The document describes the three cranial fossae (anterior, middle, posterior) and their boundaries. The anterior fossa is formed by the frontal bone, ethmoid, and lesser sphenoid wing and contains the frontal lobes. The middle fossa is formed by the sphenoid, temporal, and parietal bones and contains the temporal lobes. The posterior fossa is formed mainly by the occipital bone and contains the cerebellum and brainstem. It also discusses the orbital complex, nasal complex, infratemporal fossa, and muscles of mastication.

1. CRANIAL FOSSAE

2. The Cranial Fossae
Cranial fossa – curving depression of the cranial floor
• Anterior cranial fossa formed by:
- the frontal bone, the ethmoid, the lesser wing of the sphenoid; cradlesthe frontal lobes of the cerebral
hemispheres
• Middle cranial fossa is formed by:
- the sphenoid, temporal, parietal bones; cradlesthe temporal lobes of the cerebral hemispheres, the
diencephalon, and mesencephalon
• Posterior cranial fossa is formed primarily by:
- the occipital bone, with contributionsfrom the temporal and parietal bones
- suports the occipital lobesof the cerebralhemispheres, the cerebellum, and the pons and medulla
oblongata (brain stem)

3. Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
Cranial Base
• Internal aspect of the cranial base is
divided into three major regions or
fossae:
1. Anterior cranial fossa
2. Middle cranial fossa
3. Posterior cranialfossa
• These three fossae lie at different levels
and form the bowl-shaped floor of the
cranial cavity

4. The Cranial Fossae
Fig 6.11a

5. The Cranial Fossae

6. Ethmoid
Orbital portion of
the frontal bone
Lesser wing of
the sphenoid
Anterior Cranial Fossa
Frontal lobes of the brain occupies the anterior cranial
fossa
• Fossa is formed by the:
1. Orbital portion of the frontal bone
2. Ethmoid bone in the middle
3. Lesser wing of the sphenoid

7. Crista
galli
Frontal crest
Foramen cecum
Anterior Cranial Fossa
• Frontal crest- a median bony
extension from the frontal bone
• Foramen cecum is located at the
base of the crest and is a small
foramen for passage a vessels
during development
• Crista galli- ridge of bone
projecting superiorly from the
ethmoid bone and serves as the
attachment for the cerebral falx

8. 8
Anterior Cranial Fossa
• On either side of the crista galli
is a “sievelike” Cribriform
plate for passage of the
olfactoryaxons into the cranial
cavity
• Optic canal for passage of the
optic nerve (CN II) and the
ophthalmic artery can be
appreciated withinthe lesser
wing of the sphenoid
Cribriform plate
Optic canal

9. Greater wing
of sphenoid
Squamous
portion temporal
bone
Petrous portion
temporal bone
Middle Cranial Fossa
• Temporal lobes of the brain occupy
the middle cranial fossa
• Fossa is formed by the:
1. Greater wing of the sphenoid
2. Squamous portion of the temporal
bone
3. Petrous portion of the temporal bone

10. Middle Cranial Fossa
• Sella turcica- the saddle-like bony
formation located on the superior
aspect of the body of the sphenoid
• Sella turcica is surrounded by
anterior & posterior clinoid
processes
Sella
turcica
Anterior and
Posterior clinoids

11. Middle Cranial Fossa
• Sella turcica is composed of three parts:
1. Hypophyseal fossa (pituitary fossa)
2. Tuberculum sellae (saddle horn)
3. Dorsum Sellae (back of the saddle)
• Sella turcica- essentially houses and
guards the pituitary gland
Hypophyseal fossa
Tuberculum sellae
Dorsum sellae

12. Superior orbital fissure
Foramen rotundum
Foramen ovale
Middle Cranial Fossa
• Middle cranial fossa presents five
important foramina:
1. Superior orbital fissure for passage
of CN’s III, IV, V1 & VI &
ophthalmic veins
2. Foramen rotundum which transmits
the maxillarynerve (V2)
3. Foramen ovale- which transmitsthe
mandibularnerve (V3)

13. Foramen spinosum
Foramen
lacerum
Petrosal grooves
Middle Cranial Fossa
4. Foramen spinosum which transmitsthe middle
meningeal artery
5. Foramen lacerum- nothing is transmittedvertically
thru this foramenalthough the internal carotidartery
and some nerves pass across the foramenhorizontally
• Grooves for the greater & lesser petrosal nerves are
located along the anterior slope of the petrous portion
of the temporal bone

14. Arcuate eminence
Trigeminal impression
Middle Cranial Fossa
• Petrous portion of the temporal bone houses
the middle and inner ear cavities
• Arcuate eminence-marks the roof of the
anterior semicircularcanal of the inner ear
cavity
• Trigeminal impressionis locatedjust
anteromedial the eminence-which marksthe
locationof the sensory ganglion of the
trigeminal nerve

15. Posterior Cranial Fossa
• The largest & deepest of the three
fossae
• Cerebellum, pons and medulla
occupy the posterior fossa
• Formed mainly by the occipital bone
and the petrous & mastoid portions of
the temporal bone
Occipital
bone Temporal bone
Petrous portion

16. clivus
Occipital crest
Internal occipital
protuberance
Posterior Cranial Fossa
• Clivus marks the anteriorportion of the
occipitalbone
• Foramen magnum- large foramen that
marks the transitionfrom the medulla to
the spinal cord
• Posterior to the foramen magnum is the
internal occipital crest and internal
occipital protuberance

17. Transverse
Sinus groove
Groove for the
Sigmoid sinus
Jugular
foramen
• Broad grooves show the horizontal course of the
transverse and S-shaped sigmoid sinuses (both
dural venous sinuses)
• Sigmoid sinus empties into the large jugular
foramen which also transmits several cranial
nerves:
1. Glossopharyngeal (CN IX)
2. Vagus (CN X)
3. Accessory (CN XI)
Posterior Cranial Fossa

18. Hypoglossal
canal
Internal
acoustic
meatus
Posterior Cranial Fossa
• Internal acoustic meatus is locatedjust
anterosuperior to the jugular foramen
• Internal acoustic meatus transmitsthe
facial nerve (CN VII) and
vestibulochochlearnerve (CN VIII)
along with the labyrinthineartery
• Hypoglossal canal for the hypoglossal
nerve (CN XII) lies superiorto the
margin of the foramen magnum

19. 19
Cribrifrom plate-CN I
Optic Canal CN II
Superior Orbital Fissure
CN III, IV, V1 & VI
Hypoglossal Canal
CN XII
Jugular Foramen- CN IX, X and XI
Internal Acoustic Meatus-
CN VII & VIII
Foramen Rotundum- CN V2
Foramen Ovale-CN V3

20. Periorbital Sinuses
• The eyes lie within two bony orbits, located on either side of the root of
the nose.
• They border the nasal cavityanteriorly and the ethmoidalair cells and
the sphenoid sinus posteriorly.
• The lateralwalls border the middle cranial,temporal, and
pterygopalatinefossae.
• Superior to the orbit are the anterior cranial fossa and the frontal and
supraorbitalsinus.
• The maxillarysinus and the palatineair cells are locatedinferiorly.

21. Sectional Anatomy of the Skull

22. The Orbital Complex

23. Sectional Anatomy of the Skull

25. Orbital Complex: Eye socket
• medial wall: frontal process, lacrimalbone and part of ethmoid
• lateralwall: sphenoid, zygomatic
• floor: maxillary,zygomatic
• back: sphenoid + superior orbital
fissure
-top: frontal bone
• sphenoid and frontal bones
are separated by the infaorbital
fissure (infraorbital& zygomatic
nerves, infraorbitalartery
and inferior opthalmicvein)
-continues on as the infraorbital sulcus
-becomes the infraorbital canal
-terminateson the facialsurface as the
infraorbital foramen (infraorbitalnerve)

26. Orbit
pyramid-shaped paired cavities
• Base: supraorbital notch infraorbital foramen
• Apex: optic canal
• Walls
– Superior:
fossa for lacrimal gland
– Medial:
fossa for lacrimal sac
– Inferior:
infraorbitalfissure
– infraorbital groove
– infraorbital canal

27. Bony nasal cavity
• Roof: cribriform plate of ethmoid
• Floor: bony palate
• Lateral wall
– Three nasal conchae (superior,
middle and inferior)
– Nasal meatus underlying each concha (superior,middle and inferior)
– Sphenoethmoidal recess
above superior nasal concha
• Anterior ―piriform aperture
• Posterior ―posterior nasal aperture communicates with pharynx

28. Orbital Volume
• The volume of each adult orbit is slightlyless than 30 cc
• The orbitalentrance averages about 35 mm in height and
45 mm in width. The maximum width is about 1 cm
(behind the anterior orbital margin)
• In adults, the depth of the orbit varies from 40 to 45 mm
from the orbitalentrance to the orbital apex
• Both race and sex affect each of these measurements.

29. Bony Orbit
• Seven bones make up the bony orbit:
– Frontal
– Zygomatic
– Maxillary
– Ethmoidal
– Sphenoid
– Lacrimal
– Palatine

30. Inferior
orbital
fissure &
groove
Optic canal
Superior
orbital
fissure
Ethmoidal
foramina
Osteology of the Orbit
• Optic canal- transmits the optic nerve
and ophthalmic artery
• Superior orbital fissure- transmits
CN III, IV, V1 & VI
• Inferior orbital fissure & groove-
transmits the infraorbitalvessels &
nerve
• Anterior & posterior ethmoidal
foramina- transmits vessels & nerves
with same name

31. Orbital Roof
• The orbital roof formed from both the
orbital plate of the frontal bone and
the lesser wing of the sphenoid bone.
• Lacrimal gland
• Fovea trochlearis

32. Medial Orbital Wall
• Then medial wall of the orbit is
formed from four bones:
– Frontal process of the maxillary
– Lacrimal
– Orbitalplate of the ethmoidal
– Lesser wingof the sphenoid
• Lacrimalfossa
• Lamina papyracea

33. Orbital Floor
• The floor of the orbit is formed
from three bones:
– Maxillary
– Palatine
– Orbital plate of the zygomatic
• Infraorbital groove
• Inferior oblique muscle

34. Lateral Orbital Wall
• Formed from two bones:
– Zygomatic
– Greater wing of the sphenoid
• Thickest and strongest
• Lateral orbital tubercle
(Whitnall’s tubercle)

35. Orbital Foramina
• The optic foramen
• The supraorbitalforamen, or notch
• The anteriorethmoidalforamen
• The posterior ethmoidalforamen
• The zygomatic foramen
• Nasolacrimalduct
• Infraorbitalcanal
• Superior orbital fissure
• Inferiororbital fissure

36. Orbital fractures
• Floor fractures
– Maxillaryand zygomaticbones
• Orbital blowout
• Symptoms
– Double vision
– Sagging of the eye

37. • Bones and cartilage that enclose the
nasal cavity
The Nasal Complex

38. Nasal bones & cavities
• Nasal bones
– Paired bones – formsthe bridge
– Articulatewithfrontal bone
– nasion:junctionbetween frontal and nasal bones
deviatednasal septum: nasal septum dividesthe nasal cavity into right and left
halves
-three components: vomer, septalcartilage& perpendicularplate of the
ethmoid
-deviationresultsin a later deflectionof the septum
-severe deviationmay affect breathing
• Nasal cavity
– anterior, triangular opening: piriformaperture
-lateralwall: nasal conchae (superior, middle, inferior)
-superior and middle - ethmoid
-inferior nasal conchae – separate bone
-divided into separate cavities – nasal septum
-anterior portion is nasal septal cartilage
-superior portion formed by perpendicular plate
-inferior portion formed by the vomer

39. The Nasal Complex
• Paranasal sinuses are the interconnected hollow spaces inside the frontal,
ethmoid, sphenoid, and maxillary bones
• These spaces reduce the weight of the skull, produce mucus, and allow air to
resonate for voice production
• These paranasal sinuses are called the frontal sinus, maxillary sinus,
sphenoidal sinus, and the ethmoidal air cells

40. Paranasal Sinuses
• part of the nasal complex
• Paired cavitiesin ethmoid, sphenoid, frontal and
maxillary
• Lined with mucous membranesand open into
nasal cavity though openings called ostia
• Resonatingchambers for voice, lighten the skull
• Sinusitisis inflammationof the membrane
(allergy)
• infection can easily spread from one sinus to the
other through the nasal cavity
• can also spread to other tissues
– secondary sinusitis
• frontal sinuses:frontal bone, separated by a septum
– connects with nasal cavity – frontonasal duct
• sphenoid sinuses:body of the sphenoid bone
– also drain into nasal cavity
• ethmoid sinuses:or ethmoid air cells, located in the lateralmasses
– anterior, middle and posterior sinuses
• maxillary:body of the maxilla
– size varies with individual and age
– largest of the sinuses
– close proximity to alveolar processes – periodontal tissues may be in direct contact
with sinus’ mucus membranes

41. The Nasal Complex

42. The Nasal Complex

43. The Nasal Complex
Fig 6.16d

44. Cranial Fossae
• Depressions in cranial floor
• Anterior cranial fossa
– Frontal bone, ethmoid,lesser
wings of sphenoid
• Middle cranialfossa
– Sphenoid, temporal bones,
parietalbones
• Posterior cranial fossa
– Occipitalbone, temporal bones,
parietalbones

45. Cranial Fossae

50. Temporal fossa
Boundaries :
Above & behind - superior temporal line
Anterior wall - zygomatic bone
- zygomatic process of frontal bone
- greater wing of sphenoid bone
Medial wall - parietal bone, frontal bone,
squamous part of temporal bone,
greater wing of sphenoid bone
Inferior - infratemporal crest

52. Temporal fascia

53. Infratemporal fossa
Boundaries :
Anterior wall - posterior surface of maxilla
- maxillary tuberosity
Medial wall - lateral pterygoid plate
- pyramidal process of palatine bone
Lateral wall - inner surface of zygomatic arch
- ramus and coronoid process
Roof - infratemporal surface of greater
wing of sphenoid bone and
squamous part of temporal bone

54. Infratemporal fossa
Route :
cranial cavity orbit
infratemporal fossa
pterygopalatine fossa
Foramen ovale
Foramen spinosum Inferior orbital fissure
Pterygomaxillary fissure

55. Infratemporal fossa
Contents :
1. Medial & Lateral pterygoid muscle
2. Maxillary artery
3. Pterygoid venous plexus
4. Mandibular nerve
5. Chorda tympani
6. Otic ganglion

57. Muscles of mastication
Masseter muscle
Temporalis muscle
Medial pterygoid muscle
Lateral pterygoid muscle

58. Masseter muscle
Origin :
superficial portion - lower border of ant. 2/3 of
zygomatic arch
deep portion - lower border of post. 1/3 of
zygomatic arch
- medial surface of zygomatic
arch
Insertion : lateral surface of mandible extend from
basal part of coronoid process to angle
of mandible

60. Masseter muscle
Nerve supply : Nerve to masseter
Action : - elevation (bilateral)
- retrusion (bilateral)
- ipsilateral excursion (unilateral)

61. Temporalis muscle
Origin : floor of temporal fossa
Insertion : medial surface, apex, anterior and
posterior border of coronoid process
superficial tendon - anterior border of
coronoid process
deep tendon - internal oblique line

63. Temporalis muscle
Nerve supply : deep temporal branch of
mandibular nerve
Action : - resting tonus (bilateral)
- elevation (bilateral)
- retrusion (bilateral)
- ipsilateral excursion (unilateral)

64. Medial pterygoid muscle
Origin :
superficial head - maxillary tuberosity
- lateral surface of pyramidal
process of palatine bone
deep head - pterygoid fossa
- medial surface of lateral
pterygoid plate
Insertion : medial surface of mandibular angle

66. Medial pterygoid muscle
Nerve supply : nerve to medial pterygoid
Action : - elevation (bilateral)
- protrusion (bilateral)
- contralateral excursion (unilateral)

67. Lateral pterygoid muscle
Origin :
upper head- infratemporal surface and
infratemporal crest of greater wing
of sphenoid bone
lower head- lateral surface of lateral
pterygoid plate
Insertion : - anteromedial surface of
articular capsule
- anterior border of articular disc
- anterior surface of mandibular neck

69. Lateral pterygoid muscle
Nerve supply : nerve to lateral pterygoid
Action : - protrusion (bilateral)
- depression (bilateral)
- contralateral excursion (unilateral)

70. PTERYGOPALATINE FOSSA
• Located behind the zygomatic arch
• In back of the maxillary bone there is a cleft or a fissure (between
the maxillary bone and the pterygoid process of the sphenoid bone)
• Once across this fissure you are in the pterygopalatine fossa

73. Sutures
• Immovable joints (synarthrotic, fibrous joints)
• Form boundaries between skull bones
• Five sutures
– Coronal
– Sagittal
– Lambdoid
– Squamous
– Frontonasal

75. Oral Cavity Anatomy
• Buccal Cavity
– Lips-anterior entry
– Vestibule-between lips and teeth
– Teeth
– Palate
– Cheeks
– Tongue

76. Teeth
• Two dentitions
– Deciduous-6months to 2 to 4 years
• Centralincisors (2)
• Lateralincisors (2)
• Cuspids (canines) (2)
• Molars (4)
– Permanent-6years
• Molars (6 more)
– Wisdom teeth (17-25 years)

77. More Teeth
• Sides of teeth
– Labial-lip
– Lingual-tongue
– Buccal-cheek
• Imbedded in a socket of the alveolar
process of each jaw

78. Tooth function
• Speech
• Breakdown food
– Incisors-tear
– Cuspids-graspand shred
– Bicuspids and molars grind

79. Tooth Make-up
• Covered in enamel (calcium salts)
– Not replaced as worn down
• Dentin
– Majority of tooth
– Harder than bone
• Pulp
– Containsblood vessels, nerves, connective
tissue
• Areas
– Crown
– Root
– Neck

80. Palate
• Roof of the mouth
• Hard-anterior
• Soft-posterior
– Muscle and fat
– Uvula-lymphatictissue
– Rises during swallowing to keep food
out of the nose

81. Cheeks and Tongue
• Cheeks
– Skin
– Fat
– Muscles of mastication
• Tongue
– Muscle
– Mucous membrane
– Chemoreceptorsof taste
– Attachedto floor of mouth by the lingual
frenulum

82. Jaw Bones
• Malocclusion-misalignment of the teeth
– Over bite or under bite
• Acquired deformities-ear infections, disease processes, or trauma
• Micrognathia-small jaw
– Pierre Robin syndrome
• Macrognathia
– Paget’s disease-overgrowth of cranium, maxilla, and mandible
– Acromegaly-overgrowth of all bones

83. Mandibular fractures
• ORIF-mandibulomaxillaryfixation
• Types
– Symphysis
– Horizontalramus fractures
– Mandibular angle fractures
– Condyle and subcondylar

84. Frontal Fractures
• Anterior table fracture
• Posterior table fracture
• Signs
– Denting of forehead
– Leak of cerebrospinal fluid

85. Zygomatic Fractures
• Tri-malar fracture
– Zygomaticofrontal
– Zygomaticotemporal
– Zygomaticomaxillary
• Signs
– Dimpling of skin above cheek
– Sclaral or nasal hemorrhage

86. Midfacial Fractures
• Bones of the
– Maxilla
– Palatine
– Sphenoid
• 3 basic classes
– Le Fort I-teethseparatefrom base of the
skull
– Le Fort II-triangularin shape
– Le Fort III-highin the mid face
• Symptoms
– Malocclusion
– Movable alveolar process
– Flattenedfacial features
• Causes
– 53% automobileaccident
– 39% blunt trauma
– 8% gun shot

87. Le Fort Fractures