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Osteology
Skull
Foramina
Cavities
joints
Surface markings
The cervical vertebrae
BAAB 16/05/2016
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The head skeleton is formed of the skull
The neck skeleton is formed of the cervical
vertebrae of the vertebral column.
SKULL:
The skull is a bony structure that forms the
skeleton of the head in most vertebrates.
◦ Therefore, a human skull is the bony structure
whose bones are forming through
intramembranous ossification that forms the head
in the human skeleton
◦ It supports the structures of the face and forms a
cavity for the brain; Like the skulls of other
vertebrates, it protects the brain from injury.
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The skull consists of two parts
there of different embryological origin
◦ the neurocranium (or braincase) forms the protective
cranial cavity that surrounds and houses the brain and
brainstem. This is also subdivided into skullcap or
cranial roof known as calvarium, and the cranial base.
◦ The facial skeleton (viscerocranium) is formed by the
bones supporting the face including the mandible.
Except for the mandible, all other bones of the
skull are joined together by sutures—synostosis
(synarthrodial or immovable) joints formed by
bony ossification, with Sharpey's fibres
permitting some flexibility.
Sometimes there can be extra bone pieces within
the suture known as wormian bones or sutural
bones.
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The mandible forms a temporomandibular synovial
double condylar variety.
Cranial skull:
◦ The cranium (also known as the neurocranium), is formed by
the superior aspect of the skull. It encloses and protects the
brain, meninges and cerebral vasculature.
◦ Anatomically, the cranium can be subdivided into a roof (known
as the calvarium), and a base.
◦ Calvarium: Comprised of the frontal, occipital and two parietal
bones.
◦ Cranial base: Comprised of six bones – the frontal, sphenoid,
ethmoid, occipital, parietal and temporal bones. The base
provides an articulation point for the 1st cervical vertebra
(atlas), as well as the facial bones and the mandible (jaw bone).
◦ The base is divided into anterior, middle and posterior cranial
fossae.
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Facial skeleton:
◦ also known as the viscerocranium supports the soft
tissues of the face. In essence, they determine our
facial appearance.
◦ It consists of 14 individual bones, which fuse to
house the orbits of the eyes, tympanocochlea
apparatus, nasal and oral cavities, as well as the
sinuses.
◦ The frontal bone, typically a bone of the calvaria, is
sometimes included as part of the facial skeleton.
◦ The facial bones are:
◦ Zygomatic (2) – Forms the cheek bones of the face,
and articulates with the frontal, sphenoid, temporal
and maxilla bones.
◦ Lacrimal (2) – The smallest bones of the face. They
form part of the medial wall of the orbit.
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Nasal (2) – Two slender bones, located at the
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Inferior nasal conchae (2) – Located within the
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bridge of the nose.
nasal cavity, they increase the surface area of the
nasal cavity, thus increasing the amount of inspired
air that contact with the nasal cavity walls.
Palatine (2) – Situated at the rear roof of oral cavity,
and forms part of the hard palate.
Maxilla (2) – Comprises part of the upper jaw and
hard palate.
Vomer – Forms the posterior aspect of the nasal
septum.
Mandible (jaw bone) – Articulates with the base of
the cranium at the temporomandibular joint (TMJ).
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JOINTS OF THE SKULL:
◦ Joints of the skull are mostly the suture variety of
fibrous joint.
◦ They are immovable, and fuse completely around the
age of 20.
Fig – The major fontanelles and sutures of the skull
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Sutures are of clinical importance, as they can be
points of potential weakness in both childhood
and adulthood.
◦ The main sutures in adulthood are:
 Coronal suture which fuses the frontal bone with the
two parietal bones.
 Sagittal suture which fuses both parietal bones to
each other.
 Lambdoid suture which fuses the occipital bone to
the two parietal bones.
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In neonates, the incompletely fused suture
joints give rise to membranous gaps between
the bones, known as fontanelles. The two major
fontanelles are the frontal fontanelle (located at
the junction of the coronal and sagittal sutures)
and the occipital fontanelle (located at the
junction of the sagittal and lambdoid sutures)
Others (minor) are sphenoidal fontanelles
(located at the junction of the suture between
frontal, parietal, sphenoidal and zygomatic
bones. This is a future pterion) and the mastoid
fontanelle (located at the junction of the suture
of temporal, parietal and occipital bones)
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Skull injury and fracture:
The majority of skull fractures result from blunt
force or penetrating trauma, and can produce
numerous signs and symptoms.
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 the ears and nose
(cerebrospinal fluid leak indicative of base of
skull fracture), poor balance and confusion,
slurred speech and a stiff neck.
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There are certain areas of the skull that are natural
points of weakness:
The pterion: a ‘H-shaped’ junction between
temporal, parietal, frontal and sphenoid bones. The
thinnest part of the skull. A fracture here can
lacerate an underlying artery (the middle meningeal
artery), resulting in a extradural haematoma.
Anterior cranial fossa: Depression of skull formed
by frontal, ethmoid and sphenoid bones.
Middle cranial fossa: Depression formed by
sphenoid, temporal and parietal bones.
Posterior cranial fossa: Depression formed by
squamous and mastoid temporal bone, plus
occipital bone.
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There are four major types of cranial fracture:
◦ Depressed – A fracture of the bone with depression
of the bone inwards. They occur as a result of a
direct blow, causing skull indentation, with possible
underlying brain injury.
◦ Linear – The simple break in the 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 the 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
eye’s.
◦ Diastatic – A fracture that occurs along a suture line,
causing a widening of the suture. They are most
often seen in children.
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Fig - Skull showing depressed fracture of the frontal bone, a linear fracture marked A
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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).
 A Le Fort fracture of the skull
Classification and external resources
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LeFort I (red), II (blue), and III (green) fractures
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ANATOMICAL LAND MARKS:
These are on the outer and inner surfaces of the
skull.
The point at which the frontal bone and the two
parietal bones meet is known as "Bregma“
The point at which the two parietal and occipital
bones meet is known as "Lambda".
these landmarks indicate the fontanelle in
newborns, also act as reference points in
medicine and surgery.
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The inner surface of the skull-cap is concave and
presents depressions for the convolutions of the
cerebrum,
numerous furrows for the lodgement of branches of
the meningeal vessels.
a middle line is a longitudinal groove, narrow in
front, where it commences at the frontal crest, but
broader behind; it lodges the superior sagittal sinus,
and its margins afford attachment to the falx
cerebri.
A groove is crossed in front by the coronal suture
and behind by the lambdoid suture, while the
sagittal suture lies in the medial plane between the
parietal bones.
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FORAMINA:
The foramen magnum (Latin: great hole) is a
large oval opening in the occipital bone.
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It is one of the several oval or circular
openings (foramina) in the base of the skul
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The spinal cord, an extension of the medulla,
passes through the foramen magnum as it
exits the cranial cavity
Also other structures pass through. These are
the vertebral arteries, the anterior and
posterior spinal arteries, the tectorial
membranes and alar ligaments.
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Other foramina, bones and contents are:
BONE
Frontal
Frontal
Ethmoid
FOSSA
Anterior
cranial
-
FORAMEN
VESSELS
NERVE
supraorbital
Supraorbital
supraorbital
Foramen
caecum
emmissary
Cribriform
plate
-
Olfactory
nerve bundle
Ethmoid
Anterior
cranial
Anterior
ethimoid
Anterior
ethimoid
Anterior
ethimoid
Ethmoid
Anterior
cranial
Posterior
ethimoid
Posterior
ethimoid
Posterior
ethimoid
Sphenoidal
Sphenoidal
Middle
cranial
Optical canal
-
Optic nerve II
Sup. Orbital
fissure
Sup. and inf.
orbital veins
Oculomotor,
Trochlea,
Ophthalmic
and
Abducent
sphenoid
Foramen
rotundum
maxillary
Maxilla
-
sphenopalatine nasopalatine
Incisive
foramen/canal
palatine
-
Greater
palatine
Greater
palatines
Greater
palatine
Palatine and
maxilla
-
Lesser
palatine
Lesser
palatines
Lesser
palatine
Sphenoid and
maxilla
-
Inf. Orbital
fissure
Inf.
Ophthalmic vv
infraorbitals
Zygomatic,
infraorbital of
maxillary n.
orbital
branches of
pterygopalatine
maxilla
-
infraorbital
infraorbitals
infraorbital
Sphenoidal
Middle cranial
Foramen ovale accessory
meningeal aa.
Mandibular,
lesser petrosal
Sphenoidal
Middle cranial
Foramen
rotundum
Meningeal br.
of mandibular
Middle
meningeal aa
Sphenoid
Middle cranial
Foramen
lacerum
Internal
carotid aa,
artery of
pterygoid
canal
Nerve of
pterygoid
canal
Temporal
Middle cranial
Internal
acoustic
meatus
Labyrinthine
aa.
Facial and
vestibulocochlear
Temporal
Posterior
cranial
Jugular
Inf. Petrosal
sinus and
sigmoid sinus
Glossopharyn
geal, vagus
and accessory
occipital
Posterior
cranial
hypoglossal
-
hypoglossal
Occipital
Posterior
cranial
Foramen
magnum
Ant. And post. Medulla
Spinal aa. and oblongata
vertebral aa.
Temporal
Posterior
cranial
stylomastoid
Stylomastoid
artery
Facial
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The opisthion is the midpoint on the
posterior margin of the foramen magnum and
is a cephalometric landmark.
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Another landmark is the basion located at the
midpoint on the anterior margin of the
foramen magnum.
The foramen magnum is a very important
feature in bipedal mammals. Studies on the
foramen magnum position have shown a
connection to the functional influences of
both posture and locomotion.
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Opisthion shown in red
Basion shown in red
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Superior orbital fissure;
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List the contents:
◦ superior and inferior divisions of oculomotor nerve (III)
◦ trochlear nerve (IV)
◦ lacrimal, frontal and nasociliary branches of ophthalmic
nerve (V1)
◦ abducens nerve (VI)
◦ superior and inferior divisions of ophthalmic vein. Inferior
division also passes through the inferior orbital fissure.
◦ sympathetic fibers from cavernous plexus
Skull basal cranial fossae
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Anterior cranial fossa:
Anterior limit by the posterior wall of the
frontal sinus.
Posterior limit by the anterior clinoid processes
and the planum sphenoidale formed by the
roof of the sphenoid sinus.
lateral boundaries by the frontal bone.The
frontal bone houses the supraorbital foramina,
which, along with the frontal sinuses, form 2
important surgical landmarks during
approaches involving the anterior skull base.
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Middle cranial fossa:
The anterior limit by the greater wing of the
sphenoid
The posterior limit is the clivus.
The lateral limit by the greater wing of the
sphenoid as it extends laterally and upward from
the sphenoid body to meet the squamous portion
of the temporal bone and the anteroinferior
portion of the parietal bone.
◦ The greater wing of the sphenoid forms the anterior
floor of the fossa.
◦ The anterior aspect of the petrous temporal bone forms
the posterior floor of the middle cranial fossa.
◦ The body of the sphenoid makes up the central portion
of the middle fossa and houses the sella turcica.
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Posterior cranial fossa:
The posterior skull base consists of primarily the occipital
bone, with contributions from the sphenoid and temporal
bones.
The anterior portion by the basal portion of the occipital
bone (the basiocciput) and the basisphenoid. These 2
regions combine to form the midline clivus.
The lateral wall by the posterior surface of the petrous
temporal bone and the lateral aspect of the occipital bone.
The occipital bone also fuses with the mastoid portion of
the temporal bone to form the occipitomastoid suture.
The petrous portion of the temporal bone and the greater
wings of the sphenoid bone are particularly important for
identifying structures. The overlying tentorium cerebelli
separates the cerebellum from the cerebral hemispheres
above, whereas the occipital bone form the lateral walls
and floor.
 Vertebral
column in general
◦ The vertebral column usually consists of 33 vertebrae:
24 presacral vertebrae (7 cervical, 12 thoracic, and 5
lumbar) followed by the sacrum (5 fused sacral
vertebrae) and the coccyx (4 frequently fused
coccygeal vertebrae).
◦ The adult vertebral column presents four
anteroposterior curvatures: thoracic and sacral, both
concave anteriorly, and cervical and lumbar, both
concave posteriorly.
Fig: The vertebral column indicating the curvetures
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Parts of a Vertebra.
◦ A typical vertebra consists of (1) a body and (2) a
vertebral arch, which has several processes (articular,
transverse, and spinous) for articular and muscular
attachments.
◦ Between the body and the arch is the vertebral
foramen
◦ the sum of the vertebral foramina constitutes the
vertebral canal, which houses the spinal cord
◦ Between the vertebrae of the spine are thin regions of
cartilage known as the intervertebral discs.
◦ Intervertebral discs are made of an outer shell known
as the annulus fibrosus (bone binder) and a soft,
pulpy region known as the nucleus pulposus (shock
absorber) in the middle.
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The body is the main weight-bearing region of a
vertebra, making up the bulk of the bone’s mass.
Extending from the body, the transverse processes are
thin columns of bone that point out to the left and right
sides of the body.
The spinous process extends from the ends of the
transverse processes in the posterior direction.
Between the body, transverse processes and spinous
process is the vertebral foramen, a hollow space that
contains the spinal cord and meninges.
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The bars joining a body to the transverse process are
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The bars joining the transverse processes and
continuous backward to spinous processes are laminae.
pedicles.
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Features of a typical vertebral bone
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Cervical Vertebrae, the skeleton of the neck
The seven vertebrae of the neck are
characterized by an opening in each transverse
process known as a foramen transversarium.
The upper six pairs of foramina transversaria
transmit the vertebral artery.
The C1 vertebra, which supports the skull, is
termed the atlas after the Greek titan who held
the Earth on his shoulders.
The C2, which serves as a pivot for the atlas
when moving up and down, is termed the axis.
The C1, which has neither body nor spinous
process, consists of two lateral masses
connected by a short anterior and a longer
posterior arch.
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Fig: An atlas
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The C2, (axis) is characterized by the dens (or odontoid
process), which projects upward from the body and
articulates with the anterior arch of the atlas.
The lower cervical vertebrae, C2 to 6 are typical and
present short, bifid spinous processes.
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Each transverse process, pierced by a foramen transversarium,
The anterior tubercles of C6 vertebra are large and are
termed the carotid tubercles, because the common
carotid arteries can be compressed against them.
C7 vertebra has a long, non-bifid spinous process and
is known as the vertebra prominens. The anterior
tubercles (costal processes) of C7 vertebra may develop
separately as cervical ribs. (Lumbar ribs are less
frequent.)
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Questions and answers
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Which curvatures first appear in the vertebral column?
◦ The thoracic and sacral curvatures are primary appearing during
embryonic period, while the cervical and lumbar curvatures are
secondary and appear during foetal period and accentuated in
infancy period
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Where are the intervertebral foramina and what do they contain?
◦ In between the adjacent pedicles and typically each contains a spinal
ganglion and a ventral root (rootlets) of a spinal nerve
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What are the key features of the cervical, thoracic, lumbar, and
sacral vertebrae?
◦ Are respective foramina tranversaria, articulation with the ribs,
absence of the mentioned features and fussion