osteology of head and neck is explained in complete detail. It has two part. plz read both parts to get an complete overview about the osteology of head and neck region.

1. OSTEOLOGY
OF
HEAD & NECK (I)
Presented By:
Dr. Anil Kumar Godara

2. CONTENTS
 INTRODUCTION
 EXTERIOR OF THE SKULL - I) NORMA VERTICALIS
2) NORMA FRONTALIS
3) NORMA LATERALIS
4) NORMA OCCIPITALIS
5) NORMA BASALIS
 INTERIOR OF THE SKULL – 1) INTERIOR CRANIAL FOSSA
2) MIDDLE CRANIAL FOSSA
3) POSTERIOR CRANIAL FOSSA
 MANDIBLE
 MAXILLA
 HYOID BONE
 CERVICAL VERTEBRAE
 REFERENCES

3. INTRODUCTION:-
The bones of head and neck includes somatic bones ,SKULL - skull
with mandible, seven cervical vertebrae and hyoid bone.
SKULL= CRANIUM+ MANDIBLE
The cranium has further two parts
1) Neurocranium 2) Viscerocranium / splancocranium
• Neurocranium:-
• a) Roof of the cranial vault, dome like Calvaria (skull cap) which is
formed by- Frontal, parietal, squamous, temporal and part of occipital bone.
• b)Base of the skull ( Basicranium)

4. Viscerocranium/ Splancocranium:-
- Nasal cavity
- Orbital
- Bony plates
- Maxilla
- Mandible

5. THE SKULL:
 The Skeleton of the head is called the
skull.
 Skull can be divided into 2 main parts.
1) The calvaria or brain box
2) The facial skeleton
 Skull joints are immovable and fibrous
in type (except Temoromandibular
joint)

6.  SKULL consist of 28 bones which are as follows:-
 (A) The calvaria or brain case is composed of 8 bones in
adults.
(B) The facial skeleton is composed of 14 bones in adults (C) Ear Ossicles
PAIRED UNPAIRED
1. Parietal 1.Frontal
2.Temporal 2.Occipital
3.Sphenoid
4.Ethmoid
PAIRED UNPAIRED
1. Maxilla 1.Mandible
2.Zygomatic 2.Vomer
3.Nasal
4.Lacrimal
5.Palatine
6.Inferior nasal concha
 Bones of the Skull:
PAIRED
1. Malleus
2. Incus
3. Stapes

8. FOETAL SKULL
 In foetus, skull is large in proportion to other parts of skeleton.
 DIMENSIONS:
 Is small compared to calvaria. due to rudimentary mandible and maxilla, non
erupting teeth, small size of maxillary sinus and nasal cavity.
 The facial skeleton is 1/8th of calvaria where as in adults it is ½ of calvaria.
 The base of the skull is also short and narrow.

9.  STRUCTURES OF BONE
 The bones of cranial vault are smooth and unilamellar . There is no diploe.
 The tables and diploe occurs by 4th yr. of age.
 BONY PROMINENCIES
 Frontal and parietal tuber are prominent.
 Glabella , superciliary arches and mastoid process are not developed.

10.  OSSIFICATION OF BONE
i. Two haves of frontal bone is
separated by metopic suture.
ii. Mandible is also present in two
halves.
iii. The occipital bone is in four halves
( 1 squamous ,2 condylar,1 basilar)
iv. The four bony elements of the
temporal bone is separate except for
the commencing union of tympanic
part with squamous and petrous part.
v. Unossified membranous gap of six
fontanelle is at the angle of parietal
bone are present.

11.  PARANASAL SINUSES: are rudimentary or absent.
 TEMPORAL BONE:
 The internal ear ,tympanic cavity, tympanic antrum and ear ossicles are of adult
size.
 Mastoid process is absent and it appears during the later part of second year. This
occurs due to muscle activity of sternocleidomastoid muscle when the child moves
its head.
 The external acoustic meatus is short and straight . Its bony part is unossified and
represented by fibrocartilagenous plate.
 Tympanic membrane faces more downward than laterally due to the absence of
mastoid process.

12.  Stylomastoid foramen is exposed on lateral surface of the skull because mastoid portion is
flat, eventually exposing facial nerve behind pinna. Hence precaution has to be taken to
protect the facial nerve when an incision is to be made to open abscess behind pinna.
 Styloid process lies immediately behind the tympanic ring and is not fused with remaining
of the of temporal bone.
 Mandibular fossa is flat and is placed more laterally and articular tubercle is not
developed.
 ORBITS:
 Orbits are large . The germs of the developing tooth lies close to the orbital floor.
 POST NATAL GROWTH OF SKULL:
 The growth of calvaria and facial bone proceeds at different rates and over different
periods.
 Growth of calvaria is related to growth of brain where as that of facial skeleton is due to
development of dentition, muscles of mastication and of tongue.
 The rate of growth of the base and vault is also different

13. (A) GROWTH OF VAULT:
i. Rate - rapid during first years and slows upto seventh year when it is almost adult
size.
ii. Growth in breadth – the growth occurs at sagittal suture, sutures bordering
greater wing, mastoid suture and parieto-occipital suture at the base.
iii. Growth in height – this growth occurs at frontozygomatic suture, pterion ,
squamous suture and asterion.
iv. Growth in anterior posterior diameter – this growth occurs at coronal and
lambdoid suture.
(B) GROWTH AT BASE:
i. The base grows in anterioposterior diameter at three cartilagenous plates
situated between occipital & sphenoidal, between pre and post sphenoidal,
between sphenoidal and ethmoidal.

14. (C) GROWTH OF THE FACE:
i. The growth of orbits and ethmoid is completed by seventh year.
ii. The face growth occurs mostly during first year although it is continues till
puberty and even later.
 CLOSURE OF FONTANELLES:
FONTANELLE AGE
1) ANTERIOR FONTANELLE 18-24 MONTHS
2) MASTOID FONTANELLE 6-18 MONTHS
3) POSTERIOR FONTANELLE 2 -3 MONTHS
4) SPHENOIDAL FONTANELLE 5-6 MONTHS

15.  THICKENING OF BONES:
i. Two tables and diploe appears by fourth year.
ii. Differentiation reaches maximum by about 35 years when diploe veins
produce characteristic markings in radiographs.
iii. Mastoid process appears during second year and mastoid cells during sixth
year.
SKULL JOINTS:
Most of the joints of the skull are immovable and fibrous type these are known
as SUTURES.
Except of Temporomandibular joint which permits free movements
In adults, the bones are interlocked and the sutures cannot open up.
In old age, the sutures are gradually obliterated by fusion of the adjoining
bones.
The fusion begins on the inner surface of the skull between the age of 30 & 40
years; and on outer surface between 40-50 years.

16. ANATOMICAL POSITION OF SKULL
The skull can be placed is proper
orientation by considering any one of the
two planes:
 REID’S BASE LINE – A horizontal line
obtained by joining the infraorbital
margin to the centre of the external
acoustic meatus i.e. auricular point.
 THE FRANKFURTS HORIZONTAL PLANE – Is
obtained by joining the infraorbital
margin to the upper margin of the
external acoustic meatus

17.  FACIAL SKELETON-
It is composed of 14 bones.

18. EXTERIOR OF THE SKULL
 NORMA VERTICALIS
 NORMA FRONTALIS
 NORMA LATERALIS
 NORMA OCCIPITALIS
 NORMA BASALIS

19. Norma
verticalis

20.  “Superior view of the Skull”
• Oval in shape
• Wider posteriorly than anteriorly
 Visible bones:
1. Anteriorly Frontal bone
2. Posteriorly Occipital bone
3. Parietal bone on each side

21.  Visible sutures
1. Coronal suture - Placed between the frontal
bone and two parietal bones.
2. Sagittal suture - Placed between the two
parietal bones.
3. Lambdoid suture - Lies posteriorly between
the occipital and two parietal bones.
4. Metopic suture - Vertical suture placed
between the frontal bone
-occasionally present
- It separates the two half of
frontal bone & it fuses at 6
years of age

22. Other features
1. Vertex - highest point on the sagittal
suture.
2. Bregma - meeting point between the
sagittal and coronal suture.
3. Lambda - meeting point between the
sagittal and lambdoid suture
4. Parietal eminence - common site of fracture
of skull
5. Parietal foramen - transmits an emissary
vein
6. Obelion - on sagittal suture between the
two parietal foramina

23. NORMA
OCCIPITALIS

24.  NORMA
OCCIPITALIS
 “Posterior view of the skull”
• Convex upwards, flattened below
 Visible bones
1. Posterior part of Parietal bone
2. Occipital bone
3. Mastoid part of Temporal bone
 Visible sutures
1. Lambdoid suture
2. Occipitomastoid suture
3. Temporo-parietal suture
4. Posterior part of Sagittal suture

25.  Other features
1. Lambda, Parietal foramina & obelion is seen
2. External occipital protuberance – prominent
point is called Inion.
 Attachment- Upper part: Trapezius muscles
- Lower part: ligamentum nuchae
1. Highest nuchal line - begin from the upper part
of protuberance.
 Attachment- Medial: Epicranial aponeurosis
-Lateral: occipital belly of
occipitofrontalis muscle.
4. Superior nuchal line – junction of head and
neck
 Attachment- Medial 1/3: Trapezius
- Lateral: Sternocleidomastoid
muscles
5. Mastoid foramen – transmits an emissary vein &
meningeal branch of occipital artery

26. NORMA
FRONTALIS

27.  “Anterior view of the skull”
 Visible bones
1. Frontal bone- forms the forehead
2. Right and left Maxilla
3. Right and left Nasal bones
4. Zygomatic bones
5. The Mandible forms the lower jaw.

28.  Visible Sutures
1. Internasal
2. Frontonasal
3. Nasomaxillary
4. Lacrimomaxillary
5. Frontomaxillary
6. Intermaxillary
7. Zygomaticomaxillary
8. Zygomaticofrontal

29.  Frontal region of Norma frontalis:
1. Superciliary arch – better marked in males
than females.
2. Glabella- connecting the two superciliary
arches
3. Nasion – median point of the root of the
nose.
4. Frontal tuber or eminence – elevation above
the superciliary arch
- it is more prominent in females & in
children.

30.  Orbital openings:
- Quadrangular in shape
1. Supraorbital margin – formed by frontal
bone
2. Infraorbital margin – formed by zygomatic
and maxilla
3. Medial orbital margin – ill defined and
formed by frontal bone & lacrimal crest of
maxilla
4. Lateral orbital margin – formed mostly by
zygomatic bone

31.  Anterior bony aperture of the nose :
- pear shaped , being wide below &
narrow above
Boundaries
Above – lower border of the nasal
bone
Below – nasal notch of the body of
the maxilla
Features :
1. Rhinion is the lowermost point of the
internasal suture
2. Anterior nasal spine is a sharp
projection in the median plane
3. Internasal suture

32.  Lower part of the face :
 Maxilla-
1. Nasal notch
2. Anterior nasal spine
3. Infraorbital foramen
4. The incisive fossa
5. Canine fossa
 Process of Maxilla:
1. Frontal process of maxilla
2. Zygomatic process of maxilla
3. Alveolar process of maxilla

33.  Zygomatic bone
- forms the prominence of the
cheek
- Zygomaticofacial foramen is
seen
 Mandible
- forms the lower jaw
- Upper border or alveolar arch
- Lower border or base
- Middle point of the base is called gnathion.
- Anterior surface of the mandible represents
the symphysis menti, mental protuberance,
- Mental foramen below the interval between
the 2 premolar teeth

34.  STRUCTURES PASSING THROUGH
FORAMINA
 Supraorbital foramen – Supraorbital
nerves & vessels
 External nasal nerve emerges between
the nasal bone & upper nasal cartilage
 Infraorbital foramen – Infraorbital nerve
& vessels
 Mental foramen – Mental nerve and
vessels
 Zygomaticofacial foramen –
Zygomaticofacial nerve & vessels

35. NORMA
LATERALIS

36.  VISIBLE BONES –
“The skull viewed from the side”
1. Frontal
2. Parietal
3. Occipital
4. Temporal
5. Sphenoid
6. Zygomatic
7. Mandible & maxilla
8. Nasal
9. Lacrimal

37.  Visible features
1. Temporal line – two lines superior & inferior
-starts at the root of zygomatic process
and complete the circle by joining the posterior
root of zygomatic arch.
2. Zygomatic arch – formed by temporal process
of zygomatic bone in anterior 1/3 and the
zygomatic process of temporal bone posterior
2/3.
3. External acoustic meatus – just below the
posterior part of root of the zygoma
4. Mastoid process –downward projecting process
part of the temporal bone lies just behind the
external acoustic meatus
5. Suprameatal triangle – lies posterosuperior to
the meatus
- important surgical landmark for ear surgery

38. 6. Styloid process – needle like thin long projection
- situated anteromedial to the mastoid process
7. The pterion – is the region where the frontal,
parietal, temporal, and sphenoid bones join together.
It is located on the side of the skull, just behind the
temple.
8. The Asterion – is the point on the skull corresponding
to the posterior end of the parietomastoid suture.
9. Temporo -mandibular joint
10. The Temporal Fossa
Boundaries:
a. Above - Temporal line of frontal bone
b. Below - upper border of zygomatic arch laterally and
medially by infratemporal crest of sphenoid bone
c. Anterior wall- formed by zygomatic bone & parts of
frontal and sphenoid bones
d. Fossa- anterior part of the floor is crossed by H
shaped suture, this area is termed the pterion.
11. Infratemopral fossa

40.  ATTACHMENTS :
 Temporal facia is attached to the superior temporal line inferiorly attached to the
upper border of zygomatic arch.
 Temporalis muscles arises from the temporal fossa.
 Masseter muscle arises from the lower & medial surface of zygomatic arch.
 Sternocleidomastoid , splenius capitis and longissimus capitis attached to the lateral
surface of mastoid process
 Gap between the zygomatic arch & skull trasmitts -
a. Tendon of temporalis muscles
b. Deep temporal vessels
c. Deep temporal nerves

41.  VISIBLE SUTURES

42.  STRUCTURES PASSING THROUGH FORAMINA :
 Zygomaticotemporal foramen transmits zygomaticotemporal nerve &
artery.
 Mastoid foramen transmits emissary vein & meningeal branch of
occipital artery
 Tympanomastoid fissure transmits the auricular branch of vagus nerve

43. NORMA
BASALIS

44. “The skull viewed from the below”
Divided into 3 parts –
1. Anterior part
2. Middle part
3. Posterior part

45.  Anterior part of Norma Basalis
 Alveolar arch
 Hard palate
• Formation :
a. Anterior 2/3 – Palatine processes of maxilla
b. Posterior 1/3 – horizontal plates of palatine
bone
 Sutures :
• Cruciform suture made by inter maxillary &
inter palatine suture.

46.  Incisive fossa :
 Situated anteriorly in the median plane
 2 incisive canals, right and left
 Palatine crest :
 Curved ridge
 Begins behind the greater palatine
foramen & runs medially

47.  Middle part of Norma basalis
 Median area :
• Posterior border of the vomer
• Broad bar of the bone formed by part of sphenoid
and basilar part of the occipital bone
• Vomer – it separates two posterior nasal apertures
• Palatinovaginal canal
• Vomerovaginal canal

48.  Lateral area :
 2 parts of sphenoid bone –
pterygoid process
greater wing of sphenoid bone
 Pterygoid process :
-projects downwards behind the 3rd molar
-from the junction of greater wing and body of the
sphenoid
It divides into –
a. Medial pterygoid plate
b. Lateral pterygoid plate

49. A. Medial pterygoid plate :
• It has medial & lateral surface and a free
posterior border.
• Upper ends divides to enclose a triangular
depression called the scaphoid fossa
• Lower end of the posterior border is
prolonged downwards & laterally to form the
pterygoid hamulus.
B. Lateral pterygoid plate :
• It has medial & lateral surfaces and free
posterior border.
• Lateral surfaces forms the medial wall of
infratemporal fossa .
• Lateral & medial surface give origin to
muscles
• Pteygoid fossa present between two plates

51. • Greater wing of sphenoid bone :
- Pentagonal in shape
- Postero-lateral angle, it shows the sharp spine
projecting inferiorly called spine of shenoid
which gives attachment to the
sphenomandibular ligament
- Along the posteromedial margin, the surface is
pierced by the following foramina –
1. Foramen ovale – large & ovale in shape
2. Foramen spinosum – small & circular in
shape
3. Foramen of Vesalius – situated between the
foramen ovale & scaphoid fossa.
4. Canaliculus innominatus – situated between
the foramen ovale & foramen spinosum

52. • Carotid canal :
- A circular opening within the petrous temporal bone
- ICA enters the bone through carotid canal
- Carotid sheath applied at its margins.
• Foramen lacerum :
- Short wide canal ,1 cm long
• Tegmen tympani :
- A part of petrous temporal bone
- Present in the middle cranial fossa
• The tympanic plate :
- Triangular curved plate
- Lies between the petrous & the squamous parts.

55. FORAMINA STRUCTURES PASSING
5) FORAMEN SPINOSUM
(A) Middle meningeal artery.
(B) The meningeal branch of mandibular nerve or
nervous spinosus.
(C) Posterior trunk of middle meningeal vein.
6) FORAMEN MAGNUM
WIDER POSTERIOR PART:
(a) lowest part of medulla oblongata.
(b) three meninges.
THROUGH SUBARACNOID SPACE:
(a) Spinal accessory nerve.
(b) vertebral arteries.
(c) sympathetic plexus around the vertebral
arteries.
(d) posterior spinal arteries.
(e) anterior spinal artery.
THROUGH NARROW ANTERIOR PART:
(a) apical ligament of dense.
(b) vertical band of cruciate ligament.
(c) membrana tentoria.

56. FORAMEN STRUCTURES PASSING
7) JUGULAR FORAMEN
ANTERIOR PART
(a) Inferior petrosal sinus.
(b) meningeal branch of ascending
pharyngeal artery.
MIDDLE PART
(a) IX,X,XI cranial nerves.
POSTERIOR PART
(a) Internal jugular vein.
(b) meningeal branch of occipital artery.
8) HYPOGLOSSAL OR ANTRIOR
CONDYLAR CANAL
(a) Hypoglossal nerve
(b) Meningeal branch of hypoglossal
nerve.
(c) Meningeal branch of ascending
pharyngeal artery.
(d) Emissary vein connecting the
sigmoid sinus with internal jugular
vein.
9) FORAMEN ROTUNDUM Maxillary nerve

57. FORAMINA STRUCTURES PASSING
10) STYLOMASTOID FORAMEN Facial nerve
11)PETROTYMPANIC FISSURE
(a) Chorda tympanic nerve
(b) Anterior tympanic artery.
12) CAROTID CANAL
(a) Internal carotid artery.
(b) Venous and sympathetic plexus around the arteries.
13) EMISSARY SPHENOIDAL FORAMEN Emissary vein connecting cavernous sinus with the pterygoid
plexus of vein.

58.  Posterior part of Norma basalis is again divided into TWO parts
–
A. Median part
B. lateral part
 MEDIAN AREA : The median area involves
(a) Foramen Magnum
(b) External occipital crest
(c) External occipital protuberance

59.  The superior nuchal lines begins at external occipital protuberance & the
inferior nuchal lines at middle of the crest. Both of them curves laterally
backwards then laterally and forwards.

60. (A) FORAMEN MAGNUM:-
- It is the largest foramen of the skull
- It opens upwards into posterior cranial fossa and
downwards into vertebral canal
- It is oval in shape being wider behind than in front where
it is overlapped on each sides by occipital condyles
(B) THE EXTERNAL OCCIPITAL PROTRUBERANCE:-
- It is the projection located at the posterior end of the
crest
- It is easily felt in the livings in the midline , at a point
where back of neck becomes continuous with the scalp.

61. LATERAL AREA :
The lateral area shows the:
(a) CONDYLAR part of occipital bone.
(b) SQUAMOUS Part of occipital bone.
(c) The JUGULAR Foramen between occipital and petrous temporal bone.
(d) The STYLOID process of temporal bone.
(e) The MASTOID process of temporal bone.

62. (A) CONDYLAR OR LATERAL PART : It
presents
(i) Occipital condyles – oval in shape and
are situated on each side of anterior
part of the foramen magnum
-There long axis is directed forwards and
medially.
- They articulates with superior articular
facets of the ATLAS vertebra to form
ATLANTO OCCIPITAL joint.
(ii) Hypoglossal or anterior condylar canal
- Pierces the bone anterosuperior to the
occipital condyle and is directed
laterally and slightly forwards.

63. (iii) The POSTERIOR CONDYLAR CANAL :
- It is occasionally present in the floor of the condylar fossa and present
behind the occipital condyles.
- Superiorly it opens into sigmoid sulcus.
(iv) The JUGULAR PROCESS :
- The jugular process of occipital bones lies lateral to the occipital
condyles and forms posterior boundaries of the jugular foramen.

64. (B) THE SQUAMOUS PART :
- It is marked by superior and inferior nuchal lines.
(C) JUGULAR FORAMEN :
- It is large and elongated and its long axis is directed
forwards and medially . It is placed at the posterior end of the petro-occipital
suture.
- At the posterior end of foramen its anterior wall is
hollowed out to form jugular fossa which lodges superior bulb of internal
jugular vein . The fossa is larger on right side than on left.
- The lateral wall is pierced by minute canals , the Mastoid
Canaliculus.
- Near medial end of foramen there is jugular notch.

65. - At apex of the notch there is opening that leads to cochlear
canaliculus.
-Tympanic canaliculus opens on or near the thin edge of the bone
between the Jugular fossa and lower end of carotid canal.
(D) THE STYLOID PROCESS OF TEMPORAL BONE :
- The styloid mastoid foramen is situated posterior to the root
of styloid process, at the anterior end of the mastoid notch.
(E) THE MASTOID PART OF TEMPORAL BONE:
- Large conical projection located posterolateral to the
stylomastoid foramen. It is directed downwards and forwards . It forms lateral
wall of mastoid notch.

66. INTERIOR OF
SKULL

68.  Interior of base of skull presents natural
subdivisions into
Anterior,
Middle and
posterior cranial fossae.
 ANTERIOR CRANIAL FOSSA:-
BOUNDRIES:-
1) Anteriorly and on sides- by frontal bone
2) Posteriorly- it is separated from the
middle cranial fossa by the free posterior border
of lesser wing of sphenoid, the anterior
clenoid process and the anterior margin of
sulcus chiasmaticus.

70.  FLOOR:-
(A) In the MEDIAN PLANE it is formed anteriorly by the cribriform plate of
ethmoid bone.
(B) POSTERIORLY by the superior surface of the anterior part of the body
of sphenoid or jugum sphenoidale.
(C) On each sides floor is formed mostly by the orbital plate of frontal
bone and is completed posteriorly by lesser wing of sphenoid.
OTHER FEATURES: -
1.The CRIBRIFORM plate of ethmoid
bone separates the anterior cranial
fossa from the nasal cavity.

71.  (a) the anterior margin articulates with frontal bone at
frontoethmoidal suture which is marked in median plane by
foramen caecum.
 (b) the posterior margins articulate with jugum sphenoidale. At the
posterolateral corners we see posteroethmoidal canals.
 (c) the lateral margins articulate with the orbital plate of the
frontal bone.
- Anteriorly the cribriform plate has the midline projection called
as CRISTA GALLI. On each side of which there is foramina through
which anterior ethmoidal nerves and vessels pass to the nasal cavity
 - The plate is also perforated by numerous foramina for passage of
olfactory nerve rootlets.

72.  2. JUGUM SPHENOIDALE separates anterior crania fossa from the
sphenoidal sinuses.
 3. The ORBITAL PLATE of the frontal bone separates the anterior cranial
fossa from the orbit.
 4. The LESSER WING OF SPHENOID is broad medially where it is continous
with jugum sphenoidale and tapers laterally. The free posterior border
fits in the stem of lateral sulcus of brain.
 It ends medially as a prominent projection ANTERIOR CLENOID PROCESS
 INFERIORLY- the posterior border forms the upper boundary of SUPERIOR
orbital fissure.
 MEDIALLY- it is connected to body of sphenoid.by anterior and posterior
roots which encloses OPTIC CANAL.

73. THE MIDDLE CRANIAL FOSSA
 It is deeper than anterior cranial fossa and is shaped like butterfly, being narrow and shallow
in middle and wide and deep on sides.

75.  BOUNDARIES:
(A) ANTERIOR- (1) Posterior border of lesser wing of
spheniod
(2) anterior clenoid process.
(3) anterior margin of sulcus chiasmaticus.
(B) POSTERIOR- (1) Superior border of petrous temporal
bone
(2)dorsum sella of sphenoid .
(C) LATERAL – (1) Greater wing of sphenoid
(2) anteroinferior angle of parietal bone
(3) squamous temporal bone in middle.

76. FLOOR:-
- floor is formed by body of sphenoid in the median
region and greater wing of sphenoid , squamous
temporal bone and anterior surface of petrous
temporal bone on each side.
OTHER FEATURE
MEDIALLY -
(A) sulcus chiasmaticus
(B) optic canal
(C) sella tursica
LATERALLY -
(A) Superior orbital fissure
(b) foramen rotundum , foramen ovale , emissary
sphenoidal foramen, foramen lacerum .
(c) anterior surface of petrous temporal bone
presents- tegmen tympani, arcurate eminence.

77. POSTERIOR CRANIAL FOSSA
 It is largest and deepest of the three cranial fossae . It consist of
hindbrain which consist cerebellum behind and the pons and medulla
in front.

78.  BOUNDARIES :-
(A) ANTERIOR – (1) Superior part of petrous temporal bone
(2) dorsum sellae of sphenoid
bone.
(B) POSTERIOR- (1) Squamous part of occipital bone.
On each side-
(a) mastoid temporal bone
(b) mastoid angle of parietal bone
 FLOOR:-
(A) MEDIAN AREA- (1) Sloping area behind the dorsum sellae or clivus in
front.
(2) foramen magnum in middle
(3) squamous occiptal behind.

79. (B) LATERAL AREA:- (1) Condylar or lateral part of occipital bone.
(2) posterior surface of petrous temporal bone.
(3) mastoid temporal bone
(4) mastoid angle of the parietal bone.

81.  OTHER FEATURES:-
 (I) MEDIAN AREA:- (a)clivus- sloping surface in front of foramen magnum.
(b) foramen magnum
(c) internal occipital crest, internal occipital protuberance ,
transverse sulcus
 (II) LATERAL AREA:- (a) condylar part shows- jugular tubercle, hypoglossal
canal.
(b) posterior surface of petrous temporal bone shows-
internal acoustic meatus, orifice of aqueduct of the vestibule, subarcurate fossa.
(c) jugular foramen.
(d) mastoid part of temporal bone.

82. TO BE CONTINUED …