Anatomy Osteology

2. CONTENTS
 INTRODUCTION
 SKULL INDIVIDUAL BONES
FRONTAL
PAREITAL
OCCIPITAL
ORBITAL
TEMPORAL
SPHENOID
ETHMOID
MAXILLA
ZYGOMATIC
PALATINE
MANDIBLE

3.  THE SKULL :- Consist of 28 bones
The skull :
cranium + the lower jaw
Upper facial skeleton :
the orbits + nasal cavity +
upper jaw
Facial skeleton :
The upper facial skeleton+
lower jaw

5.  braincase : cranial base + cranial vault
 The vault of the braincase:
1. Frontal
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
Sutures:
The joints between the bones of the upper facial skeleton and
of the cranial vault, fibrous in nature
Synchondroses:
The joints in the central regions of the cranial base, consist of
hyaline cartilage

9. PTERION OF THE SKULL
An irregular H-
shaped arrangement
of sutures
-Frontal bone
-Parietal bone
-The greater wing
-Squamous temporal

10. Pterion of the skull
10
•Overlies the middle meningeal artery
•Fracture to the pterion  rupture the anterior branch  hematoma
 pressure on the cerebral cortex  death in a few hours

11.  CRANIAL VAULT
AND BASE BONES
1. Frontal
2. Occipital
3. Sphenoid
4. Ethmoid
5. Parietal (2)
6. Temporal (2)
7. Malleus (2)
8. Incus (2) ear ossicles
9. Stapes (2)
 FACIAL BONES
1. Nasal (2)
2. Maxillae (2)
3. Zygomatic (2)
4. Palatine (2)
5. Lacrimal (2)
6. Inferior nasal conchae
(2)
7. Mandible
8. vomer

12. FRONTAL BONE

13. FRONTAL BONE
 Formes the forehead region
 curves upwards and backwards from the
supraorbital margins to meet the parietal
bones at the coronal suture.
 Features :
• supraorbital margin
• supraorbital notch (foramen)
• superciliary arch: a small elevation above the
supraorbital margin, forms the eyebrow ridge in
 Articulation :
parietal, nasal, ethmoid, lacrimal, maxillary, and
zygomatic bones.

14. FRONTAL BONE

15. FRONTAL BONE Glabella: Between the arches
a smooth, slightly depressed
area.

16. NASION: a depressed
area (bridge of the nose) ,
intersection of the frontal
and nasal bones

18. PARIETAL BONES

19.  Make up the greater part of the vault
 Articulation:
• Articulate with each other in the median plane at the sagittal
suture.
• 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.
 Parietal foramen:
• situated close to the sagittal suture on the posterior part of
the parietal
• transmit emissary veins

20. PARIETAL BONES

22. OCCIPITAL BONE

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)
beneath it
 Parts:
• Foramen magnum
• Basilar part (occiput)
• Squamous part
 Features:
• 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
constrictor muscle.
Hypoglossal foramen:
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.

28. ORBITAL BONE

30. THE ORBIT
 Roof of the orbit is formed by:
• the inferior surface of the orbital part of the
frontal bone.
• the inferior surface of the lesser wing of the
sphenoid.
 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
ethmoidal labyrinth
• 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
sphenoid
• transmits:
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
sphenoid
• posteromedial part the inferior fissure
communicates with the pterygopalatine fossa
• its anterolateral part communicates with the
infratemporal fossa.

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.
 Infraorbital foramen: transmit the
infraorbital nerve

37. OPTIC CANAL
 Above the superior orbital fissure
 lying between the roots of the lesser wing of the
sphenoid.
 Transmits: The optic nerve and ophthalmic
artery

39. ETHMOID

40. ETHMOID
 contributes to
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
vomer.
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.
 Forms:
1. the floor of the central part of the anterior
cranial fossa
2. the roof of the middle part of the nasal cavity.

43. CRIBRIFORM PLATE
Features:
 perpendicular plate: descends from its lower
surface.
 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
crista galli
 nasal slit: A narrow gap in the cribriform
plate, lies immediately adjacent to the crista
galli on each side.

44. LABYRINTHS
 consists two vertical laminae
-the medial plate
-orbital (lateral) plate
 separated from each other by a number of thin-
walled ethmoidal air cells.
 relatively fragile.

45. LABYRINTHS
 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

46. LABYRINTHS
 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.

47. LABYRINTHS
 The medial plate
• forms the upper part of the lateral wall of the
nasal cavity.
• It is attached above to the inferior surface of the
cribriform plate.
• The lower edge of the plate projects into the
nasal cavity as a horizontal, rolled ridge called
the middle nasal concha.

49. LABYRINTHS
NASAL CONCHAE AND
MEATUS
o Superior nasal concha:
• Between its upper and lower borders of the
medial plate
• Above the superior concha is the
sphenoethmoidal recess
o Middle nasal concha: from lower edge
o Inferior nasal concha
 uncinate process :forms the lateral wall of
middle meatus

52. THE SPHENOID
BONE

53. THE SPHENOID BONE
 Forms part of :
1. middle cranial fossa
2. Orbit
3. nasal cavity
4. infratemporal fossa
 Consists of :
1. central body
2. two greater wings
3. two lesser wings
4. two pterygoid processes.

54. THE SPHENOID BONE

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
occipital bone
 features of the superior surface:
1. optic groove
2. pituitary fossa
3. dorsum sellae (project as the posterior clinoid
processes)
The anterior border of the pituitary fossa frequently
bears two small lateral tubercles, the middle clinoid
processes.

58. BODY OF THE SPHENOID BONE
Sphenoidal crest:
 a median ridge on the anterior surface of the
body, below the articulation with the cribriform
plate
 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
cavity.

60. GREATER WINGS
 The greater wings project laterally and upwards
from the sides of the body.
 Each has a superior (cerebral), lateral, and
orbital surface.
 The superior surface forms the floor of the lateral
part of the middle cranial fossa
 is pierced by foramina:
1. rotundum
2. ovale
3. spinosum

61. GREATER WINGS
 The lateral surface:
• convex
• 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
orbital wall
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
sphenoid.
• medially it forms the anterior boundary of the foramen
lacerum.

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
greater wings.
 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.

66. 66

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
pterygoid fossa.
 Just below the body of the sphenoid the
pterygoid process is pierced by the pterygoid
canal.

69. PTERYGOID PROCESSES
 upper part of anterior border:
provides the posterior boundaries of the
pterygopalatine fossa and pterygomaxillary
fissure.
 Inferiorly the two plates diverge leaving a fissure
into which fits the pyramidal process of the
palatine bone.
 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
lateral surface:
o forms the medial wall of the infratemporal fossa
o origin for the inferior head of the lateral
pterygoid muscle
medial surface
o forms the lateral boundary of the pterygoid fossa
o gives attachment to the main part of the medial
pterygoid muscle.

71. PTERYGOID PROCESSES
MEDIAL PTERYGOID PLATE
 medial surface forms the lateral boundary of the
nasal aperture
 lateral surface forms the medial wall of the
pterygoid fossa.

72. PTERYGOID PROCESSES
MEDIAL PTERYGOID PLATE
The posterior border of the medial pterygoid
plate
 lower two-thirds:
• Sharp
• Gives origin to the superior constrictor muscle
 upper one-third:
• Blunter
• Gives attachment to the pharyngobasilar fascia
(a component of the wall of the nasopharynx)
which is pierced by the auditory tube

73. PTERYGOID PROCESSES
 Pterygoid hamulus:
• From lower end of the posterior border
• This gives attachment to the pterygomandibular
raphe.
• The tendon of tensor veli palatini curves around
the hamulus in a groove on its anterior (inferior)
border.

74. THE SPHENOID BONE

75. TEMPORAL BONE

76. TEMPORAL
 bone consisting of four fused elements:
1. periotic
2. squamous
3. tympanic
4. styloid

77.  The periotic ossifies in the cartilage of the auditory
capsule.
 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
hyoid arch.

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
internal ear.

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
trigeminal cave.
 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
nasopharynx.
 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
joint.

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
muscle.
 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
occipital artery.
 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
cranial base.
 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
temporal bone.
 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
tubercle.
 Medially the squamotympanic fissure is divided, into
petrotympanic and petrosquamous portions by the lip of the
tegmen tympani.
 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
acoustic meatus).
 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
ligaments.
 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
vestibuli.

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
vestibuli.
 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.

95. TEMPORAL BONE

97. INTERNAL SURFACE
OF THE CRANIAL
BASE
(CRANIAL CAVITY)

98. subdivided into three regions
1. Anterior cranial fossae
2. Middle cranial fossae
3. Posterior cranial fossae

99. 99

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.

102. 102

103. MIDDLE CRANIAL FOSSA
-the temporal lobes of the cerebral hemispheres
-the pituitary gland
Boundries
 Anterior :
-posterior borders of the lesser wings of the sphenoid
-anterior margin of the optic groove
 posterior :
-superior borders of the petrous parts of the temporal
bones
 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
temporal bone.

104. 104

105. Sitting on the floor of the lateral portion of the middle cranial fossa is
the temporal lobe
Features:
• 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
the orbit.
105
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
• transmits:
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.
 foramen rotundum:
• This runs directly forwards into the
pterygopalatine fossa
• transmits the maxillary division of the trigeminal
nerve

109. MIDDLE CRANIAL FOSSA
 Foramen ovale
• 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
 Foramen spinosum
• postero-lateral to foramen ovale
• Transmits:
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
sphenoid.
• Opening into its posterior wall is the carotid
canal
• 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.

113. 113

114. POSTERIOR CRANIAL FOSSA
- largest and deepest of the three cranial fossae.
- It houses the cerebellum and brainstem (midbrain,
pons and medulla oblongata)
Boundries
 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
bone
 posterior: petrous bones and the condylar and
squamous parts of the occipital bone.

115. 115

116.  Between the petrous temporal bone and the basilar and
condylar parts of the occipital bone is the petro-
occipital fissure.
 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
petro-occipital suture

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
occipital protuberance.
 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

120.  Jugular foramen transmits:
1. glossopharyngeal nerve
2. vagus nerve
3. accessory nerve
4. sigmoid venous sinuses
5. inferior petrosal venous sinuses

121. 121
internal acoustic
meatus
1. Vestibulocochlear nerve
2. facial nerve

123. THE UPPER JAW
AND BONY PALATE

124. MAXLLIA
-made up of the two maxillae
-Each consists of a body and four
processes

125. THE FOUR MAXILLARY PROCESSES
 zygomatic process
which projects laterally from the body, at the junction of
its anterior and infratemporal surfaces, to form the anterior
part of the zygomatic arch
 frontal process
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
nasal bone
 palatine process
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
 alveolar process
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
fossa

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
canine
 Above the canine fossa is the infraorbital
foramen.

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

136. BONY PALATE

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
sides
2. transverse suture: between the palatine
processes of the maxillae and the horizontal
plates of the palatines.

138. BONY PALATE

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
 The temporal fascia is attached to its sharp
upper border. The masseter muscle arises from
its inferior border and medial surface.

143. 143
Zygomatic Bones (Anterior View) (Pink Colored
Bones)

144. MANDIBLE
The mandible consists of
1.a body
2.two vertical rami

145. EXTERNAL SURFACE OF THE
BODY
 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
protuberance.
 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
 mylohyoid line:
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.
 submandibular fossa:
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
mandible.
 The area posteroinferior to the mylohyoid groove is
roughened for insertion of the medial pterygoid
muscle
 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
tooth.
• 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.