Download BONES OF SKULL

Muhammad Sohaib Shahid
(Lecturer & Course Co-ordinator MID)
University Institute of Radiological Sciences &
Medical Imaging Technology (UIRSMIT)
*
* Skull
* The bones
of the skull can be divided into two categories,
those that form the vault or cranium and enclose the brain,
and those which form the framework of the face.
* Cranial bones
There are 8 cranial bones which form a case to protect and
contain the brain;
Bone
Frontal bone
Parietal bones
Occipital bone
No. of
Bones
Description
1
•The frontal bone is a single convex bone extending
from the orbits to the coronal suture behind.
•It forms the forehead and the roof of the orbits.
2
1
•The two parietal bones form the bulk of the vault of
the skull behind the frontal bone.
•Each bone is quadrilateral in shape and articulates
with the frontal, occipital, temporal and sphenoid
bones as well as with each other.
•The occipital bone forms the back and base of the
skull.
•It is divided into squamous, lateral and basilar parts.
Occipital bone
Temporal bone
1
•The occipital bone forms the back and base of the skull.
•It is divided into squamous, lateral and basilar parts.
2
•Each temporal bone contributes to the base and to the lower
lateral aspect of the skull.
•It is divided into squamous, petrous, mastoid and tympanic
parts.
•The squamous part is thin, translucent and forms the anterior
and upper part of the bone.
•The petrous part is the solid, wedge of bone that forms most of
the posterior and inferior portions of the temporal bone.
•The mastoid part of the temporal bone lies below the
squamous part and behind the tympanic part.
•The tympanic part of the temporal bone surrounds the
external auditory meatus.
Ethmoid bone
Sphenoid bone
1
•The Ethmoid is a single mid line bone which forms parts of
the nasal septum, medial wall of the orbital cavity and the
roof and lateral wall of the nose.
1
•This single bone is found in the base of the skull and is often
described as being butterfly-shaped as it consists of a central
body and three paired processes.
* Facial bones
* These 14 bones do not contribute to the cranial cavity,
but form the structure of the face;
Bone
Maxilla
Number
of
Description
bones
2
Important Landmarks
•Alveolar process - extends inferiorly from the
•The paired
body of the maxilla and supports the teeth within
maxillary
bony sockets.
bones support •Zygomatic process - projects laterally from the
the teeth of
body and articulates with the Zygomatic bone.
the upper jaw •Palatine process - extends horizontally to form
and contribute most of the hard palate.
to much of the •Maxillary sinuses - are the largest of the
skeleton of the paranasal sinuses and are situated in the bodies
upper face.
of the maxillary bones. It communicates with the
nasal cavity through the maxillary hiatus.
Bone
Zygomatic
bones
Mandible
Number
of bones
Description
Important Landmarks
•Frontal process - forms outer margin
of the orbit by articulating with the
Zygomatic process of the frontal bone.
•Temporal process - forms the
prominent
Zygomatic
arch
by
articulating with the Zygomatic
process of the temporal bone.
2
•The two zygomatic
bones form the
skeleton of the
cheeks and the
inferior and lateral
walls of the orbit.
1
•Body - an arch that forms the main
bulk of the mandible.
•Alveolar ridge - forms the superior
margin of the body of the mandible
•The mandible is the
and houses the lower teeth.
only movable bone
•Rami - these are the flat vertical
in the skull.
projects that ascend from the obtuse
•It consists of a
angle of the body.
horizontal,
•Coronoid - found on the top of the
horseshoe-shaped
ramus it lies anteriorly and serves as
body and two
an attachment point for temporalis.
vertical rami.
•Condylar processes - found on the
top of the ramus it lies posteriorly and
articulates with the temporal bone at
the temporomandibular joint (TMJ).
Bone
Palatine
bones
Hyoid bone
Number
of
bones
2
1
Description
Important Landmarks
•Horizontal plate - forms the
posterior portion of the hard palate.
•The palatine bone forms •Perpendicular plate - the medial
part of the hard palate, the surface forms the lateral wall of the
floor and lateral wall of the nasal cavity and articulates with the
nasal cavity and the floor inferior nasal concha.
of the orbit.
•Orbital process - projecting from
the perpendicular plate it forms the
posterior part of the orbital floor.
•The horseshoe-shaped
hyoid bone is situated in
the upper part of the front
of the neck, at the level of
C3.
•It does not articulate with
any bones but is
maintained in position by
the muscles, ligaments and
membranes attaching to it.
•It gives attachment to the
•Body - the curved medial portion of
the bone.
•Lesser cornu - two small superior
projections from the junction
between the body and the greater
cornu.
•Greater cornu - two backward
projections from the body.
Lacrimal bones
Nasal bones
Vomer
•The paired Lacrimal bones are
small, thin and rectangular, and
each lie in the anterior part of
the medial wall of the orbit.
•They house the Lacrimal sac
which collects tears from the
eyes via the nasolacrimal duct
and empties them into the nasal
cavity.
•Lacrimal fossa - a
depression that houses
the Lacrimal sac.
2
•The two nasal bones form the
upper part of the bridge of the
nose.
•Superior border articulates with the
frontal bone.
•Inferior border - is
continuous with the
lateral nasal cartilage.
1
•Alae - a wing like
projection which
•The vomer is a flat bone which
articulates with the
forms the lower part of the septum sphenoid bone.
of the nose.
•Anteriorly it articulates
with the septal
cartilage.
2