RAD 233 Skull

How many bones in the skull

22

the bones in the skull are divided into two group which are what and how many bones in each group?

Cranial- 8

Facial- 14

The Cranial bones further subdivided into

Calvaria

Floor

Which bones make up the Calvaria bones of the cranium

Frontal

Occipital

Right and Left Parietal

4 bones total

Which bones make up the Floor bones of the cranium

Ethmoid

Sphenoid

Right and Left Temporal

4 bones total

inner layer of spongy bone separating two outer plates of compact tissue (composition of calvarium bones)

Diploe

What’s the outer plate of the of compact tissue in the skull

Pericranium

What’s the inner plate of compact tissue in the skull

Endocranium

fibrous joints that connect the bones of the skull

Sutures

between frontal and parietal bones

Coronal suture

on top of head between two parietal bones

Sagittal

between temporal bone and parietal bones

Squamosal (lateral suture)

between occipital and parietal bones

Lambdoidal

junction of coronal and sagittal sutures

Bregma (anterior fontanelle)

junction of sagittal and lambdoidal sutures

Lambda (posterior fontanelle)

areas of incomplete ossification in infant skulls (soft spots)

Fontanels

Adult cranial size usually achieved by what age

12

how many regions is the cranial floor divided internally?

3

houses frontal lobes of cerebrum

Anterior cranial fossa

Where does the Anterior cranial fossa extend to?

extends from anterior frontal bone to lesser wings of sphenoid

houses temporal lobes

Middle cranial fossa

Where does the middle cranial fossa extend to?

extends from lesser wings of sphenoid to apices of petrous ridges

deep depression posterior to petrous ridges

Posterior Cranial fossa

What does the posterior cranial fossa protect

cerebellum, pons, and medulla oblongata

Which skull morphology has the petrous pyramids project anteriorly and medially at 47-degree angle from MSP

Mesocephalic

Which skull morphology has the petrous pyramids project anteriorly and medially at 54-degree angle from MSP

Brachycephalic skull

Which skull morphology is short from front to back, broad from side to side, and shallow from vertex to base

Brachycephalic skull

Which skull morphology has the petrous pyramids project anteriorly and medially at 40-degree angle from MSP

Dolichocephalic skull

Which skull morphology is long from front to back, narrow from side to side, and deep from vertex to base

Dolichocephalic skull

Which skull morphology is a typical skull

Mesocephalic

Has vertical portion (frontal squama) and horizontal portions

Frontal Bone

Forms forehead and anterior part of cranial vault

Frontal Squama (vertical portion)

Forms orbital plates, part of roof of nasal cavity, and greater part of anterior cranial fossa

Horizontal portion of the frontal bone

What are the landmarks found in the Frontal Bone

Frontal eminences

Supraorbital Margins

Supraciliary arches

Supraorbital foramina

Glabella

2 rounded elevation in the frontal bone

Frontal eminence

Below the frontal eminence

Superciliary arches

Smooth elevations between the superciliary arches

Glabella

Allows nerves and blood vessels to pass

Supraorbital foramen

Contained between the two tables of squama on each side of MSP, separated by a bony septum

Frontal Sinuses

The frontal bone articulates with

Partial- coronal suture

Sphenoid-frontosphenoidal suture

Nasal-frontonasal suture

And ethmoid

Posterior to the nasal bone

Ethmoid bone

What does the Ethmoid bone consist of ?

Horizontal plane

Vertical Plane

Labyrinths

Two light, spongy masses in the Ethmoid bone

labyrinths

Where is the ethmoid bone located

between the orbits

The ethmoid bone forms part of what ?

anterior cranial fossa

nasal cavity

orbital walls

bony nasal septum

What is the horizontal part of the ethmoid bone called

Cribriform plate

Cribriform plate contains numerous foramina for that serve what purpose?

Transmission of olfactory nerves

conical projection at anterior midline of cribriform plate

Crista galli

vertical portion; forms superior portion of bony nasal septum in the ethmoid

Perpendicular plate

Contain ethmoid sinuses or air cells

Labyrinths

Air cells of the labryrinth are divide into what groups

Anterior, middle, and posterior

The walls of the labyrinth form part of what

medial walls of orbits and lateral walls of nasal cavity

the labyrinths have two thin, scroll-shaped projections

superior and middle nasal conchae

What does the Ethmoid bone articulate with

frontal

sphenoid

lacrimal

maxilla

vomer

Square in shape and form large part of side of cranium and back portion of cranial roof

Parietal bone

Which surface of the parietal bone is convex and which is concave?

External- convex

Internal- concave

prominent bulge near center of external surface of each bone

Parietal eminence

This is the point where the width of the skull should be measured to set technique

Parietal eminence

What does the parietal bone articulate with

each other at the sagittal suture

frontal

temporal

occipital

sphenoid

How many bones does the Parietal bone articulate w/ ?

5

What bone does the parietal bone articulate with posteriorly and which bone does it articulate with anteriorly

posteriorly- occipital

anteriorly- frontal

Irregular, wedge-shaped bone that vaguely resembles a bat

Sphenoid bone

Where is the sphenoid bone located

base of cranium anterior to temporal bones and basilar portion of occipital

What does the sphenoid bone consist of

body

2 lesser wings

2 greater wings

2 pterygoid processes

Contains two sphenoid sinuses and forms posterior bony wall of nasal cavity

Body of sphenoid

deep depression on superior surface of body of sphenoid

Sella turcica

The sella turcica houses what

pituitary gland

where is the pituitary gland located at

MSP of cranium ¾ inch (1.9 cm) anterior and superior EAM

anterior border of sella

Tuberculum sellae

posterior border of sella

Dorsum sellae

top borders of dorsum

Posterior clinoid processes

slanted area of bone posterior and inferior to dorsum (Continuous with basilar area of occipital) supports pons

Clivus

Optic groove extends across anterior portion of tuberculum sellae where does it end

each side at the optic canal

opening into the apex of orbit for transmission of optic nerve and ophthalmic artery between the roots of the anterior clinoid process

optic foramen

Arise from anterior and superior portion of the sphenoid body and lie horizontally on each side

lesser wings

the lesser wings form part of what

posteromedial portion of orbital roofs

posterior portion of anterior cranial fossa

upper margin of superior orbital fissure

optic canals

the middles ends of the lesser wings form what

anterior clinoid processes

The 2 roots of the Anterior clinoid processes

Anterior(thin)

Posterior(thick) -sphenoid strut

arise from sides of body and curve laterally, posteriorly, anteriorly, and superiorly

Greater wing

the greater wings form what

form part of middle cranial fossa

posterolateral walls of orbit

what are the 3 foramina situated on the greater wing of the sphenoid

rotundum

ovale

spinosum

arise from lateral portions of inferior surface of body and medial
portions of inferior surfaces of greater wings

Pterygoid processes

The Pterygoids articulate with

palatine bones anteriorly

vomer as part of nasal cavity

Process in the Medial plate of the pterygoids that make it longer than the lateral pate

Pterygoids hamulus

The sphenoid articulates with what

All 7 bones

Forms posterior half of cranial base and greater portion of posterior cranial fossa

Occipital bone

where is the occipital bone situated

posteroinferior

what 4 parts make the occipital bone

squama

2 occipital condyles

basilar portion

large opening through which medulla oblongata passes as it exits cranium

Foramen magnum

Curves posteriorly and superiorly from foramen magnum convex outside

Squama

prominent process on squama

External occipital protuberance (Inion)

the external occipital protuberance also corresponds to

internal occipital protuberance

project anteriorly from each side of squama only bony JT between skull and neck

occipital condyles

Anterior to condyles and transmits hypoglossal nerves

Hypoglossal canal

Posterior to condyles transmit emissary veins

Condylar canals

Drains blood via internal jugular vein and transmit 3 cranial nerves

Jugular foramen

the occipital condyles fuse with the basilar portion to complete what?

foramen magnum

Anteriorly and superiorly fuses w/ body of sphenoid to form Clivus (anterior inferior)

Basilar portion

what does the occipital bone articulate with

two parietals- lambdoidal sutures

the two temporals- occipitomastoid sutures

the sphenoid

the atlas (C1)- occipitoatlantal JT

Form large part of middle cranial fossa and a small part of posterior cranial fossa and are the ear bones between greater wings of sphenoid and occipital bone

Temporal bones