Anatomy of the skull
Dr Rania Gabr
Objectives
1.List the bones of the skull
2.Identify the major sutures of the skull
3.Identify the major surface markings of the skull
4.Identify the major foramina in the skull
5.List the major structures which pass through the
foramina
6.Describe the cranial fossa and its part
7.Understand the base of the skull and its fracture
8.Describe the structure of the mandible
The Skull
• It consists of flat and
irregular bones
• It is divided into:
Cranial bones which encase
the brain (Neurocranium)
Facial bones which form
the bones of the face
(Viscerocranium)
The Skull
• Cranial bones include:
(Neurocranium)
Frontal 1
Ethmoid 1
Sphenoidal 1
Occipital 1
Parietal 2
Temporal 2
• Facial bones include:
(Viscerocranium)
Maxilla 2
Zygomatic 2
Nasal 2
Palatine 2
Lacrimal 2
Inferior conchae 2
Vomer 1
Mandible 1
The Skull
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Frontal
Maxilla
Zygomatic
Nasal
Mandible
Lacrimal
• z
The Skull
• Parietal
• Temporal
Squamous
Mastoid
Styloid
Tympanic
Petrous
• Sphenoid
Greater wing
Lesser wing
Pterygoid process
Body
• Occipital
The Skull
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Petrous part of temporal
Lesser wing of sphenoid
Body of sphenoid
Pterygoid process
Ethmoid bone
Crista galli
Cribriform plate
Perpendicular plate
• Vomer
• Palatine bone
Frontal Bone
• Landmarks:
– Squama: flat portion that
forms the forehead
– Supraorbital margin: ridge
under the eyebrow, forming
the upper part of the orbit
(eye socket)
– Supraorbital foramen:
small hole within supraorbital
margin for blood vessels and
nerves
– Frontal sinuses: hollow
spaces behind the squama,
act as sound chambers to give
the voice resonance.
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Frontal Bone (Anterior View) (Blue Colored Bone)
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Frontal Bone (Lateral View) (Blue Colored Bone)
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Temporal bone
• Landmarks:
Temporal bone
– Squama: flat portion of the temporal bone forming the anterior
and superior part of the temple
– Zygomatic process: process forming part of the cheek
– Petrous portion: internal, forming part of the floor of the cranium.
Contains the ear canal and internal ear structures.
– Mandibular fossa: socket between squama and petrous portion,
articulates with the condyle of the mandible (TMJ)
– External auditory meatus: opening to the ear canal
– Mastoid process: bony prominence behind the external auditory
meatus
– Styloid process: looks like an elephant’s tusk located between the
mastoid process and the jaw. Acts as a point of attachment for
muscles and ligaments.
Temporal Bone (Lateral View) (Purple Colored Bone)
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Occiput
• Landmarks:
– Foramen magnum: large
hole, allowing passage of the
spinal cord
– External occipital
protuberance (EOP):
prominent projection on back
of occiput
– Nuchal lines: a superior and
inferior line running laterally
from the midline, serve as a
point of muscle attachment
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Occipital Bone (Lateral View) (Orange Bone)
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Occipital Bone (Posterior View) (Orange Colored Bone)
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Sphenoid Bone
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Sphenoid bone
• A prominent, irregular, wedge-shaped bone at the base of the
skull. The sphenoid bone has been called the "keystone" of the
cranial floor since it is in contact with all of the other cranial
bones.
• Landmarks
– Greater wings: large lateral projections of bone that help to
form the lateral border of the skull
– Lesser wings: smaller lateral projections of bone above the
greater wings
– Pterygoid processes: two long downward projections from
the greater wings that act as a point of muscle attachment.
– Sella turcica: known as the Turkish Saddle which cradles the
pituitary gland.
Sphenoid Bone (Lateral View) (Green Colored Bone)
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Sphenoid Bone (Floor of Cranium) (Green Colored Bone)
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Ethmoid Bone
• An irregularly shaped, spongy bone that
provides the floor of the front part of the
skull and the roof of the nasal cavity.
• The ethmoid consists of two masses of thin
plates enclosing air cells and looks like a
sieve.
• Landmarks:
– Lateral masses: form most of the wall
between the nasal cavity and the orbits
– Perpendicular plate: forms the superior
portion of the nasal septum
– Cribriform plate: forms the roof of the
nasal cavity
– Olfactory foramina: small holes within
the cribriform plate for passage of the
first cranial nerve (for smell)
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– Crista galli: upward
extension of bone above the
cribriform plate, acts as an
anchoring point for one of
the coverings of the brain. (
Falx cerebi)
– Nasal conchae (turbinates):
two scroll-shaped
projections (superior and
middle) with a mucus
membrane on either side of
the nasal septum. Function
to cause air turbulence and
trap inhaled particles.
Bones of the face
Maxilla
• The second largest bones of the face, after the
mandible and form, by their union, the whole
of the upper jaw.
• They hold the upper teeth, and connect on the
left and right to the zygomatic bones (cheek
bones).
• Each assists in forming the boundaries of three
cavities, namely, the 1-roof of the mouth, 2-the
floor and lateral wall of the nose, and 3- the
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floor of the orbit.
Maxilla
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Landmarks:
Infra Orbital foramen:
hole below the orbit,
for blood vessels and
nerves
Alveolar process:
arch of the maxilla
containing the upper
teeth
Palatine process:
horizontal projection of
the maxilla forming the
anterior ¾ of the hard
palate.
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Zygomatic Bones
Commonly referred to as
the cheekbone.
It is situated at the upper
and lateral part of the
face: it forms the
prominence of the cheek
and part of the lateral wall
and floor of the orbit.
It articulates with the
zygomatic arch of the
temporal bone.
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Vomer
One of the unpaired
facial bones of the
skull.
Located in
the midsagittal line,
and attaches to the
sphenoid, the
ethmoid, the left and
right palatine bones,
and the left and right
maxillary bones.
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Inferior Nasal Conchae
Extends horizontally
along the lateral wall
of the nasal cavity
and consists of a
lamina of spongy
bone, curled upon
itself like a scroll.
Inferior Nasal Conchae
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Lacrimal Bones
Smallest and most
fragile bone of the
face, is situated at
the front part of the
Medial of the
orbit.
Lacrimal bone
Contains the lacrimal
sac and the nasolacrimal duct.
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Nasal Bones
Varying in size and
form in different
individuals
They are placed side by
side at the middle and
upper part of the face
and form, by their
junction, "the bridge" of
the nose
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Cranial Fossa
• It is the cavity of the
skull
• Divides into:
Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
Anterior Cranial Fossa
• Formed of:
Orbital plate of frontal bone
Cribriform plate of ethmoid
Crista galli
Lesser wing of sphenoid
• Occupied by:
Frontal lobe of the cerebrum
Optic nerves
Olfactory bulb and tract
Middle Cranial Fossa
• Formed of:
Greater wing of sphenoid
Body of sphenoid
Squamous part of temporal bone
Anterior part of petrous bone
• It occupied by:
Temporal lobe of the cerebrum
Posterior Cranial Fossa
• Formed of:
Sphenoid part of clivus
Posterior part of petrous bone
Occipital bone
• It shows the following land marks:
Groove for transverse sinus
Groove for sigmoid sinus
Internal occipital protuberance
• It is occupied by:
Cerebellum
Brain stem
Base of The Skull
• Most of the bones
are seen in other
views
Foramina of the Skull
• Foramina are found within the skull bones
• They vary in size and shape
• They transmit nerves, blood vessels and dura matter
Foramina of the Skull
• a
Foramina of the Skull
• Supraorbital
• Infraorbital
• Mental
• The following must be identified:
Nasion
Inion
Bregma
Lambda
External occipital protuberance
Parietal eminence
Zygomatic arch
Sutures of the Skull
• Sutures are fibrous
joints articulating the
skull bones
• They include:
Coronal
Sagittal
Lambdoid
Pterion
Skull Fontanelles
• Fontanelles are spaces between some of
the skull bones of infants.
• They permit easy growth of the brain.
• They permit overlapping of skull bones
during labor.
• They include:
1. Anterior Fontanelle

Lies between Frontal and Parietal
Bones

Closed by 18 months of age
2. Posterior Fontanelle

Lies between Parietal and Occipital
Bones

Closed by end of 1st year
3. Anterolateral Fontanelle
4. Posterolateral Fontanelle
The Mandible
• It is a flat bone
• Identify the following:
Head(condylar process)
Mandibular notch
Coronoid process
Ramus
Angle
Body
Mylohyoid line
Submandibular fossa
Digastric fossa
Mandibular foramen
Mental foramen
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