View of a Skull, 1489 by Leonardo Da Vinci

Kaan Yücel M.D., Ph.D. 26.11.2013 Tuesday

1.SKULL

skeleton of the head

cranium

22 bones excluding ossicles of the ear

1.SKULL

Mandible Lower jaw bone

1.SKULL

skeleton of the head

Neurocranium Viscerocranium facial skeleton

22 bones in the cranium

8 @ neurocranium

Frontal bone- single Occipital bone- single Parietal bones- paired Temporal bones- paired Sphenoid bone- single Ethmoid bone- single

neurocranium 1 roof (calvaria) 1 floor base (base of the skull) basicranium

CALVARIA TEMPORAL BONES PARIETAL BONES parts of the single frontal, sphenoid, & occipital bones

CRANIAL BASE mainly parts of the Sphenoid bone Temporal bones Occipital bone

BONES OF THE NEUROCRANIUM

FRONTAL BONE OS FRONTALE

FRONTAL BONE 1. Squama vertical portion

region of the forehead

2. Orbital portion frontal orbit/orbita frontalis horizontal portion

formation of roofs of the orbital & nasal cavities

Squama

ANTERIOR VIEW

supra-orbital margin of the frontal bone

angular boundary between squamous & orbital parts

superciliary arches superior to

supra-orbital margin & rim of the

orbit

prominence of these ridges

greater in males

glabella small depression between superciliary

arches

ANTERIOR VIEW

frontal eminences

in some

calvaria looks like a square

Medially frontal bone projects inferiorly forms part of the medial rim of the orbit.

Laterally zygomatic process of the frontal bone projects inferiorly forms upper lateral rim of the orbit. articulates with frontal process of the zygomatic bone.

ANTERIOR VIEW

In some adults Visible in the midline of the glabella Smooth, slightly depressed area between superciliary arches

a persistent frontal suture or remnant of it

ANTERIOR VIEW

INTERNAL VIEW

Sagittal sulcus

vertical groove @ upper part of the midline squama frontalis

Frontal crest

formed by the union of the edges of the sagittal sulcus

median bony extension of the frontal bone

Foramen cecum (blind hole)

@ the base of the frontal crest

Nasal process downward projection of the nasal part

of the frontal bone terminates as

nasal spine

Two parietal bones unite and form the sides & roof of the cranium. Each bone is irregularly quadrilateral in form.

PARIETAL BONES OS PARIETALE

PARIETAL BONES OS PARIETALE

Parietal eminence (tuber parietale)

an elevation near the centre of the convex and smooth external surface

Superior and inferior temporal lines

two curved lines crossing the middle of the bone in an arched direction

PARIETAL BONES OS PARIETALE

Parietal foramen small, inconstant aperture posteriorly in the parietal bone near sagittal suture

Situated at the sides and base of the skull. Contributes most of the lower portion of lateral wall of the cranium.

TEMPORAL BONES OS TEMPORALE

3 parts

1. Squamous part 2. Tympanic part 3. Petromastoid part

TEMPORAL BONES

contributes to lateral wall of the cranium articulates

anteriorly with greater wing of the sphenoid bone superiorly with parietal bone

Squamous part of the temporal bone

large flat plate, forms the anterior & superior parts of the temporal bone

Squamous part of the temporal bone

Zygomatic process

anterior bony projection from the lower surface of the squamous part of the temporal bone

Zygomatic arch zygomatic process of the temporal bone+temporal process of the zygomatic bone

Temporomandindibular joint

mandibular fossa

concave depression located inferiorly @ squamous portion Head of the mandible enters here! articular tubercle

downward projection of the anterior border of the mandibular fossa

Tympanic part of the temporal bone just below the origin of the zygomatic process

External acoustic opening (pore)

entrance to the external acoustic meatus (canal) leads to the tympanic membrane (eardrum).

Mastoid part of the temporal bone

most posterior part of the temporal bone

continuous with squamous part anteriorly

articulates with parietal bone superiorly occipital bone posteriorly.

Mastoid part of the temporal bone

mastoid process on the lateral aspect, cone-shaped projection from the inferior surface mastoid notch

medial aspect of the mastoid process

Petrous part of the temporal bone lateral to the basilar part of the occipital bone

between greater wing of the sphenoid anteriorly basilar part of the occipital bone posteriorly.

foramen lacerum apex of the petrous part forms one of the boundaries of this foramen.

opening for the carotid canal large circular opening posterolateral to the foramen lacerum

Petrous part of the temporal bone

Petrous part of the temporal bone Anterior surface

1. Arcuate eminence (Eminentia arcuata) @ centre of the anterior surface. 2. Tegmen tympani anterolateral to arcuate eminence,thin bony roof of the middle ear cavity.

tegmen (covering; covering, cover, protection)

Petrous part of the temporal bone Anterior surface

3. Groove for greater petrosal nerve (Sulcus nervi petrosi majoris) anterior to tegmen tympani. 4. Groove for lesser petrosal nerve (Sulcus nervi petrosi minoris) parallel and laterally to the groove for greater petrosal nerve.

Petrous part of the temporal bone Anterior surface

6. Trigeminal impression (Impressio trigeminalis) slight depression located medially marks the location of the sensory ganglion for the trigeminal nerve [V].

Petrous part of the temporal bone Anterior surface

6. Trigeminal impression (Impressio trigeminalis)

CAROTID CANAL 5. Carotid canal (Canalis caroticus) large circular opening posterolateral from the foramen lacerum along the petrous part of the temporal bone.

INTERNAL CAROTID ARTERY

1. Internal carotid artery 2. Vertebral artery 3. Cavernous sinus 4. Carotid canal 5. Anterior cerebral artery 6. Posterior cerebral artery

Petrous part of the temporal bone

Jugular foramen large opening between the occipital bone & petrous

vein draining the brain

3 of the 12 cranial nerves pass through here (CNs 9-10-11)

Styloid process needle-shaped bone marking

projects from the lower border of the temporal bone.

anteromedial to the mastoid process point of attachment for numerous muscles and ligaments

stylomastoid foramen

Transmits the nerve for the muscles of the

face

Posterior to the base of the styloid process

Between

styloid process & mastoid process

CN VII FACIAL NERVE

median portion body two great and two small wings extending outward from the sides of the body

two pterygoid processes project from it below.

SPHENOIDAL BONE OS SPHENOIDALE

at the base of the skull in front of the temporal bones 6 basilar part of occipital bone

.

SPHENOIDAL BONE OS SPHENOıDALE

sphenoidal crests

formed by the sharp posterior borders of the lesser wings

saddle-like bony formation on the upper surface of the body of the sphenoid

Anterior & posterior clinoid processes

Clinoid means «bedpost» 4 processes (2 anterior 2 posterior) surround hypophysial fossa “bed” of the pituitary gland like the posts of a four-poster bed.

composed of three parts

1. tuberculum sellae (horn of saddle) 2. hypophysial fossa (pituitary fossa) 3. dorsum sellae (back of saddle)

Superior orbital fissure between the greater and the lesser wings Foramen rotundum posterior to medial end of the superior orbital fissure Foramen ovale posterolateral to the foramen rotundum Foramen spinosum

posterolateral to the foramen ovale

on each side of the body,4 foramina perforate the greater wings of the sphenoid

Pterygoid processes lateral medial pterygoid plates Pterygoid fossa

Optical canal Chiasmatic sulcus

Major structures passing through spinal cord

meninges & spinal cord

vertebral arteries

anterior & posterior spinal arteries

spinal accessory nerve (CN XI)

OCCIPITAL BONE OS OCCIPITALE

at the back and lower part of the cranium

foramen magnum

cranial cavity communicates with the vertebral canal

4 parts of the occipital bone arranged around the foramen magnum

Squama

Basilar part

Lateral (condylar) portions

external occipital protuberance external occipital crest descends from the protuberance toward the foramen magnum.

superior nuchal line marks the superior limit of the neck.

extends laterally from each side of the protuberance.

occipital condyles

Two large protuberances @ lateral parts of the occipital bone Vertebral column-cranium articulation here

clivus (Lat., slope) shallow depression, incline behind the dorsum sellæ

cruciate eminence divides the interior surface into four fossae

cerebral fossae cerebellar fossae

internal occipital crest Lower divison of the

cross!

internal occipital protuberance

Centre of the cross!

hypoglossal canal for the hypoglossal nerve (CN XII) superior to the anterolateral margin of the foramen magnum

superior nuchal line marks the superior limit of the neck. extends laterally from each side of the protuberance. inferior nuchal line less distinct.

ETHMOID BONE Gk, ethmos, sieve sifter, eidos, form

Light, spongy, & cubical @ anterior part of the base of the cranium Between two orbits, at the roof of the nose Contributes to each of these cavities.

4 parts 1) A horizontal cribriform plate 2) Perpendicular plate 3) Two ethmoidal labyrinths

Crista galli midline ridge

Number 3

4 parts 1) A horizontal cribriform plate 2) Perpendicular plate 3) Two ethmoidal labyrinths

shallowest

Frontal bone

E

body and lesser wings of the sphenoid bone

greater wings of the sphenoid

squamous part of the temporal bone

petrous part of the temporal bone

X

largest and deepest

Occipital bone

X: dorsum sellae

SUTURAE

form of articulation

margins of bones united by a thin layer of fibrous tissue

LAMBDOID SUTURE Parietal bones

Occipital bones

CORONAL SUTURE Frontal bones

Parietal bones

SAGITTAL SUTURE Parietal bones

coronal & sagittal sutures intersect

sagittal & lambdoidal sutures

frontal, sphenoid, parietal & temporal bones

FONTANELLES

halves of frontal bone anteriorly

parietal bones posteriorly

@ the junction of sagittal, corona & frontal sutures

Bregma

1.5 y old. Closed.

parietal bones anteriorly

occipital bones posteriorly

@ the junction of lambdoid & sagittal sutures

Lambda

1 y old. Closed.

Sphenoidal & mastoid fontanelles fuse during infancy.

less important clinically than midline fontanelles

Bone marking @ which bone Important structures passing through

-particularly cranial nerves-

A lesion here might result in…

Carotid canal Temporal Internal carotid artery and nerve plexus Problem in the anterior arterial supply of the brain; as a result; weakness (hemiplegia) and numbness in the face, and extremities on the opposite side of the body, difficulty in speech, visual loss, etc.

Foramen magnum Occipital Continuation of brain and spinal cord; vertebral arteries and nerve plexuses; roots of accessory nerve [XI]; meninges

-

Foramen ovale Sphenoid Third branch of the CN V (Trigeminal nerve): Mandibular nerve [V3]

Sensorial loss in the mandibular region of the face

Foramen rotundum Sphenoid Second branch of the CN V (Trigeminal nerve): Maxillary nerve [V2]

Sensorial loss in the maxillary region of the face

Foramen spinosum Sphenoid - - Hypoglossal canal Occipital Hypoglossal nerve [XII] and vessels Loss of movement of the tongue. Internal acoustic meatus Temporal Facial nerve [VII]; vestibulocochlear nerve [VIII] Problems in hearing, balance, or

movements of the facial (expression) muscles

Jugular foramen Temporal Internal jugular vein; glossopharyngeal nerve [IX]; vagus nerve [X]; accessory nerve [XI]

-

Optic canal Sphenoid Optic nerve (II) Problems in vision. Stylomastoid foramen Temporal Facial nerve [VII] Loss of movement of the muscles of the

face

Superior orbital fissure Sphenoid Oculomotor nerve (III) Trochlear nerve (IV) Branches of ophthalmic nerve (II) Abducens nerve (VI)

Problems in vision.