ﷲّ ورﺣﻤﺔ اﻟﺮﺣﯿﻢ
اﻟّﮫ
اﻟﺮﺧ َ ﺮ
ﺑِﺜْﻢ
وﺑﺮﻛﺎﺗﮫ
H u m a n Anatomy
L e c t u r e 1
Bones o f skull &Cranial f o r a m i n a
B y
Assistant professor
Dr. Hatem A Hatem
Collage of Medicine-In sina university
Department of Anatomy
2 0 2 3 - 2 0 2 4
Objectives of this lecture to know
about the bones of the skull:
• Cranium
• Face
• Sutures of the Skull
• Clinical Relevance.
Skull :
• Bony structure that supports face and forms a protective cavity
for brain.
• Comprised of many bones, joined by sutures.
• Bones of skull divided into those of cranium (subdivided to
skullcap(calvarium), and cranial base) and those of face.
Cranium (neurocranium)
• Formed by superior aspect of skull. It encloses and
protects brain, meninges and cerebral vasculature.
• Subdivided into a roof (calvarium), and a base:
1. Calvarium: Comprised of frontal, occipital and two
parietal bones.
2. Cranial base: Comprised of six bones –frontal, sphenoid,
ethmoid, occipital, parietal and temporal bones.
Face
• Facial skeleton
(viscerocranium) supports
soft tissues of face.
• they determine our facial
appearance.
• Consists of 14 individual
bones.
• Frontal bone, typically a
bone of calvaria, is
sometimes included as part
of facial skeleton.
Facial skeleton
•Zygomatic (2) .
•Lacrimal (2) .
•Nasal (2) .
•Inferior nasal conchae (2) .
•Palatine (2) .
•Maxilla (2) .
•Vomer .
•Mandible (jawbone) .
Cranial bones(8)
Facial bones(14)
Zygomatic (2) – Forms
cheekbones of face, and
articulates with frontal,
sphenoid, temporal and
maxilla bones.
Lacrimal (2) – smallest bones
of face.
Form part of medial wall of
orbit.
Nasal (2) – Two slender
bones, located at the bridge
of the nose.
Inferior nasal conchae (2) –
Located within nasal cavity to
increase surface area of nasal
cavity, thus increasing amount
of inspired air.
Palatine (2) – Situated superior to oral cavity, and
forms part of hard palate.
Maxilla (2) – Comprises part of the upper jaw and hard palate.
Maxillae:
 2maxillae form
upper jaw.
Below orbit,
maxilla is
perforated by
infraorbital
foramen.
Alveolar process projects downward &, with opposite side,
alveolar arch, carries upper teeth.
Vomer – Forms the posterior aspect of the nasal
septum.
Mandible (jawbone) – Articulates with base of
cranium at temporomandibular joint (TMJ).
Mandible (lower jaw)
Largest and strongest
bone of face.
• Body in midline, has a
ridge line of fusion at
symphysis menti.
Body meets ramus at
the angle of mandible
Mandible
Body :
upper border
called alveolar
part; contains 16
sockets for roots
of teeth.
Lower border
called base.
Mandible
Ramus:
vertically placed has:
 ant.coronoid process.
 post.condyloid process.
 2 processes separated by
mandibular notch.
Temporal Bone
Parts :
A. Squamous.
B. Tympanic.
C. Mastoid process.
D. Styloid process.
E. Zygomatic process.
Sutures of the Skull
• Type of fibrous joint unique to
skull.
• Immovable.
• Fuse completely around age of
20.
• Sutures are of clinical
importance, as they can be
points of potential weakness in
both childhood and adulthood.
• Main sutures in adulthood are:
• •Coronal suture.
• •Sagittal suture.
• •Lambdoid suture.
In neonates, incompletely
fused suture joints give rise to
membranous gaps between
bones, known as fontanelles.
Two major fontanelles are
frontal fontanelle (located at
junction of coronal and
sagittal sutures) and occipital
fontanelle (located at junction
of sagittal and lambdoid
sutures).
• The majority of skull fractures result from blunt force or
penetrating trauma.
• The clinical features may be obvious, such as visible injuries and
bleeding. There are also subtle signs of fracture, such as clear
fluid draining from ears and nose, poor balance and confusion,
slurred speech and a stiff neck.
Pterion:
• A ‘H-shaped’ junction
between temporal,
parietal, frontal and
sphenoid bones.
• The thinnest part of
skull.
• A fracture here can
lacerate an underlying
artery (middle meningeal
artery), resulting in a
extradural hematoma.
There are four major types of cranial fracture:
 Depressed– fracture of bone with depression of bone inwards.
They occur as a result of a direct blow, causing skull indentation,
with possible underlying brain injury.
 Linear – a simple break in bone, traversing its full
thickness. They have radiating (stellate) fracture lines away from
the point of impact. The most common type of cranial fracture.
 Basal skull– affects the base of skull. They characteristically
present with bruising behind the ears, known as Battle’s sign
(mastoid ecchymosis) or bruising around the eyes/orbits, known
as Raccoon eyes.
 Diastatic– fracture that occurs along a suture line, causing a
widening of suture. Most often seen in children.
• Facial fractures are common and
generally trauma related, i.e. road traffic
collisions, fights and falls.
• They are often associated with clinical features
such as profuse bleeding, swelling, deformity
and anaesthesia of the skin.
• The nasal bones are most frequently
fractured, due to their prominent position at
the bridge of the nose.
• A maxillofacial fracture is one that affects the
maxillae bones. This requires a trauma with a
large amount of force.
Facial fractures affecting the maxillary bones can be identified using
the Le Fort classification, depending on the bones involved, ranging
from 1 to 3 (most serious).
Bones of Head:
1. Ethmoid bone .
2. Mandible.
3. Sphenoid bone .
4. Temporal bone.
5. Nasal skeleton.
Cranial foramina:
1. Cribriform Foramina.
2. Optic Canal and Foramen.
3. Superior Orbital Fissure.
4. Foramen Rotundum.
5. Foramen Ovale.
6. Internal Acoustic Meatus.
7. Jugular Foramen.
8. Hypoglossal Canal.
9. Foramen Magnum.
10.Foramen Spinosum.
Ethmoid bone:
1. A small-unpaired bone, located in midline
of anterior cranium .
2. Term ‘ethmoid’ originates from Greek
‘ethmos’, meaning sieve. This is reflects
in its lightweight, spongy structure.
Anatomical Structure
• Situate at roof of nasal cavity, and
between two orbital cavities.
• Contributes to medial wall of orbit and
forms part of anterior cranial fossa, where
it separates nasal cavity (inferiorly) from
cranial cavity (superiorly).
• Forms a significant portion of nasal
septum and lateral nasal wall.
• Olfactory nerve (CN I) has a close
anatomical relationship with ethmoid
bone. Its numerous nerve fibers pass
through cribriform plate of ethmoid bone
to innervate nasal cavity with sense of
smell.
Ethmoid bone made up of three parts :
1. Cribriform plate.
2. Perpendicular plate.
3. Ethmoidal labyrinth.
• Cribriform plate forms roof of nasal cavity. Numerous olfactory nerve
fibers pierce it, which gives it a sieve-like structure.
• Projecting superiorly from cribriform plate is crista galli, which
provides an attachment point for falx cerebri (sheet of dura mater
that separates two cerebral hemispheres).
• Another projection of bone descends from cribriform plate
,perpendicular plate. It forms superior two-thirds of nasal septum.
Ethmoid bone made up of three parts :
• Lastly, Ethmoid bone contains two ethmoidal labyrinths. These
are large masses located at either side of perpendicular plate,
contain ethmoidal air sinuses.
Two sheets of bone form each labyrinth:
1.Orbital plate – lateral sheet of bone, which also forms medial wall
of orbit
2.Medial sheet – forms upper lateral wall of nasal cavity, from which
superior and middle conchae extend into nasal cavity.
Articulations
Ethmoid bone articulates with 13 others:
• Paired– nasal bones, maxillae, lacrimal
bones, palatine bones, inferior conchae.
• Unpaired– frontal, vomer and sphenoid
bones.
Mandible:
• Located inferiorly in facial skeleton.
• Largest and strongest bone of face.
• Forms lower jaw and acts as a receptacle for lower teeth.
• Articulates on either side with temporal bone, forming
temporomandibular joint.
Anatomical Structure
Mandible consists of a horizontal body (anteriorly) and two vertical
rami (posteriorly).
Body and rami meet on each side at angle of mandible.
Body of mandible:
1. Curved, and shaped much like a
horseshoe ,has two borders:
•Alveolar border (superior) –
contains 16 sockets to hold lower
teeth.
•Base (inferior) – site of attachment
for digastric muscle medially.
2. Marked in midline by mandibular
symphysis. The symphysis encloses
a triangular eminence –mental
protuberance, which forms shape
of chin.
3. Lateral to mental protuberance is
mental foramen (below second
premolar tooth on either side).
Rami
1. Two rami project
perpendicularly upwards from
angle of mandible.
2. Each ramus contains following
bony landmarks:
•Head – situated posteriorly,
articulates with temporal bone to
form TM joint.
•Neck – supports head of ramus,
and site of attachment of lateral
pterygoid muscle.
•Coronoid process – site of
attachment of temporalis muscle
3.Internal surface of ramus also
marked by mandibular foramen.
Foramina of mandible:
Any opening through which neurovascular structures can travel.
Mandible is marked by two foramina.
1. Mandibular foramen located on internal surface of ramus of
mandible. It serves as a conduit for inferior alveolar nerve and
inferior alveolar artery. They travel through mandibular foramen,
into mandibular canal, and exit at mental foramen.
2. Mental foramen, positioned on external surface of mandibular
body, below second premolar tooth. It allows inferior alveolar nerve
and artery to exit mandibular canal. When inferior alveolar nerve
passes through mental foramen, it becomes mental nerve
(innervates skin of lower lip and front of chin).
Muscular Attachments
Mandible serves as attachment point
for various muscles, including strong
muscles of mastication.
•Mandibular body:
O External (lateral) surface –
mentalis, buccinator, platysma,
depressor labii inferioris, depressor
anguli oris.
O Internal (medial) surface –
genioglossus, geniohyoid, mylohyoid
and digastric.
Muscular Attachments
•Mandibular rami– masseter,
temporalis, medial pterygoid and
lateral pterygoid.
Temporalis muscle attaches to
coronoid process, and masseter
attaches to rami. Lateral pterygoid
inserts into neck of mandible, and
medial pterygoid inserts into ramus
near angle of mandible.
Sphenoid bone
• Name derived from Greek
‘sphenoeides’, to mean wedge-
shaped.
Anatomical Structure
• Butterfly-shaped consists of a
body, paired greater wings and
lesser wings, and two pterygoid
processes.
Body
• Lies at center of sphenoid bone,
cubical in shape.
• Contains sphenoidal sinuses,
which separated by a septum.
• Articulates with ethmoid bone
anteriorly.
Sphenoid bone
Superior surface of sphenoid body
contains :
• Sella turcica– a saddle-shaped
depression. It has three parts:
o Tuberculum sellae– forms anterior
wall of sella turcica, and posterior
aspect of chiasmatic groove.
o Hypophyseal fossa –deepest part of
sella turcica, where pituitary gland is
located.
o Dorsum sellae– forms posterior
wall of sella turcica.
Chiasmatic groove :
• A sulcus formed by optic chiasm (where optic nerves partially
cross).
• Anterior and posterior clinoid processes surround sella turcica.
• Anterior clinoid processes arise from sphenoidal lesser wings,
while posterior clinoid processes are superolateral projections of
dorsum sellae.
• They serve as attachment points for tentorium cerebelli, a
membranous sheet that divides brain.
Greater Wing
 Extends from sphenoid body in a
lateral, superior and posterior
direction.
 Contributes to three parts of facial
skeleton:
•Floor of middle cranial fossa
•Lateral wall of skull
•Posterolateral wall of orbit
 Three foramina present in greater
wing: foramen rotundum,
foramen ovale and foramen
spinosum. They conduct maxillary
nerve, mandibular nerve and
middle meningeal vessels
respectively.
Lesser Wing
• Arises from anterior
aspect of sphenoid body
in a superolateral
direction.
• Separates anterior cranial
fossa from middle cranial
fossa.
• It also forms lateral
border of optic canal –
through which optic
nerve and ophthalmic
artery travel to reach
eye.
• Body of sphenoid forms medial border of optic canal.
• There is a ‘slit-like’ gap between lesser and greater wings of
sphenoid (superior orbital fissure).
Pterygoid Process
• Descends inferiorly from point of junction between sphenoid body
and greater wing.
• It consists of two parts:
1. Medial pterygoid plate – supports posterior opening of nasal
cavity.
2. Lateral pterygoid plate – site of origin of medial and lateral
pterygoid muscles
Muscular Attachments
• Lateral and medial
pterygoid muscles, which
form some of muscles of
mastication, originate from
lateral pterygoid plate of
sphenoid bone.
Articulations
It has articulations with twelve
other bones:
•Unpaired bones – Occipital,
vomer, ethmoid and frontal
bones.
•Paired bones – Temporal,
parietal, zygomatic and
palatine bones.
Temporal bone
• Contributes to lower lateral walls of
skull.
• Contain middle and inner portions of
ear, and crossed by majority of cranial
nerves.
• Lower portion of bone articulates with
mandible, forming TMJ.
Anatomical Structure
• Comprised of five constituent parts.
• Squamous, Tympanic and petromastoid
parts make up majority of bone, with
zygomatic and styloid processes
projecting outwards.
Parts of temporal bone in more detail.
Squamous
• Also known as squama temporalis,
largest part of temporal bone.
• It is flat and plate-like, located
superiorly.
• Outer facing surface of squamous
bone is convex in shape, forming
part of temporal fossa.
• Lower part of squamous bone is site
of origin of temporalis muscle
• Bone articulates with sphenoid
bone anteriorly, and parietal bone
laterally.
Zygomatic Process
• Arises from lower part of squama temporalis.
• Projects anteriorly, articulating with temporal process of zygomatic
bone , form zygomatic arch (palpable as ‘cheek bones’).
• Zygomatic processes forms articular tubercle –anterior boundary of
mandibular fossa, part of TMJ.
• Masseter muscles attaches to lateral surface of zygomatic process.
Tympanic
• Lies inferiorly to squamous, and anteriorly to petromastoid part.
• Surrounds external auditory opening, leads into external auditory
meatus of external ear.
Styloid Process
Located immediately underneath opening to auditory meatus.
Acts as an attachment point for muscles and ligaments, such as
Stylomandibular ligament of TMJ.
Petromastoid
• Located posteriorly.
• Split into mastoid and petrous
parts.
• On a lateral view of temporal
bone, only mastoid part is
visible.
Mastoid process:
• An inferior projection of bone,
palpable just behind ear.
• It is a site of attachment for
many muscles, such as
sternocleidomastoid.
• Also of clinical importance are
mastoid air cells.
Mastoid process:
1. These hollowed out areas within
temporal bone.
2. They act as a reservoir of air,
equalizing pressure within
middle ear in case of auditory
tube dysfunction.
3. Mastoid air cells might be
infected, known as mastoiditis.
Petrous part is pyramidal shaped,
and lies at base of temporal bone.
It contains inner ear.
Muscular Attachments of temporal bone
Muscle Site of Attachment Description
Temporalis Originates from the
Muscle of mastication
lower part of squamous
Masseter Lateral zygomatic
Muscle of mastication
surface
Sternocleidomastoid Mastoid process Superficial muscle of the neck. Involved in
rotation of head and flexion of neck.
Important landmark for
the anterior and posterior cervical
triangles.
Posterior belly of digastric Mastoid process A suprahyoid muscle. Involved in processes
such as swallowing.
Articulations of temporal bone:
• A major articulation of temporal bone is with mandible to form TMJ.
• Squamous part articulates with sphenoid bone anteriorly and
parietal bone laterally.
• Zygomatic process articulates with zygomatic bone to form
zygomatic arch (i.e. cheekbones).
Nasal skeleton :
Combination of bone and cartilage,
both form external nose and
internal nasal septum.
Anatomical Structure
• Skeleton of nose is formed by
three types of tissue; bone,
cartilage and fibro-fatty tissue.
• Scaffolding of nose is divide into
two parts; external nasal
skeleton and internal nasal
septum.
External Nasal skeleton
• Extends nasal cavities onto front of face.
• Partly formed by nasal and maxillary bones, situated superiorly.
• Inferior portion of nose made up of hyaline cartilages; lateral, major alar, minor
alar, and cartilaginous septum.
• Lateral and major alar cartilages are largest, and contribute most to shape of
nose here.
• Minor alar cartilages vary in number; there are usually 3 or 4 on each side.
Internal Nasal Septum
• Separates nasal cavity into two nostrils.
• Bones contribute to nasal septum divided into:
1. Paired bones: Nasal, maxillary and palatine bones
2. Unpaired bones: Ethmoid and vomer bones.
Internal Nasal Septum
In addition to bones of nose, septal and
greater alar cartilages also constitute part
of nasal septum.
• Ethmoid contributes to central portion
of nasal septum. It is one of the most
complex bones in the human body.
• Anterior and posterior parts formed by
the septal cartilage and vomer bone
respectively.
• Floor of nasal cavity formed by hard
palate, separating it from oral cavity.
• Hard palate consists of palatine bone
posteriorly, and palatine process of
maxilla anteriorly.
• Cribriform plate of ethmoid bone forms
posterior roof.
A foramen (pl. foramina):
• An opening that allows passage
of structures from one region to
another.
• In skull base, referred to as
cranial foramina.
Cranial Nerve Foramina:
Cribriform Foramina
• Numerous perforations in cribriform
plate of ethmoid bone. Connect
anterior cranial fossa with nasal cavity.
• Allow passage of axons of olfactory
nerve from olfactory epithelium of
nose into anterior cranial fossa where
they communicate with olfactory bulb.
Optic Canal and Foramen
• Optic canal permits passage of optic
nerve (CN II) and ophthalmic artery
into bony orbit.
• Bounded medially by body of sphenoid,
laterally by lesser wing .
Superior Orbital Fissure
• A cleft that opens anteriorly into orbit.
• Bordered superiorly by lesser wing and
inferiorly by greater wing .
• Transmits several structures that listed
below (from superior to inferior):
1. Lacrimal nerve.
2. Frontal nerve – branch of ophthalmic
nerve of trigeminal nerve (CN V).
3. Superior ophthalmic vein.
4. Trochlear nerve (CN IV)..
5. Superior division of Oculomotor nerve (CN
III).
6. Nasociliary nerve – branch of ophthalmic
nerve of trigeminal nerve (CN V).
7. Inferior division of Oculomotor nerve (CN
III).
8. Abducens nerve (CN VI).
9. A branch of Inferior ophthalmic vein.
Foramen Rotundum
• Located at base of greater wing, inferior to superior orbital fissure.
• Provides a connection between middle cranial fossa and
pterygopalatine fossa.
• Maxillary nerve (branch of trigeminal nerve, CN V) passes through
this foramen.
Foramen Ovale
• Located at base of greater wing of sphenoid.
• Posterolaterally to foramen rotundum within middle cranial fossa.
• Conducts mandibular nerve (branch of trigeminal nerve, CN V) and
accessory meningeal artery.
Foramen Spinosum
• Located within middle cranial fossa, laterally to foramen ovale.
• Allows passage of middle meningeal artery, middle meningeal vein
and meningeal branch of CN V3.
Internal Acoustic Meatus
• Bony passage located within
petrous part of temporal bone.
• Connects posterior cranial fossa
and inner ear.
• Transporting neurovascular
structures to the auditory and
vestibular apparatus.
• Facial and vestibulocochlear
nerves pass through internal
acoustic meatus, alongside
vestibular ganglion and
labyrinthine artery.
Jugular Foramen
• Formed anteriorly by petrous part of
temporal bone and posteriorly by
occipital bone.
• Considered as three separate
compartments with their respective
contents:
1. Anterior – contains inferior petrosal
sinus (a Dural venous sinus).
2. Middle – transmits glossopharyngeal
nerve, vagus nerve and cranial part of
accessory nerve.
3. Posterior – contains sigmoid sinus, and
transmits meningeal branches of occipital
and ascending pharyngeal arteries.
Hypoglossal Canal
Located in occipital bone,
hypoglossal nerve (CN XII) passes
to exit posterior cranial fossa.
Foramen Magnum
• Largest of cranial foramina.
• Lies in occipital bone within
posterior cranial fossa, and
allows passage of medulla and
meninges, vertebral arteries,
anterior and posterior spinal
arteries and dural veins.
• Spinal division of accessory
nerve ascends through foramen
magnum to join cranial division.
Once combined, completed
nerve exits through jugular
foramen .