3. THE SKULL :- Consist of 28 bones
The skull :
cranium + the lower jaw
Upper facial skeleton :
the orbits + nasal cavity +
Facial skeleton :
The upper facial skeleton+
5. braincase : cranial base + cranial vault
The vault of the braincase:
2. Paired parietals
3. Greater wings of the sphenoid
4. Squamous part of the occipital
5. Squamous parts of the paired temporal bones.
7. 1. The coronal suture:
frontal bone + both parietal bones
2. The sagittal suture:
two parietal bones on midline of the skull
3. The lambdoid suture:
two parietal bones + occipital bone
4. The squamous suture:
parietal + temporal bones
The joints between the bones of the upper facial skeleton and
of the cranial vault, fibrous in nature
The joints in the central regions of the cranial base, consist of
9. PTERION OF THE SKULL
An irregular H-
-The greater wing
10. Pterion of the skull
•Overlies the middle meningeal artery
•Fracture to the pterion rupture the anterior branch hematoma
pressure on the cerebral cortex death in a few hours
13. FRONTAL BONE
Formes the forehead region
curves upwards and backwards from the
supraorbital margins to meet the parietal
bones at the coronal suture.
• supraorbital margin
• supraorbital notch (foramen)
• superciliary arch: a small elevation above the
supraorbital margin, forms the eyebrow ridge in
parietal, nasal, ethmoid, lacrimal, maxillary, and
19. Make up the greater part of the vault
• Articulate with each other in the median plane at the sagittal
• Anteriorly with the frontal bone
• posteriorly with the occipital bone
• Inferiorly with the wing of the sphenoid and the squamous part
of the temporal bone.
• situated close to the sagittal suture on the posterior part of
• transmit emissary veins
23. Forms posterior portion of the cranium and cranial base
Forms the posterior cranial fossa
Articulates with the temporal bones and parietal bones
Articulates with the first cervical vertebra (the atlas)
• Foramen magnum
• Basilar part (occiput)
• Squamous part
• External occipital crest
• External occipital protuberance
• Superior nucal line
• Inferior nucal line
24. Features cont.:
Occipital condyles: articulate with the atlas
vertebra to form the atlanto-occipital joints.
Pharyngeal tubercle: small elevation,
anterior to the foramen magnum, attachment
to the uppermost fibres of the superior
1) lateral to the condyle.
2) internal opening of this canal is situated
anterolateral wall of the foramen magnum.
3) transmits: hypoglossal nerve, meningeal
branch of the ascending pharyngeal artery.
30. THE ORBIT
Roof of the orbit is formed by:
• the inferior surface of the orbital part of the
• the inferior surface of the lesser wing of the
The lateral wall is formed by:
• the orbital surfaces of the zygomatic bone
• greater wing of the sphenoid
The lateral wall separates the orbital cavity
from the temporal fossa anteriorly and from
the middle cranial fossa posteriorly.
31. THE ORBIT
The floor of the orbit is formed by:
upper surface of the body of the maxilla
At the posteromedial corner of the orbital floor is
a small triangular area formed by the orbital
plate of the palatine bone
The medial orbital wall is formed by:
• the frontal process of the maxilla
• the lacrimal and the orbital plate of the
• the body of the sphenoid
32. SUPERIOR ORBITAL FISSURE
The lateral wall and roof are separated
posteriorly by the superior orbital fissure
• lying between the greater and lesser wings of the
1. the nerves to the muscles moving the eyeballs
2. the ophthalmic division of the trigeminal nerve
3. ophthalmic veins
34. INFERIOR ORBITAL FISSURE
The lateral wall and floor are similarly
separated by the inferior orbital fissure
• bordered by the maxilla and greater wing of
• posteromedial part the inferior fissure
communicates with the pterygopalatine fossa
• its anterolateral part communicates with the
35. Infraorbital groove :
• Starts from the medial part of the inferior orbital
fissure and continues forward
• Becomes roofed over to form orbital canal
• then opens on the front of the maxilla at the
Infraorbital foramen: transmit the
37. OPTIC CANAL
Above the superior orbital fissure
lying between the roots of the lesser wing of the
Transmits: The optic nerve and ophthalmic
1. anterior cranial fossa
2. the roof and lateral walls of the nasal cavity
3. the nasal septum
4. the medial walls of the orbits
consists of :
1. the perpendicular plate
2. the cribriform plate
3. the two labyrinth
41. PERPENDICULAR PLATE
thin lamina of bone which occupies the upper
part of the nasal septum.
possesses four margins:
1. The superior margin attached to the inferior
surface of the cribriform plate in the midline.
2. The anterosuperior margin articulates with
the frontal and nasal bones.
3. The posterior margin articulates in its upper
part with the crest of the sphenoid and in its
lowest part with the superior border of the
4. The anteroinferior surface is free in the dried
skull but in life provides the attachment for the
cartilage forming the anterior part of the nasal
42. CRIBRIFORM PLATE
lies horizontally, occupying the notch between
the orbital parts of the frontal.
1. the floor of the central part of the anterior
2. the roof of the middle part of the nasal cavity.
43. CRIBRIFORM PLATE
perpendicular plate: descends from its lower
crista galli: triangular plate projects upwards
from the midline of the cribriform plate, gives
attachment to the falx cerebri.
foramina for the olfactory nerves:
cribriform plate is pierced on either side of the
nasal slit: A narrow gap in the cribriform
plate, lies immediately adjacent to the crista
galli on each side.
consists two vertical laminae
-the medial plate
-orbital (lateral) plate
separated from each other by a number of thin-
walled ethmoidal air cells.
The orbital plate
• forms part of the medial wall of the orbit
• Articulation :
-above with the orbital part of the frontal
-below with the orbital surface of the maxilla and
orbital plate of the palatine
-in front with the lacrimal
-behind with the sphenoid
Projecting downwards and backwards from the
anterior part of the orbital plate is the thin
curved uncinate process, which helps form
the lateral wall of the middle meatus.
The medial plate
• forms the upper part of the lateral wall of the
• It is attached above to the inferior surface of the
• The lower edge of the plate projects into the
nasal cavity as a horizontal, rolled ridge called
the middle nasal concha.
NASAL CONCHAE AND
o Superior nasal concha:
• Between its upper and lower borders of the
• Above the superior concha is the
o Middle nasal concha: from lower edge
o Inferior nasal concha
uncinate process :forms the lateral wall of
53. THE SPHENOID BONE
Forms part of :
1. middle cranial fossa
3. nasal cavity
4. infratemporal fossa
Consists of :
1. central body
2. two greater wings
3. two lesser wings
4. two pterygoid processes.
56. BODY OF THE SPHENOID BONE
Cuboidal in shape
Hollowed out by the two sphenoidal air sinuses.
Articulates in front with the cribriform plate of the
ethmoid and behind with the basilar part of the
features of the superior surface:
1. optic groove
2. pituitary fossa
3. dorsum sellae (project as the posterior clinoid
The anterior border of the pituitary fossa frequently
bears two small lateral tubercles, the middle clinoid
58. BODY OF THE SPHENOID BONE
a median ridge on the anterior surface of the
body, below the articulation with the cribriform
this articulates with the posterior edge of the
perpendicular plate of the ethmoid.
Either side of the sphenoidal crest are the
openings of the sphenoidal sinuses.
provides the posterior part of the roof of the nasal
60. GREATER WINGS
The greater wings project laterally and upwards
from the sides of the body.
Each has a superior (cerebral), lateral, and
The superior surface forms the floor of the lateral
part of the middle cranial fossa
is pierced by foramina:
61. GREATER WINGS
The lateral surface:
• divided into upper (temporal) and lower (infratemporal) parts by
the infratemporal crest.
The infratemporal surface:
• foramina ovale
• foramina spinosum
• the spine of the sphenoid
The orbital surface:
• faces forwards and somewhat medially
• A horizontal ridge divides it into:
A large upper area, forming the posterior part of the lateral
A small lower area which provides the upper part of the posterior
boundary of the pterygopalatine fossa. Which is pierced medially
by the anterior opening of the foramen rotundum
62. GREATER WINGS
Margins of the greater wing:
• superior and lateral borders makes sutural connections at
its tip (i.e. in the region of the pterion) This border ends
posteriorly at the spine of the sphenoid.
• posterior border runs medially to the body of the
• medially it forms the anterior boundary of the foramen
63. GREATER WINGS
o Margins of the greater wing cont:
• Below the pterion a common border is shared between
the orbital and lateral surfaces. In its upper part this
articulates with the zygomatic bone.
• In its lower part the border turns medially to form the
lower margin of the orbital surface and the upper
boundary of the inferior orbital fissure.
• Medial to the pterion the common border is between the
orbital and superior surfaces.
• Laterally this border articulates with the orbital plate of
the frontal while medially it provides the inferior border
of the superior orbital fissure.
65. LESSER WINGS
project from the upper part of the body, anterior to the
The superior surface forms a small, posterior part of the
anterior cranial fossa.
The inferior surface provides :
1. superior boundary of the superior orbital fissure
2. a small area of the posterior part of the orbital roof.
The posterior surface: ends medially at a projection, the
anterior clinoid process.
The lesser wing is attached to the body of the sphenoid by
two roots between which lies the optic canal.
68. PTERYGOID PROCESSES
attached to the inferior surface of the sphenoid
bone in the region where the greater wing fuses
with the body.
consists of medial and lateral pterygoid
plates which are fused anteriorly.
The two plates diverge posteriorly to enclose the
Just below the body of the sphenoid the
pterygoid process is pierced by the pterygoid
69. PTERYGOID PROCESSES
upper part of anterior border:
provides the posterior boundaries of the
pterygopalatine fossa and pterygomaxillary
Inferiorly the two plates diverge leaving a fissure
into which fits the pyramidal process of the
Adjacent to this fissure the anterior border is
roughened for articulation with the
perpendicular plate of the palatine bone.
70. PTERYGOID PROCESSES
LATERAL PTERYGOID PLATE
o forms the medial wall of the infratemporal fossa
o origin for the inferior head of the lateral
o forms the lateral boundary of the pterygoid fossa
o gives attachment to the main part of the medial
72. PTERYGOID PROCESSES
MEDIAL PTERYGOID PLATE
The posterior border of the medial pterygoid
• Gives origin to the superior constrictor muscle
• Gives attachment to the pharyngobasilar fascia
(a component of the wall of the nasopharynx)
which is pierced by the auditory tube
73. PTERYGOID PROCESSES
• From lower end of the posterior border
• This gives attachment to the pterygomandibular
• The tendon of tensor veli palatini curves around
the hamulus in a groove on its anterior (inferior)
77. The periotic ossifies in the cartilage of the auditory
The squamous is an intramembranously ossifying element
which was originally part of the dermal armour shield.
The tympanic is also a dermal bone and is represented in
non-mammals by the angular, one of the numerous bones
of the lower jaw.
The styloid ossifies in the dorsal part of the cartilage of the
78. Contained within the periotic are the middle
ear (or tympanic) cavity and the cavity for
the internal ear.
Traversing the middle-ear cavity are the three
ossicles, malleus, incus, and stapes, which
convey vibrations from the ear drum to the
80. PETROUS PART
houses the tympanic and internal ear cavities.
it is composed of very hard bone.
It lies entirely within the cranial base,
wedged between the sphenoid and occipital bones with its
apex directed anteromedially.
It has anterior, posterior, and inferior surfaces.
81. PETROUS PART
The anterior surface forms part of the middle cranial fossa just
posterolateral to the apex (and to foramen lacerum in the
articulated skull) it is marked by the trigeminal impression
which lodges the trigeminal ganglion housed within the
Posterolateral to the trigeminal impression much of the anterior
surface is formed by a plate of bone called the tegmen tympani.
The tegmen tympani has two small openings from which grooves
may be traced leading forwards and medially.
The more posteromedial of the openings is the hiatus for the
greater petrosal nerve and the more anterolateral the
hiatus for the lesser petrosal nerve. The anterior edge of
the tegmen tympani projects downwards between the
squamous and tympanic parts of the temporal.
82. PETROUS PART
On the under surface of the cranial base this downturned edge can be seen
as a lip of bone in the medial part of the squamotympanic fissure, dividing
it into a posterior petrotympanic and an anterior petrosquamous part
The petrotympanic fissure leads into the tympanic cavity.
Its medial end is widened to form the canaliculus for the chorda
tympani through which that branch of the facial nerve escapes from the
tympanic cavity to the exterior of the skull.
The posterior surface of the petrous bone forms part of the posterior
cranial fossa, the superior border of the bone providing the boundary
between middle and posterior fossae. approximately in the centre of the
posterior surface is the opening of the internal acoustic meatus.
83. PETROUS PART
The inferior surface makes up part of the under surface of
the cranial base.
Very irregular and has a large, circular opening which
leads into the carotid canal and behind this the deep
jugular fossa which houses the superior bulb of the
internal jugular vein.
The ridge separating the carotid opening from the jugular
fossa is pierced by the canaliculus for the tympanic
branch of the glossopharyngeal nerve.
in front of the opening of the carotid canal, in the angle
between the petrous and squamous parts, is the opening of
the bony part of the auditory tube. This leads into the
84. PETROUS PART
With the soft tissues in place the tube is
continued medially in cartilage to open into the
The anterior border articulates laterally with the
squamous part of the temporal bone at the
petrosquamosal suture and medially with the
greater wing of the sphenoid at a cartilaginous
85. PETROUS PART
The posterior border articulates by a
cartilaginous joint with the occipital bone.
Immediately adjacent to the jugular fossa the
petrous and occipital bones are separated by a
wide gap, the jugular foramen.
The apex of the petrous bone forms the
posterolateral boundary of the foramen
lacerum and is here pierced by the inner
opening of the carotid canal.
86. MASTOID PART
the most posterior part of the temporal bone
bears on its external aspect a conical projection, the mastoid
process to which is attached the sternocleidomastoid
Medial to the process is a deep groove, the mastoid notch, for
the attachment of the posterior belly of the digastric muscle.
Further medially still is a shallow groove in which runs the
The endocranial surface is marked by a deep, curved groove for
the sigmoid sinus.
The mastoid part articulates by its superior border with the
parietal bone and by its posterior border with the occipital bone.
87. SQUAMOUS PART
is a large plate of bone which forms the lower part of the side wall
of the cranial vault and a small area of the lateral part of the
The temporal surface is smooth and forms much of the temporal
fossa from which the temporalis muscle takes origin.
Projecting forwards from the temporal surface is the zygomatic
process which articulates anteriorly with the zygomatic
bone to form the zygomatic arch.
The cerebral surface is marked by a number of depressions,
corresponding to the convolutions of the temporal lobes of the
cerebral hemispheres, and by grooves for the posterior branches
of the middle meningeal vessels.
88. SQUAMOUS PART
The inferior aspect of the squamous part bears the superior articular
surface of the temporomandibular joint formed by the articular tubercle
and the anterior part of the mandibular fossa.
The fossa is transversely widened and is bounded in front by the
articular tubercle and completed behind by the tympanic part of the
Located in the depth of the fossa, between the squamous and tympanic, is
the squamotympanic fissure. Only the squamous (i.e. anterior) part of the
fossa is articular, the tympanic plate being excluded from the
temporomandibular joint by the attachment of the capsule to the anterior
lip of the squamotympanic fissure
89. SQUAMOUS PART
Laterally, the posterior edge of the articular surface is
downturned to form a lip of bone called the postglenoid
Medially the squamotympanic fissure is divided, into
petrotympanic and petrosquamous portions by the lip of the
The articular tubercle is sometimes described as the anterior root
of the zygomatic process (the posterior root being the ridge of bone
which continues from the zygomatic process above the external
The posterosuperior border of the squamous part articulates with
the parietal bone and the anteroinferior border with the greater
wing of the sphenoid bone.
90. TYMPANIC PLATE
This is a curved plate of bone which is fused with the petrous,
mastoid, and squamous parts to complete the external acoustic
meatus. It partly ensheaths the base of the styloid process.
91. STYLOID PROCESS
The styloid process is a slender, curved bony
projection of variable length.
It is usually broken in the dried skull.
Its upper part is ensheathed by and fused with
the tympanic plate.
The process gives attachment to the styloid
muscles and the stylohyoid and stylomandibular
Between the styloid and mastoid processes is the
stylomastoid foramen through which the facial
nerve leaves the skull.
92. TYMPANIC CAVITY
Is a mediolaterally compressed space within the petrous bone.
In its lateral wall is the ear drum or tympanic membrane which
separates the cavity from the external acoustic meatus.
The medial wall is formed by the bony partition separating the
tympanic cavity from the internal ear.
This wall has two openings:
1. the fenestra vestibuli
2. fenestra cochleae.
93. TYMPANIC CAVITY
Vibrations are transmitted from the ear drum to the
internal ear by the three ossicles. The malleus is attached
to the drum by its manubrium (handle) and articulates
with the head of the incus.
The incus articulates with the head of the stapes and
the footplate of the stapes occupies the fenestra
94. TYMPANIC CAVITY
The fenestra cochleae is not closed by bone and
provides a release mechanism for the pressure
changes in the fluids of the internal ear produced
by the vibrations of the footplate at the fenestra
Pressure within the middle-ear cavity is
maintained at atmospheric level by means of the
auditory tube which connects the anterior part
of the cavity with the nasopharynx.
100. ANTERIOR CRANIAL FOSSA
houses frontal lobes of the cerebral hemispheres.
fossa is made up from:
-orbital parts of the frontal bone
-lesser wings of the sphenoid
The posterior boundary provided by the anterior
border of the optic groove.
Medially each lesser wing bears a prominent
projection termed the anterior clinoid process.
103. MIDDLE CRANIAL FOSSA
-the temporal lobes of the cerebral hemispheres
-the pituitary gland
-posterior borders of the lesser wings of the sphenoid
-anterior margin of the optic groove
-superior borders of the petrous parts of the temporal
central region: formed by the body of the sphenoid
lateral regions: formed by the corresponding greater
wing of the sphenoid, the anterior surface of the
petrous temporal and the inferior part of the squamous
105. Sitting on the floor of the lateral portion of the middle cranial fossa is
the temporal lobe
• pituitary (hypophysial) fossa: which houses the pituitary gland
(hypophysis cerebri), sella turcica
• optic groove: In front of the pituitary fossa
• optic canal: Follow groove laterally, situated between the roots of
the lesser wing transmitting the optic nerve and ophthalmic artery to
MIDDLE CRANIAL FOSSA
106. MIDDLE CRANIAL FOSSA
optic chiasma: In the cranial cavity the fibres of the optic
nerve undergo a partial decussation (crossing over), lies
just above the optic groove.
tuberculum sellae: a rounded swelling between the
pituitary fossa and the optic groove
dorsum sellae: Posterior to the fossa, the superolateral
angles form the posterior clinoid processes
107. MIDDLE CRANIAL FOSSA
superior orbital fissure:
• Between the greater and lesser wings
1. oculomotor nerve
2. trochlear nerve
3. abducent nerve
4. the ophthalmic division of the trigeminal nerve
5. the superior and inferior ophthalmic veins
108. MIDDLE CRANIAL FOSSA
The medial part of each greater wing is pierced
by three foramina.
• This runs directly forwards into the
• transmits the maxillary division of the trigeminal
109. MIDDLE CRANIAL FOSSA
• posterior to foramen rotundum
• opens downwards into the infratemporal fossa
• Through it passes:
1. the mandibular division of the trigeminal nerve
2. lesser petrosal nerve
(which may have its own separate foramen)
3. accessory meningeal artery
110. MIDDLE CRANIAL FOSSA
• postero-lateral to foramen ovale
1. the middle meningeal vessels
the main arterial and venous channels
to the meninges
2. the nervus spinosus
a meningeal branch of the mandibular
division of the trigeminal nerve
Occasionally other foramina may be present for
small emissary veins.
111. Foramen lacerum:
• a large opening with jagged edges
• Medial to the foramen ovale
• bounded by the petrous part of the temporal
bone and the body and greater wing of the
• Opening into its posterior wall is the carotid
• From its anterior wall the pterygoid canal
runs forwards to open into the pterygopalatine
fossa. It transmits the nerve of the pterygoid
112. At a level below these two openings the foramen
lacerum is closed by a plug of cartilage pierced by
only one or two small emissary veins.
114. POSTERIOR CRANIAL FOSSA
- largest and deepest of the three cranial fossae.
- It houses the cerebellum and brainstem (midbrain,
pons and medulla oblongata)
Its central zone, the clivus, is formed by the
body of the sphenoid, posterior to the dorsum
sellae and the basilar part of the occipital
posterior: petrous bones and the condylar and
squamous parts of the occipital bone.
116. Between the petrous temporal bone and the basilar and
condylar parts of the occipital bone is the petro-
The anteromedial part of the fissure is closed in life
by cartilage The posterolateral end of the fissure is
widened to form the jugular Foramen
The surface of the petrous temporal bone forming the
anterolateral wall of the foramen is hollowed out into a
deep depression, the jugular fossa.
Lateral to the jugular foramen the petrous and the
condylar part of occipital meet at a fibrous joint, the
117. internal occipital crest: bears a median ridge
behind the foramen magnum, which gives
attachment to a fold of dura mater called
the falx cerebelli, It ends above at the internal
A shallow groove, marking the course of the
transverse venous sinus, curves away from the
protuberance on each side.
Laterally the groove turns to run first
downwards and medially and then turns
forwards to reach the jugular foramen. This part
of the groove is occupied by the sigmoid sinus, a
continuation of the transverse sinus.
119. Foramen magnum transmits :
1. medulla oblongata (plus meninges)
2. spinal roots of the accessory nerves
3. vertebral arteries
4. number of other structures
125. THE FOUR MAXILLARY PROCESSES
which projects laterally from the body, at the junction of
its anterior and infratemporal surfaces, to form the anterior
part of the zygomatic arch
which projects upwards to articulate with the frontal bone
and enters into the medial wall of the orbit and lateral wall of
the nose as well as forming the bridge of the nose behind the
which projects medially to articulate with its fellow of
the opposite side - the two processes together forming the
anterior three-quarters of the bony palate
which projects downwards and contains the sockets
(alveoli) for the roots of the upper teeth. The alveolar process
ends posteriorly at the tuberosity.
128. THE MAXILLARY BODY
Roughly pyramidal in shape
Hollowed out by the maxillary sinus
The upper (orbital) surface of the body
occupies the floor of the orbit
The anterior surface forms the curved external
surface of the upper jaw
The posterior (infratemporal) surface
provides the anterior wall of the infratemporal
129. Above the incisor teeth the anterior surface has a
shallow depression termed the incisive fossa
laterally is the deeper canine fossa which is
separated from the incisive fossa by the canine
eminence produced by the root of the
Above the canine fossa is the infraorbital
130. The anterior surface ends medially at the
anterior nasal aperture.
At the inferior margin of this aperture the
maxillae of the two sides form a median
projection, the anterior nasal spine.
The surface ends below at a prominent rounded
eminence, the maxillary tuberosity, located
behind the last molar tooth.
132. More medially the lower part of the
infratemporal surface articulates with the
pyramidal process of the palatine bone
(the pyramidal process projects posterolaterally
from the junction of the perpendicular and
horizontal plates of the palatine to intervene
between the maxilla and pterygoid process)
while the upper part forms the anterior wall of
the pterygopalatine fossa.
134. posterior alveolar canals: openings through
which the posterior alveolar neurovascular
bundles reach the upper molar teeth
137. BONY PALATE
• provides the floor of the nasal cavity and
the roof of the mouth.
• Its anterior three-quarters: palatine processes
of the maxillae.
• its posterior one-quarter: the horizontal
plates of the palatine bones.
sutures of the palate
1. median suture: between the right and left
2. transverse suture: between the palatine
processes of the maxillae and the horizontal
plates of the palatines.
139. Incisive fossa
• in the midline.
• behind the central incisors.
• openings of the two incisive canals.
Greater and lesser palatine foramina
• Medial to the last molar tooth
• inferior openings of the greater palatine canal
which runs down from the pterygopalatine fossa.
• transmit nerves and vessels of the same name.
posterior nasal spine median projection on the
posterior border of the palate
141. 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
142. THE ZYGOMATIC BONE
The zygomatic arch
1. zygomatic process of the maxilla
2. zygomatic bone
3. zygomatic process of the squamous part of
The temporal fascia is attached to its sharp
upper border. The masseter muscle arises from
its inferior border and medial surface.
145. EXTERNAL SURFACE OF THE
vertical ridge: on The external surface below the
interproximal space between the central incisor teeth, This
indicates the line of fusion of the symphysis menti.
Mental protuberance: a raised area Inferior to vertical
ridge, gives the human chin its characteristic shape.
mental tubercle: more prominent area to lateral the
oblique line: a faint ridge Running backwards and upwards
from the mental tubercle. Below the last molar tooth the ridge
becomes more prominent before becoming continuous with the
anterior border of the ramus.
mental foramen: above the oblique line, in the region of the
premolar teeth, transmits the mental branches of the inferior
alveolar nerve and blood vessels
148. INTERNAL SURFACE OF THE BODY
begins below the last molar tooth as a prominent
crest and runs forwards and downwards to end
by becoming indistinct in the region below the
canine and incisor teeth.
a concave area below the mylohyoid line contains
the submandibular gland.
sublingual fossa: a concave area Immediately
above the mylohyoid line, in the region below the
premolar teeth, contains the sublingual
149. INTERNAL SURFACE OF THE BODY
superior and inferior mental spines:
The inferior part of the internal surface below
the incisor teeth bears two small elevations, for
attachment of the genial muscles.
alveolar process: upper part of the body of the
mandible, contains sockets for the roots of teeth
digastric fossa: small, roughened area on the
inferior border of the body for attachment of the
anterior belly of the digastric muscle.
152. RAMUS OF THE MANDIBLE
a plate of bone.
mandibular foramen : Approximately at its centre
transmits the inferior alveolar nerve and blood
vessels. And leads into the mandibular canal.
Lingula: a thin plate of bone, on the anterior border
of the foramen .
mylohyoid groove: begins at the lower border of the
mandibular foramen, just behind the lingula, it runs
downwards and forwards onto the body of the
The area posteroinferior to the mylohyoid groove is
roughened for insertion of the medial pterygoid
angle of the mandible: The region where the
inferior and posterior borders of the ramus meet.
154. SUPERIOR BORDER OF THE RAMUS
coronoid and condylar processes are separated
from each other by the mandibular notch
The coronoid process: triangular plate, projects
upwards and forwards
• temporal crest: is a faint ridge On the medial aspect
of the coronoid process, which becomes more
prominent as it is traced downwards towards the
margin of the alveolar bone medial to the last molar
• retromolar fossa: Between the temporal crest and
the anterior border of the ramus
The superior and anterior margins of the
coronoid process and the retromolar fossa
provide the area of insertion of the temporalis
155. SUPERIOR BORDER OF THE RAMUS
condylar process: head of the mandible.
• superior and posterior surfaces of the head are
covered with fibrocartilage and articulate with the
articular surface of the squamous part of the temporal
at the synovial temporomandibular joint.
• condylar Head: wide from side to side but narrow
from front to back.
• condylar neck : The constricted part of the condylar
process below the head,
• pterygoid fovea: a shallow depression in the
anterior aspect of the neck , into which part of the
lateral pterygoid muscle is inserted.
Hinweis der Redaktion
The plate of bone forming the floor of the braincase is termed the cranial base.. The
roof and side walls of the braincase are called the cranial vault
After birth neither the sutures nor the synchondroses allow movement but both are
important growth sites. At the time of birth the sutures of the vault are sufficiently
flexible to allow some overriding of adjacent bones (called moulding) which allows the
head, usually the first part to be born
The junction(intersection) between the coronal and sagittal sutures is called the bregma
The junction(intersection) between the sagittal suture and lambdoid sutures is called the lambda
The vertex is the most superior point of the skull near the midpoint of the sagittal suture
supraorbital notch (foramen)
At the junction of the lateral two-thirds and
medial one-third of the supraorbital margin is the
In immature skulls a suture, termed frontal or metopic, is present in the median plane
of the frontal bone dividing it into right and left halves and indicating its development
from two ossification centres. In the majority of individuals the frontal suture fuses
during early childhood 6-8 yrs old ,,,,but in a few it persists, in whole or in part, into adult life.
The right and left parietal bones make up the greater part of the vault. They articulate
with each other in the median plane at the sagittal suture. Anteriorly they articulate
with the frontal bone at the coronal suture and posteriorly with the squamous part of
the occipital bone at the lambdoid suture. Laterally each parietal bone extends
downwards to form part of the lateral wall of the vault. Inferior to the parietal bone
the lateral wall of the vault is completed by the greater wing of the sphenoid and the
squamous part of the temporal bone.
The bones of the vault are pierced by a number of small foramina which transmit
emissary veins, connecting the intracranial dural venous sinuses with extracranial
veins, and also, in some cases, small arterial branches to the meninges. The most
constant are the parietal foramen (situated close to the sagittal suture on the
posterior part of the parietal)
The part of the occipital bone in front of the foramen magnum is called the basilar part, often referred to as the base of the occiput. The occipital bone that&apos;s behind the foramen magnum, the squamous part.
The occipital region of the vault has a number of ridges marking the attachment of the
extensor (nuchal) musculature of the neck. In the midline is the external occipital
crest which begins at the posterior margin of the foramen magnum and ascends on the
squamous part of the occipital bone to end at a prominence termed the external
Features and structures
Occipital condyles:The occipital condyles are the joint surfaces which articulate with the atlas vertebra to form the atlanto-occipital joints
On either side of the foramen are the downwardly
projecting occipital condyles. These provide the surfaces by which the skull articulates
with the first cervical vertebra (the atlas) at the synovial atlanto-occipital joints. As
already noted the hypoglossal canal opens lateral to the condyle.
A short distance
anterior to the foramen magnum is a small median elevation, the pharyngeal
tubercle. It gives attachment to the uppermost fibres of the superior constrictor
Just posterior to the junction of its basilar and condylar parts (i.e. some distance
medial to the jugular foramen), the occipital bone is pierced by the hypoglossal canal.
The internal opening of this canal is situated in the anterolateral wall of the foramen
magnum. The canal opens on the inferior surface of the skull lateral to the occipital
condyle and transmits the hypoglossal nerve and a meningeal branch of the ascending
between its upper and lower borders the medial plate
The middle concha forms the roof of the middle meatus, the lateral wall of which is completed by the uncinate process and the nasal surface of the maxilla.
The sphenoid ossifies from numerous centres, mostly within the cartilage of the cranial
base. The principal exceptions are the lateral parts of the greater wings and the
pterygoid processes which ossify intramembranously
The inferior surface of the body projects in the median plane to form the rostrum. This
articulates with the groove in the upper
border of the vomer, between its two alae. Posteriorly the lateral part of the inferior
surface is covered by the vaginal process of the medial pterygoid plate.
The anterior margin
articulates with the orbital plate of the frontal.
pterygoid hamulus:a laterally curving process,
At its upper end the posterior border splits to enclose the small scaphoid fossa, the area of origin of part of the tensor veli palatini muscle.
Immediately above and medial to the scaphoid fossa is the posterior opening of the pterygoid canal.
On the lateral aspect of the external surface of the vault are the superior and inferior
temporal lines. These begin anteriorly as a single line which is continuous with the
prominent ridge on the part of the frontal that articulates with the zygomatic bone.
The two lines diverge as they pass posteriorly and then arch together, about 1 cm
apart, across the frontal and parietal bones. Posteriorly the superior temporal line
fades away but the inferior line becomes more prominent and curves downwards and
forwards across the squamous part of the temporal to become continuous with the
posterior root of the zygomatic arch. The area on the lateral wall of the vault bounded
by the superior temporal line is called the temporal fossa. The roof of the fossa is
formed by the temporal fascia which is attached superiorly to the superior temporal
line and inferiorly to the upper border of the zygomatic arch. The temporal muscle
takes origin from the inferior temporal line and the area of bone which it encloses on
the lateral wall of the cranial vault.
the jugular foramen is the prominent mastoid process of the temporal bone which
gives insertion to the sternocleidomastoid muscle. Immediately medial to the mastoid
process is a deep cleft, the mastoid notch, from which the posterior belly of the
digastric muscle takes origin. Between the mastoid and styloid process is the
stylomastoid foramen through which the facial nerve leaves the skull.
The temporal bone of the lateral aspect of the skull
a squamous part which articulates with the greater wing of sphenoid at the sphenosquamous suture
a zygomatic process which articulates with the zygomatic bone to form the zygomatic arch
a tympanic part which has the external acoustic meatus
a petromastoid part which is usually separated into the petrous and mastoid part
A large bony prominence projects from the inferior border of the mastoid part of the temporal bone called the mastoid process
Medial to the mastoid process is the styloid process which projects from the lower border of the temporal bone
The point where the superior temporal line cuts the coronal suture is called the stephanion
While the located at junction of three sutures: parietomastoid, occipitomastoid, and lambdoid is called the asterion
The orbital parts of the frontal bone are separated from each other by a narrow gap
occupied by the cribriform plate of the ethmoid. Behind the cribriform plate the
central part of the fossa is completed by the part of the body of the sphenoid located
between the lesser wings. Between the cribriform plate and the body of the sphenoid is
the sphenoethmoidal joint which is initially cartilaginous but becomes
fibrous soon after birth. The posterior boundary of the fossa in this region is provided
by the anterior border of the optic groove.
Opening on the line of the suture between the cribriform plate and the orbital part of
the frontal are the anterior and posterior ethmoidal canals. The former transmits the
anterior ethmoidal nerve and vessels from the orbit to the anterior cranial fossa; the
latter transmits the posterior ethmoidal vessels only. The anterior ethmoidal nerve and
vessels pass from the anterior cranial fossa into the nasal cavity through the nasal slit.
carotid canal: a large sinuous channel traversing the petrous bone and transmitting the internal carotid artery.
. In the
immature skull these elements are separated by the sphenoccipital synchondrosis.
This cartilaginous joint begins to fuse in the early teens and has
completely disappeared in the adult skull. The lateral parts of the fossa are formed by
Opening on to the posterior surface of the petrous bone, some distance above the
jugular foramen, is the internal acoustic meatus. It transmits the vestibulocochlear
nerve and the motor and sensory roots of the facial nerve.
openings of the two incisive canals which communicate above with the corresponding halves of the nasal cavity
Leading forwards from the greater palatine foramen is a groove of variable distinctness which lodges the greater palatine neurovascular bundle
In many skulls the bone either side of the median suture
is heaped up to form a ridge. When pronounced this ridge is called the palatine torus.
the sphenoidal air
sinus into the sphenoethmoidal recess;
The palatine bone consists of horizontal and perpendicular plates
At birth the right and left halves of the mandible are united in the midline of the chin
region by a fibrocartilaginous joint, the symphysis menti. During the first year of
postnatal life this joint is obliterated by fusion of the two halves of the mandible
Note that the canal leading inwards from the foramen runs forwards and
downwards and that the foramen itself has sharp anterior and inferior borders but smooth posterior and superior borders, indicating that the mental branches run backwards and somewhat upwards.
from the ramus into the submandibular fossa is the shallow mylohyoid groove which
fades out anteriorly. This marks the course of the mylohyoid branches of the inferior
alveolar nerve and vessels. The area above the mylohyoid line has a smooth somewhat
convex form and in life is covered over most of its extent by the fused mucous
membrane and periosteum (mucoperiosteum) of the lower gum