The cranial bones include the frontal, sphenoid, ethmoid, temporal, parietal and occipital bones. Together they form the skull, which protects the brain and provides attachment points for muscles. The sphenoid bone is butterfly-shaped and located in the middle of the skull. It contains openings for cranial nerves and blood vessels. The temporal bones each contain four regions and form parts of the skull and ear. Sutures are fibrous joints between cranial bones that fuse during development and increase skull strength.

1. CRANIAL BONES
-Anatomic Description
-Joints
-Their Functions

2. The skull comprises in 18 main elements.
A bony structure that supports the face and forms
a protective cavity for the brain.
The bones of the skull can be divided into two groups:
those of the cranium (which can be subdivided the skullcap
known as the calvarium, and the cranial base) and those of
the face.
Main Features

3. Anatomically, the cranium can be subdivided into a roof (known as the calvarium), and a base:
Calvarium: Comprised of the frontal, occipital and two parietal bones.
Cranial base: Comprised of six bones – the frontal, sphenoid, ethmoid, occipital, parietal and temporal bones.
These bones are important as they provide an articulation point for the 1st cervical vertebra (atlas), as well as the
facial bones and the mandible (jaw bone).

4. SPHENOID BONES

5. Sphenoid Bones
It is a butterfly shaped cranial bone that is located in the
middle of the skull between the frontal and temporal
bones.
(os sphenoidale; Gr., sphen – wedge + eidos – form)
Markings:
-Body: (corpus sphenoidalis)
It contains the sphenoid sinuses
and a large depression for the
pituitary gland.

6. -(ala minor
sphenoidalis) is the
smaller of two wing-like
lateral extensions that
arise from the sides of the
sphenoid body.
-(ala major
sphenoidalis) is the larger
of two wing-like lateral
extensions that arise from
the sides of the sphenoid
body.
-Orbital surface of the
greater wing (facies orbitalis
sphenoidalis) is the smooth,
anterior portion the greater
wing.
Optic canal or foramen (canalis
opticus or foramen opticum
sphenoidalis) is an opening in
the lesser wing that transmits
the optic nerve and ophthalmic
artery.

7. (Fissura orbitalis superior
sphenoidalis) is an narrow
opening between the lesser
and greater wings in the
posterior orbit.
It is a round hole in the
anteromedial portion of the
greater wing. It gives passage to
the maxillary nerve branch of the
trigeminal nerve.
(foramen ovale sphenoidalis) is an oval hole in the posterior
portion of the greater wing.
It is the passageway for the mandibular nerve ( a branch of
the trigeminal nerve), accessory meningeal artery, lesser
petrosal nerve, and emissary veins.

8. It is a small opening posterior to the foramen
ovale that transmits the middle meningeal
artery and the meningeal branch of the
mandibular nerve.
(sulcus chiasmaticus or sulcus prechiasmaticus
sphenoidalis) is a narrow, transverse depression that
runs between the optic canals.

9. (processus clinoideus anterior sphenoidalis) is a posterior projection
from each lesser wing.
(sella turcica sphenoidalis; L. Turkish saddle) is a depression on the
upper part of the body.
They are attachment sites for the tentorium cerebelli (dura
mater), which separates the cerebellum from the inferior
occipital lobes of the brain.
It houses the pituitary gland (hypophysis) and consists of
the hypophyseal fossa, dorsum sellae, tuberculum sellae,
and posterior clinoid processes.

10. (fossa hypophysialis
sphenoidalis) is the
depression in which the
pituitary gland sits.
(tuberculum sellae
sphenoidalis) is the raised
anterior edge of the sella
turcica, which is located
just posterior the
chiasmatic groove.
(dorsum sallae
sphenoidalis) is the square-
shaped posterior wall of
the sella turcica.
(processus clinoideus posterior
sphenoidalis) is a small, lateral
extension from each side of the
dorsum sellae.

11. (processus pterygoideus sphenoidalis) is an inferior extension
from the junction of the sphenoid body and greater wing.
Lateral pterygoid plate (lamina lateralis processus
pterygoidei sphenoidalis) is lateral of two plates that
form the pterygoid process.
It is the attachment point for the lateral and medial
pterygoid muscles, which move the mandible while
chewing.
Each pterygoid process consists of two, thin, vertical plates
(Gr., pterygodes – wing shaped).

12. (lamina medialis processus pterygoidei sphenoidalis) is
the narrower, longer plate of pterygoid process.
(hamulus pterygoideus sphenoidalis) is a hook-like
inferior extension of the medial pterygoid plate.
Its medial surface gives support to the posterior opening
of the nasal cavity.

14. The flattened squamous part forms the superior region of the
bone that helps protect the sides of the brain (temporal
lobe).
TEMPORAL BONES
It is anatomically divided into four regions called the squamous, mastoid, temporal, and petrous parts.

15. Markings of
temporal bone
(pars squa-mosa: squama temporalis)
is the smooth, thin, superior portion of
the bone that forms the lower lateral
cranial wall.
(processus zygo-maticus temporalis) is a
narrow, anterior extension from the inferior
portion of the temporal squama.
It joins with the temporal process of the zygomatic bone
to form the zygomatic arch (or check bone).

16. (pars tympanica tem-poralis) is the region
of the temporal bone that surrounds the
ear canal.
(meatus acusticus externus
temporalis) is a prominent canal (the
ear canal) in the tympanic part of the
temporal bone.
It is located inferior to squamous part and
anterior to the mastoid part of the bone.

17. (processus styloideus
temporalis) is a narrow
inferior extension from the
bottom surface of the
tympanic part of the
temporal bone.
(pars petrosa temporalis) is a
pyramid-shaped portion of the
temporal bone that projects
medially and anteriorly from the
squamous part. It forms a narrow
mass between the sphenoid
bone (anterior) and the occipital
bone (posterior).

18. (meatus acusticus internus temporalis) is a canal along the
posteromedial surface of the petrous part.
(canalis caroticus tem-poralis) is a prominent hole on
the inferior surface of petrous part of the temporal
bone, just anterior to jugular foramen. It gives
passage for the internal carotid artery to enter the
base of the skull.
It gives passage to the facial and vestibulocochlear
(auditory) nerves and the labyrinthine artery (an internal
auditory branch of the basilar artery).

19. (pars mastoidea
temporalis) is the thick,
roughened, posterior
portion of the temporal
bone that is located
behind the ear.
(processus mastoideus
temporalis) is a pyramidal or
conically shaped protrusion
from the inferior surface of
mastoid part of the temporal
bone, just posterior to external
auditory meatus.

20. (incisura mastoidea temporalis) is a
narrow, deep depression on the
medial side of the mastoid process.
(foramen stylo-mastoideum
temporalis) is a small hole on the
inferior surface of the petrous part
of the temporal bone, in the region
between styloid and mastoid
processes.
It is an attachment point for the
digastric muscle that moves the hyoid
bone and opens the mouth (or
depresses the mandible).

21. It transmits the emissary vein(s) from the sigmoid sinus
and a branch of the occipital artery to the dura mater.
(foramen mastoideum temporalis)
Is a hole of variable size and position that is
located on the inferior surface of the skull,
posterior to mastoid process.

22. OCCIPITAL
BONES

23. Occipital Bone
-Along with its inferior and internal surfaces is the prominent
foramen magnum.
-The broad, curved region superior to the foramen magnum is
called the squamous part (= squama occipitalis) of the bone.
Anterior to the foramen magnum is the basilar part and to the
sides are the lateral parts.
FEATURES
-The spinal cord passes through.
-The occipital condyles , which are rounded surfaces at the base of the occipital bone, articulate with
the atlas (the first vertebra of the spine), enabling movement of the head relative to the spine.
-Mechanical protection of the brain, which is a function that the occipital bone performs in conjunction
with other bones of the skull.
FUNCTIONS

24. Markings of the Occipital Bone
Elevation (larger in men) near the
center of the squamous part.
Attachment point for ligamentum
nuchae and trapezius muscle.
A ridge that runs horizontally from
either side of the external occipital
protuberance.
Attachment point for several
muscles that control the position
of the head and neck.

25. A slight ridge above the superior nuchal line; attachment point for
galea aponeurotica (connective tissue membrane that attaches the
occipitalis and frontalis portions of occipitofrontalis muscle).
A slight vertical ridge that runs from external
occipital protuberance to foramen magnum.
Attachment point for ligamentum nuchae.

26. Ridge that runs horizontally from
both sides of the median nuchal
line below the superior nuchal
line.
Attachment point for
several muscles that control
the position of the head
and neck.
Large, oval opening at
the base of the skull.
Passageway for spinal
cord.

27. Prominent, rounded elevation located to the side of the
foramen magnum; articulates with the superior articular facet
of the atlas (1st) vertebra.
Passageway for internal jugular vein and
glossopharyngeal, vagus, and accessory nerves.
Large, irregular opening along the junction of
occipital and temporal bones.

28. Hole located in basilar part of bone superior to occipital
condyle.
Passageway for the hypoglossal nerve that
controls movement of tongue.
elevation at the center of the cruciform eminence
(= vertical and horizontal grooved ridges that divide
internal surface of occipital bone into four fossa).

29. Ridge that runs vertically from internal occipital protuberance to
foramen magnum.
Indentations running horizontally from internal occipital
protuberance.
Attachment point for connective tissues (falx cerebelli) that
anchors the brain.
Also serve as attachment points for tentorium cerebelli
(= dura mater that runs between the cerebellum and
occipital lobes of the brain).
Provide channels for transverse sinuses that drain venous
blood from the brain to jugular foramen.

31. -It forms the forehead and extends down to also form the
upper surfaces of the orbits
-It also forms the anterior roof of the skull.
-Mechanical protection of the front (anterior) part of brain.
-The shape of the frontal bone contributes to defining the
shape of the head and face, and therefore the person's
visual identity.
FEATURES
LOCATION
FUNCTION

32. Markings of the
Frontal Bone
-(arcus superciliaris frontalis) is a smooth,
arched, elevation above the orbit, which forms
the eyebrow ridge.
-(glabella frontalis) is a smooth prominence located above
the nasal bones (or nose) and between the superciliary
arches (or eyebrow arches).

33. (incisura supraobitalis frontalis; foramen supra-orbitae
frontalis) is a notch or small hole located along the
superior margin of the orbit.
(facies orbitalis frontalis) is a
horizontal extension that forms the
roof of the orbit and nasal cavity.
It serves as a passageway for the supraorbital vessels and
nerve

34. (processus zygomaticus frontalis) is an inferior
extension of the squamous part of the frontal bone
that joins with the frontal process of the zygomatic
bone.
(sinus frontalis) is a large cavity located above the orbit
and deep to the superciliary arch.

35. Ethmoid
Bones

36. (Gr., ethmos – sieve) is a spongy, cuboid-shaped cranial
bone located at the top of the nasal cavity and between
the two orbits.
FEATURES
It primarily consists of two lateral masses (containing the
ethmoid air cells or ethmoid sinuses) and several
projections that extend into the nasal cavity and cranial
floor.
-It forms part of the nasal cavity and the orbits.
-It is the main mechanical support structure of the nasal
cavity.
FUNCTIONS

37. Markings of the
Ethmoid Bone
(or orbital lamina, lami-na
papyracea) – thin plate along
the lateral margin of the
ethmoid labyrinth (or lateral
mass); forms part of the medial
wall of the orbit.
thin vertical plate that extends
down into nasal cavity;
articulates with vomer bone to
form bony nasal septum.

38. (or superior con-cha) –
short, thin, plate that
extends down into the nasal
cavity just above the middle
turbinate; serves same
functions as middle
turbinate.
(or middle concha, plural =
conchae) – thin plate that
extends down into nasal cavity
lateral to perpendicular plate;
covered with mucous membrane,
which warms, moistens, and
cleans inhaled air.

39. (or ethmoid labyrinth) – region of bone lateral to perpendicular plate;
contains many mucous-lined air cells (the ethmoid sinuses) that open
into nasal cavity.
(L., cribum = sieve) – a horizontal plate (or lamina) in
cranial floor and roof of nasal cavity that articulates with
the frontal bone.

40. (or L. crest of the cock) – thin vertical plate that extends up
from cribiform plate; attachment point for the falx cerebri
(= part of the connective tissues that surround and protect
the brain).

41. PARIETAL
BONES

42. FEATURES
-(os parietal; L., paries – wall) is a large, thin, four-sided
cranial bone that makes up much of the top and sides of
the cranium.
-It articulates with the frontal bone, the temporal bone, the
occipital bone and the other parietal bone.
-The parietal bones form the posterior roof of the skull
-The parietal bones provide mechanical protection of the brain, which
is a function they perform in conjunction with other bones of the skull.
FUNCTION
-The external surface is broadly convex and has few
anatomical markings. The internal surface is concave and
also lacks prominent markings.

43. Markings of the Parietal Bone
(linea temporalis superior parietalis) is the upper of the
two lines that arc across the lateral surface of the parietal
bone. It serves as an attachment point for the temporal
fascia that covers the temporalis muscle.
(linea temporalis inferior parietalis) is the lower of the two
lines that arc across the lateral surface of the parietal
bone. It is an attachment point for the temporalis muscle.

44. (foramen parietale) is a small hole found along the
posterior aspect of the bone, next to the sagittal suture.
It is the passageway for an emissary vein that drains
blood to the exterior of the skull from the superior
sagittal sinus. The foramen is not always present and
varies in size.
(eminentia parietalis; tuber parietale) is a
rounded elevation on the external surface
of the parietal bone. It is located near the
middle of the bone and marks the widest
point of the skull. This is the area where
ossification of the parietal bone began.

46. Sutures are a type of fibrous joint that are
unique to the skull. They are immovable, and
fuse completely around the age of 20.
The junction between the frontal and parietal bones.
Coronal Suture
The junction between the parietal and
temporal bones.
Squamousal Suture
The irregular interlocking edges of the bones attached
by these sutures contribute to the overall strength of the
joints and so and reduce the risk of fracture due to
impacts or other possible damage.
THEIR FUNCTIONS

47. The junction between the sphenoid and frontal bones.
The junction between the sphenoid and temporal bones.
Sphenofrontal Suture
Sphenosquamousal Suture

48. The junction between the parietal and temporal bones.
The junction between the occipital and temporal bones.
Parietomastoid Suture
Occipitomastoid Suture

49. The junction between the two parietal bones.
The junction between the parietal bones and the occipital
bone.
Sagittal Suture
Lambdoidal Suture

50. The junction between the parietal and temporal bones.
The junction between the occipital and
temporal bones.
Parietomastoid Suture
Occipitomastoid Suture

51. Cranial Bones
Main Features
Sphenoid Bones
Body
Lesser Wing
Greater wing
Optic Canal
Superior Orbital Fissure
Ovale Foramen
Foramen Rotundum
Foramen
Spinosum
Chiasmatic Groove
Anterior
Clinoid
Process
Sellae Turica
Hypophyseal
Fossa
Dorsum
Sellae
Tuberculum
Sellae
Posterior Clinoid
Process
Pterygoids
Temporal Bones
Squamous Part
Zygomatic Process
Tympanic Part
External Acoustic Meatus
Styloid Process Petrous Part
Mastoid Part
Mastoid Process
Mastoid Notch
Mastoid Foramen
Occipital Bones
External Occipital ProtuberanceSuperior Nuchal Line
Median Nuchal Line
Inferior Nuchal Line
Foramen Magnun
Occipital Condyle
Occipital Jugulare
Hypoglossal Canal
Internal Occipital Protuberance
Groove for
transverse Sinus Internal Occipital Crest

52. Ethmoid Bones
Orbital Plate
Perpendicular Plate
Middle Turbinate
Superior Turbinate
Lateral Mass
Cribriform Plate
Crista Galli
Parietal Bones
Superior Temporal Line
Inferior Temporal Line
Parietal Foramen
Parietal Eminence
Frontal Bones
Superciliary Arch
Glabella
Supraorbital Notch
Orbital Surface
Zygomatic Process Frontall Sinus