SKULL ( NORMA LATERALIS )

SKULL
( NORMA LATERALIS )
LEARNING OBJECTIVES
At the end of lecture students should be able to know,
• Cranial and facial subdivision.
• Temporal bone.
• Mastoid process and styloid process.
• Zygomatic bone,
• Parietal bone.
• Maxillary Bone
• Mandible
• Temporal fossa
• Infratemporal fossa
• The zygomatic arch
• External acoustic meatus
• Suprameatal triangle
• Asterion
• Pterion
• Infantile Skull with Fontanelles
BONES SEEN IN NORMA LATERALIS
1. Frontal
2. Parietal
3. Occipital
4. Temporal
5. Sphenoid
6. Zygomatic
7. Mandible
8. Maxilla
9. Nasal
CRANIAL AND FACIAL SUBDIVISIONS
Temporal
Bone
 Form the
inferolateral aspects of the skull and parts of
cranial floor
 Divided into Five major regions – squamous,
tympanic, mastoid, and petrous, styloid process
 Major markings include the zygomatic, styloid, and
mastoid processes, and the mandibular and middle
cranial fossae
 Major openings include the stylomastoid and
jugular foramina, the external and internal
auditory meatuses, and the carotid canal
MASTOID PROCESS AND STYLOID
PROCESS
 Mastoid process is a large projection
from the lower part of the mastoid
temporal bone, posterio- inferior to the external acoustic meatus.
 Styloid process is a thin long projection from the norma basalis ( anteriomedial to the mastoid process) it is directed downwards, forwards and
slightly medially.
Mastoid temporal bone
 Mastoid part of the temporal bone lies just behind the external acoustic
meatus.
 Continuous anterio-superiorly with the squamous temporal bone.
 The mastoid temporal bone articulates
 Posteriosuperiorly with the posterio -inferior part of the parietal bone
at the horizontal parieto-mastoid suture.
 Posteriorly with the aquamous occipital bone at the occipitomastoid
suture.
ZYGOMATIC BONE
 The zygomatic bone is small and
quadrangular, and is situated at the
upper and lateral part of the face
 It presents a malar and a temporal
surface
 4 processes,
 frontosphenoidal
 orbital
 Maxillary
 Temporal
 4 borders.
PARIETAL BONE
 The parietal bones form, by their
union, the sides and roof of the
cranium.
 Each bone is irregularly quadrilateral in form
 It Has
 2 surfaces
 four borders
 four angles.
PARIETAL BONES AND
MAJOR ASSOCIATED
SUTURES
 Four sutures mark the
articulations of the parietal
bones
 Coronal suture – articulation
between parietal bones and
frontal bone anteriorly
 Sagittal suture – where right
and left parietal bones meet
superiorly
 Lambdoid suture – where
parietal bones meet the
occipital bone posteriorly
 Squamosal or squamous suture – where parietal and temporal bones
meet
MAXILLARY BONE
 The maxillæ are the largest bones of the face, excepting the mandible,
and form, by their union, the whole of the upper jaw
 Each bone consists of a body and four processes—zygomatic, frontal,
alveolar, and palatine
MANDIBLE
 The mandible, the largest and
strongest bone of the face, serves
for the reception of the lower
teeth
 It consists of
 A curved, horizontal portion,
body
 Two perpendicular portions,
the rami, which unite with the
ends of the body nearly at
right angles.
Temporal fossa
 Temporal fossa
Boundaries
 (a). Above, by the temporal line of the
frontal bone.
 (b). Below, by the upper border of the zygomatic arch laterally, and by
the infratemporal crest of the greater wing of the sphenoid bone
medially.
 Through the gap deep to the zygomatic arch, the temporal fossa
communicates with the infratemporal fossa.
INFRATEMPORAL FOSSA






The infratemporal fossa is an irregularly shaped cavity, situated below
and medial to the zygomatic arch.
Boundaries.
(a).Roof is formed medially by the
infratemporal surface of the greater
wing of the sphenoid and small part
of the squamous temporal bone.
(b). Floor is open.
(c ). Medial wall is formed by the
lateral plate and the pyramidal
process of the palatine bone.
(d). Lateral wall is formed by the
ramus of the mandible.
The foramen ovale and foramen
spinosum open on its roof, and the
alveolar canals on its anterior wall
THE ZYGOMATIC ARCH
 The zygomatic arch is a horizontal bar on
the side of the head,in front of the ear, a
little above the tragus.
 Formed by the temporal process of the
zygomatic bone (anterior 1/3) and the
zygomatic process of the temporal bone
zygoma (posterior 2/3).
 The zygomatico-temporal suture crosses the arch obliquely downwards
and backwards.
EXTERNAL ACOUSTIC MEATUS
 External acoustic meatus opens just
below the posterior part of the
posterior root of the zygoma.
 Its anterior and inferior margins and the
posterior margin are formed by the
tympanic plate, and the posteriosuperior margin is formed by the
squamous temporal bone.
SUPRAMEATAL TRIANGLE
 The suprameatal triangle is a small depression
posterio-superior to the meatus.
ASTERION
 The asterion is the point
where the parietomastoid, occipitomastoid and the
lambdoid sutures meet.
 In infants the asterion is the site of the posterio-lateral (mastoid)
fontanelle, which closes at the end of the first year.
PTERION
 It is situated about 3 cm. behind, and
a little above the level of the
zygomatic process of the frontal bone.
 It marks the junction between four
bones:
 Parietal bone
 Temporal bone
 Sphenoid bone
 Frontal bone
 The pterion is known as the weakest
part of the skull.
INFANTILE SKULL WITH
FONTANELLES
 At birth skull is not fully ossified
 Fontanels
Fibrous membranes
 connect the cranial bones.
 allow movement of the bones to
enable the skull to pass through the
birth canal
 The fontanels close as cranial bones
grow

squamosal
suture
lacrimal
bone
temporal
bone
external acoustic
meatus
mandibular condyle
In mandibular fossa
(TMJ joint)
Lateral Skull
zygomatic arch
sphenoid
bone
coronoid
process
sutural
bone
mastoid process
styloid process
ramus
Lateral Skull
The Adult Skull
angle body
mandible
STUDY OF SKULL
Skull can be studied from different views.The views so obtained are termed the normae
of the skull
– From Above- Norma Verticalis
– From Below- Norma Basalis
– From Front- Norma Frontalis
– From Back- Norma Occipitalis
– From Side- Norma Lateralis
– From Inside – Interior of skull
SUTURES OF OCCIPITAL REGION
SKULL POSTERIOR VIEW (NORMA OCCIPITALIS)
•
•
•
Circular outline.
Forms most of skull’s posterior and base
Major markings include
– Sagittal suture
– Lamboidal suture
– external occipital protuberance
– mastoid foramen
– foramen magnum,
– occipital condyles
– hypoglossal canal