The Skull

Dr. Sandeth Phan

 skull
• The skull is composed of 22 bones, which may be divided
into the cerebral cranium and facial cranium

• Cerebral cranium (8) ―larger, upper and posterior part,

contains and protects the brain
– Single bones: include
frontal bone
ethmoid bone
sphenoid bone
occipital bone
– Paired bones: include
temporal bone
parietal bone
 BONES OF CALVARIUM
PARIETAL
(2)

FRONTAL
(1)

SPHENOID
(1)

OCCIPITAL
(1)
TEMPORAL
(2)
• Bones of facial cranium (14) ―smaller, lower, and anterior
part, contains bones that surrounded
the eye, nose and mouth
– Single bones: include
mandible
vomer
– Paired bones: include
maxilla
nasal bone
lacrimal bone
palatine bone
zygomatic bone
inferior nasal concha
• Sutures
– Sagittal
– Coronal (frontal)
– Lambdoidal
– Squamosal
Sagittal suture
Coronal Suture
Lambdoidal Suture
Squamosal Suture
 LANDMARKS AND BONES
1. FRONT OF SKULL
FRONTAL BONE
(1)

NASAL BONES
(2)
ORBIT
ZYGOMATIC BONE
EYE
(2) FORMS CHEEK
SOCKET
NASAL
APERTURE MAXILLARY BONE (2)-
ALVEOLAR PROCESS
FOR UPPER TEETH
MANDIBLE(1)-
ALVEOLAR PROCESS
FOR LOWER TEETH
 parietal
bone

Frontal bone Sphenoid

bone

Temporal
bone
Zygomatic bone
Occipital
bone
Nasal bone

Maxilla

Mandible
 SKULL INDIVIDUAL BONES
• FRONTAL BONE:-
• The large bone that makes up the forehead and supplies the
upper edge and roof of the orbit (eye socket).
• The frontal bone articulates (comes together) with a number
of other bones including the parietal, nasal, ethmoid,
maxillary, and zygomatic bones.

• 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.
PARIETAL BONES
• The main bone on the side of the skull.
• The word "parietal" comes from the Latin
"parietalis" meaning "belonging to the wall."
• It articulates (joins) with the other parietal
bone in the midline (top of the head), with the
frontal bone in front of it, with the occipital
bone behind it, and with the sphenoid and
temporal bones lower down on the side of the
skull.
OCCIPITAL BONE
• From the Latin, meaning the part of the head opposite the
front.
• The bone that forms the rear and the rear bottom of the skull.
• The occipital bone articulates (joins) with the parietal and
temporal bones of the skull, the sphenoid bone in front of it,
and the first cervical vertebra (the atlas) beneath it
• 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
TEMPORAL BONE
• A large irregular bone situated at the base and side of the skull. The
temporal bone is connected with the mandible (the jaw bone) via the
temporomandibular (TM) joint.
• The temporal bone is formed of three parts (squamous, tympanic
and petrous) that are distinct at birth but then fuse. The petrous
portion of the temporal bone contains the structures of the inner ear.
• Landmarks:
– 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.
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.
• The Greek physician Galan wrote that the sphenoid bone was "like a
wedge thrust between the skull and the superior maxilla."
• 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.
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
– Cribiform plate: forms the roof of the nasal cavity
– Olfactory foramina: small holes within the cribiform plate for
passage of the first cranial nerve (for smell)
– Crista galli: upward extension of bone above the cribiform plate,
acts as an anchoring point for one of the coverings of the brain.
– Nasal concha (turbinates): two scroll-shaped projections with a
mucus membrane on either side of the nasal septum. Function
to cause air turbulence and trap inhaled particles.
MAXILLARY BONES

41
• The largest bones of the face, except for 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 roof of the mouth, the floor and lateral wall of
the nose, and the floor of the orbit.
• 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.
Maxilla (Anterior View) (Yellow Colored Bones)

45
 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
46
Nasal Bones (Anterior View) (Bridge of the nose, below frontal bone)

47
 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. 48
Zygomatic Bones (Anterior View) (Pink Colored Bones)

51
 Mandible

Largest and strongest

bone of the face.

Forms the lower jaw and

holds the lower teeth in
place.

The mandible consists of

a curved, horizontal
portion, the body, and two
perpendicular portions,
the rami, which unite with
the ends of the body
nearly
at right angles. 52
• Largest and strongest bone of the face.
• Forms the lower jaw and holds the lower teeth in place.
• Landmarks:
– Body: curved horizontal portion of the mandible
– Rami: two upward projections of bone that are perpendicular to the
body of the mandible.
– Angle of the mandible: angle formed where the body meets the
ramus
– Condylar process: a condyle on the posterior portion of the ramus
that articulates with the mandibular fossa of the temporal bone.
– Coronoid process: a sharp projection of bone on the anterior portion
of the ramus that acts as a point of muscle attachment.
– Alveolar process: arch of bone containing the lower teeth
– Mental foramen: small hole on the side of the body for blood vessels
and nerves.

54
Mandible (Anterior View) (Lower Jaw)

55
Mandible (Lateral View) (Lower Jaw)

56
 Palatine bone :-

It contributes to the
walls of three
cavities: the floor
and lateral wall of
the nasal cavity,
the roof of the
mouth, and the
floor of the orbit
LACRIMAL BONE
Smallest and most
fragile bone of the
face, is situated at
the front part of
the
Medial of the
orbit.

Contains the
lacrimal
sac and the naso-
lacrimal duct.
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
VOMER :-
One of the unpaired
facial bones of the
skull.

Located in
the midsagittal line,
and touches the
sphenoid, the
ethmoid, the left and
right palatine bones,
and the left and right
maxillary bones.
END!