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Frontal bone

Superior view, anterior to bottom

Frontal bone

Lateral view, anterior to left

Frontal bone

Inferior view, anterior to top

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nium. The external surface of each parietal bone is slightly convex while the internal surface is concave

and marked with impressions from meningeal vessels. The inferior border forms a beveled articular surface, while the superior, anterior, and posterior borders form deeply denticulate articular surfaces. The

bone consists of inner and outer laminae of compact bone sandwiching a layer of trabecular bone, the

diploë. Each parietal bone articulates with fi ve bones.

The parietal bones are large quadrilateral bones forming the greater

part of the roof and sides of the craCranial Bones – Parietal

 1 Groove for sigmoid sinus

 2 Groove for superior sagittal sinus

 3 Grooves for middle meningeal artery

 4 Superior temporal line

 5 Inferior temporal line

 6 Parietal tuber

 7 Squamosal border

 8 Occipital border

 9 Frontal border

10 Sagittal border

 11 Frontal angle

12 Occipital angle

13 Sphenoid angle

14 Mastoid angle

15 Parietal foramen

Left parietal bone

Medial view, anterior to right

Left parietal bone

Lateral view, anterior to right

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2

3

8

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14

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Left parietal bone

Anterior view

Left parietal bone

Posterior view

Left parietal bone

Inferior view, anterior to right

Left parietal bone

Superior view, anterior to left

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behind it has an oval to round shape. The bone has four distinct regions. The squamous portion is the internally concave posterosuperior plate and forms the greater part of the bone. The thick quadrilateral basioccipital, or basilar part, contributes to the base of the cranium anterior to the foramen magnum. Lateral

to this and converging with the squama are the two condylar parts or exoccipitals. Together the four regions of the bone form the borders to the large circular opening, the foramen magnum, which provides

passage for the spinal cord between the cranial vault and the spinal canal. The occipital bone articulates

with six bones.

The occipital bone forms the

greater part of the posterior and

inferior cranium. Viewed from

Cranial Bones – Occipital

 1 Foramen magnum

 2 Clivus

 3 Pharyngeal tubercle

 4 Squamous part

 5 Mastoid border

 6 Lambdoid border

 7 Occipital condyle

 8 Condylar canal

 9 Hypoglossal canal

10 Condylar fossa

 11 Jugular tubercle

12 Jugular notch

13 Jugular process

14 External occipital protuberance

15 Superior nuchal line

16 Inferior nuchal line

17 Internal occipital protuberance

18 Groove for transverse sinus

19 Groove for occipital sinus

20 Groove for superior sagittal sinus

21 Cerebral fossa

22 Cerebellar fossa

Occipital bone

Posterior view

Occipital bone

Anterior view

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Occipital bone

Inferior view, anterior to bottom

Occipital bone

Lateral view, anterior to right

Occipital bone

Superior view, anterior to bottom

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the bone is the thin lateral plate that contributes to the lateral wall of the cranium. It projects anteriorly

as the zygomatic process and forms the mandibular fossa for the temporomandibular joint. The styloid

part is represented by the styloid process. This projection of bone arises from the upper elements of the

second pharyngeal arch. The petrous part forms the thick pyramidal base of the bone. It begins posterior to the external acoustic meatus as the mastoid process and ends where it forms a junction with the

basi-occipital and greater wing of the sphenoid. The name petrous describes its rock-like appearance.

This is the thickest part of the temporal bone. It arises from the otic capsules that stabilize the delicate

internal ear structures. The mastoid is the posterolateral protuberance of the petrous portion that is easily

palpable just posterior to the ear. The tympanic part of the temporal bone is the ring-like plate that forms

the walls of the external acoustic meatus. Each temporal bone articulates with fi ve bones.

The temporal bone is a complex bone with fi ve distinct

parts. The squamous part of

Cranial Bones – Temporal

Left temporal bone

Medial view, anterior to right

Left temporal bone

Lateral view, anterior to left

 1 Petrous part

 2 Mastoid process

 3 Mastoid notch

 4 Groove for sigmoid sinus

 5 Carotid canal

 6 Apex of petrous part

 7 Musculotubal canal

 8 Tegmen tympani

 9 Hiatus for greater petrosal nerve

10 Hiatus for lesser petrosal nerve

 11 Trigeminal impression

12 Internal acoustic meatus

13 Mastoid canaliculus

14 Tympanic canaliculus

15 Styloid process (broken)

16 Stylomastoid foramen

17 Jugular notch

18 Tympanic ring

19 External acoustic meatus

20 Greater tympanic spine

21 Lesser tympanic spine

22 Squamous part

23 Zygomatic process

24 Mandibular fossa

25 Articular tubercle

26 Petrotympanic fissure

27 Tympanomastoid fissure

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Left temporal bone

Superior view, anterior at top

Left temporal bone

Posterior view

Left temporal bone

Anterior view

Left temporal bone

Inferior view, anterior at bottom

1

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terfl y. Like it name suggests, it is wedged into the center of the cranium where it articulates with twelve

neighboring bones and contributes to much of the cranial base. It is divisible into four principal components — the body, greater wings, lesser wings, and pterygoid processes. With the calvaria removed the

bone is visible from any view. This bone plays a prominent role at the base of the skull. It supports the

brain, serves to protect the optic stalks and capsules, provides passage for many vessels and nerves

entering and leaving the skull, and forms a sinus cavity that communicates with the nasal cavity.

The sphenoid bone is a complex bone that has the spread

-winged appearance of a butCranial Bones – Sphenoid

 1 Jugum

 2 Sella turcica

 3 Tuberculum sellae

 4 Hypophysial fossa

 5 Dorsum sellae

 6 Posterior clinoid process

 7 Middle clinoid process

 8 Carotid sulcus

 9 Sphenoidal crest

10 Sphenoidal rostrum

 11 Sphenoidal sinus

12 Sphenoidal concha

13 Lesser wing

14 Optic canal

15 Anterior clinoid process

16 Superior orbital fissure

17 Greater wing

18 Infratemporal crest

19 Orbital surface

20 Foramen rotundum

21 Foramen ovale

22 Foramen spinosum

23 Spine of sphenoid bone

24 Lateral plate of pterygoid process

25 Medial plate of pterygoid process

26 Pterygoid notch

27 Pterygoid fossa

28 Scaphoid fossa

29 Vaginal process

30 Pterygoid hamulus

31 Pterygoid canal

Sphenoid bone

Anterior view

Sphenoid bone

Posterior view

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Sphenoid bone

Inferior view, anterior at top

Sphenoid bone

Superior view, anterior at top

Sphenoid bone

Lateral view, anterior to left

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60

walls of the nasal cavity, orbit, oral cavity, and maxillary sinus. The maxillary sinus is the hollow central

cavity within the large body of the maxilla. Four variable-shaped processes project from the maxillary

body. The processes are the posterolateral zygomatic process, the medial projecting palatine process,

the arched inferior process called the alveolar, and the superiorly projecting frontal process. Each

maxilla articulates with nine bones.

Cranial Bones – Maxilla

 1 Orbital surface

 2 Infra-orbital groove

 3 Infra-orbital foramen

 4 Anterior nasal spine

 5 Canine fossa

 6 Maxillary tuberosity

 7 Lacrimal groove

 8 Maxillary sinus

 9 Greater palatine groove

10 Frontal process

 11 Zygomatic process

12 Palatine process

13 Incisive canal

14 Alveolar process

15 Interalveolar septum

Left maxilla

Anterior view

Left maxilla

Posterior view

The maxillae are large, paired

bones that unite to form the upper

jaw. They also contribute to the

3

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