
bone
Petrous portion
temporal bone
52
Middle Cranial Fossa
• Sella turcica- the saddlelike bony formation
located on the superior
aspect of the body of the
sphenoid
Sella
turcica
Anterior and
Posterior clinoids
• Sella turcica is surrounded
by anterior & posterior
clinoid processes
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Middle Cranial Fossa
•
Sella turcica is
composed of three parts:
1. Hypophyseal fossa
(pituitary fossa)
2. Tuberculum sellae
(saddle horn)
3. Dorsum Sellae (back of
the saddle)
•
Tuberculum sellae
Hypophyseal fossa
Dorsum sellae
Sella turcica- essentially
houses and guards the
pituitary gland
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Middle Cranial Fossa
•
Middle cranial fossa
presents five important
foramina:
1. Superior orbital
fissure for passage of
CN’s III, IV, V1 & VI &
ophthalmic veins
2. Foramen rotundum
which transmits the
maxillary nerve (V2)
Superior orbital fissure
Foramen rotundum
Foramen ovale
3. Foramen ovalewhich transmits the
mandibular nerve (V3)
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Middle Cranial Fossa
4. Foramen spinosum
which transmits the middle
meningeal artery
5. Foramen lacerumnothing is transmitted
vertically thru this foramen
although the internal
carotid artery and some
nerves pass across the Foramen
lacerum
foramen horizontally
•
Foramen spinosum
Petrosal grooves
Grooves for the greater &
lesser petrosal nerves
are located along the
anterior slope of the
petrous portion of the
temporal bone
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Middle Cranial Fossa
•
Petrous portion of the
temporal bone houses
the middle and inner ear
cavities
•
Arcuate eminencemarks the roof of the
anterior semicircular
canal of the inner ear
cavity
•
Trigeminal impression
Arcuate eminence
Trigeminal impression is
located just anteromedial
the eminence-which
marks the location of the
sensory ganglion of the
trigeminal nerve
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Posterior Cranial Fossa
• The largest & deepest of
the three fossae
• Cerebellum, pons and
medulla occupy the
posterior fossa
• Formed mainly by the
occipital bone and the
petrous & mastoid
portions of the temporal
bone
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Occipital
bone
Temporal bone
Petrous portion
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Posterior Cranial Fossa
• Clivus marks the
anterior portion of the
occipital bone
• Foramen magnumlarge foramen that marks
the transition from the
medulla to the spinal
clivus
cord
• Posterior to the foramen
magnum is the internal
occipital crest and
internal occipital
protuberance
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Occipital crest
Internal occipital
protuberance
59
Posterior Cranial Fossa
•
Broad grooves show the
horizontal course of the
transverse and S-shaped
sigmoid sinuses (both dural
venous sinuses)
•
Sigmoid sinus empties into
the large jugular foramen
which also transmits several
Jugular
cranial nerves:
foramen
1. Glossopharyngeal (CN IX)
2. Vagus (CN X)
3. Accessory (CN XI)
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Groove for the
Sigmoid sinus
Transverse
Sinus groove
60
Posterior Cranial Fossa
• Internal acoustic meatus is
located just anterosuperior to
the jugular foramen
• Internal acoustic meatus
transmits the facial nerve
(CN VII) and
vestibulochochlear nerve
(CN VIII) along with the
labyrinthine artery
Hypoglossal
Internal
acoustic
meatus
canal
• Hypoglossal canal for the
hypoglossal nerve (CN XII)
lies superior to the margin of
the foramen magnum
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Cribrifrom plate-CN I
Superior Orbital Fissure
CN III, IV, V1 & VI
Optic Canal CN II
Foramen Rotundum- CN V2
Foramen Ovale-CN V3
Hypoglossal Canal
CN XII
Internal Acoustic MeatusCN VII & VIII
Jugular Foramen- CN IX, X and XI
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Osteology of the Orbit
• Seven bones articulate to
make each orbit:
superior
1. Frontal
2. Zygomatic
3. Maxillary
4. Lacrimal
5. Ethmoid
6. Palatine
7. Sphenoid
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1
lateral
7
2
5
6
4
medial
3
inferior
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Osteology of the Orbit
• Optic canal- transmits the
optic nerve and
ophthalmic artery
• Superior orbital fissuretransmits CN III, IV, V1 &
VI
Ethmoidal
foramina
Optic canal
• Inferior orbital fissure &
groove- transmits the
infraorbital vessels &
nerve
• Anterior & posterior
ethmoidal foraminatransmits vessels & nerves
with same name
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Superior
orbital
fissure
Inferior
orbital
fissure &
groove
64