Cranium part 1

What is the average caliper measurements of the adult skull between the parietal eminences (lateral)

15 centimeters

What is the average caliper measurements of the adult skull from the frontal eminence to the external occipital protuberance?

19 centimeters

What is the average caliper measurements of the adult skull from the vertex to beneath the chin (SMV projection)

23 centimeters

What is the average mesocephalic skull?

width 75%-80% of length

What is a Brachycephalic Skull?

◦short, broad head

width is 80% greater than the length

What is a Dolichocephalic Skull?

◦long, narrow head

◦width is less than 75% of the length

How is the angle difference measured

between that petrous pyramids and the MSP

The mesocephalic skull forms what angle degree?

the petrous pyramids form a 47 degree angle

The Brachycephalic skull forms what angle degree?

has an angle greater than 47 degrees (approximately 54 degrees )

The Dolichocephalic skull forms what angle degree?

has an angle less than 47 degrees (approximately 40 degrees )

Superciliary Ridge (arch)

Ridge (arch) of bone that extends across the forehead above each eye

Supraorbital groove (SOG)

corresponds to the highest level of the facial bone mass, also the level of the floor of the anterior fossa of the cranial vault

Glabella

slightly raised triangular area between and slightly superior to the eyebrows and above the bridge of the nose

Nasion

junction of the two nasal bones and the frontal bone

Acanthion

midline point at the junction of the upper lip and the nasal septum, this is where the nose and the upper lip meet

Gonion or angle

lower posterior angle of each side of the jaw or mandible

Mental point

center of the mental protuberance

Interpupillary or interorbital line (IPL) is

◦a line that connects the pupils or outer canthi to the patient's eyes

When a patients head is placed in a true lateral position, IPL must be what to the plane of IR

exactly perpendicular

Top of ear attachment (TEA)

superior attachment of the auricle

Auricle (pinna)

External portion of the ear, large flap made up cartilage

Tragus

small cartilaginous flap that covers the opening of the ear

Canthi

junction of the upper and lower eyelids

Inner canthus

where the eyelids meet near the nose

Outer canthus

lateral junction of eyelid

SOM

superior rim of the bony orbit of the eye

Infraorbital margin (IOM)

inferior rim

Midlateral orbital margin

portion of the lateral rim that is near the outer canthus of the eye

EAM

opening of the external ear canal

Auricular point

center point of EAM

What is the most superior positioning line?

Glabellomeatal line (GML)

The dorsum sellae sits

posterior to the sella turcica making the back of the "saddle"

The GML refers to what

to the line between the glabella and the EAM

Orbitomeatal line (OML )

this area is located between the outer canthus (midlateral orbital margin) and EAM

Infraorbitomeatal line (IOML)

this area is formed by connecting the IOM to the EAM.

How much is the average difference between the angles of the OML and the IOML?

7 to 8 degrees

How much is the average difference between the angles of the OML and the GML?

7 to 8 degrees

Connecting the acanthion (AML) or the mental point (MML) to the EAM forms what?

forms the AML or MML

Lips-meatal line (LML)-

line from the junction of the lips to the EAM

what line is used for specific projections of the facial bones specifically the modified parietocanthial (modified Waters) projection

LML

Glabelloalveolar line (GAL)

connect the glabella to a point at the anterior aspect of the alveolar process of the maxilla.

What line is used for positioning a tangential projection for the nasal bones and the lateral position of the cranium

GAL

Inion

most prominent point of the external occipital protuberance.

What corresponds with the highest "nuchal" line of the occipital bone?

Inion

A straightedge can be used to what?

to illustrate that a cranial line is perpendicular

What is the preferred tool for skull positioning?

angle ruler

How many bones are in the cranium?

8

How many bones are in facial bones

14

Skull cap consist of what

>Frontal

>Right Parietal

>Left Parietal

>Occipital

The floor of the skull consist of what

>Right Temporal

>Left Temporal

>Sphenoid

>Ethmoid

What bone contributes to the formation of the forehead and the superior part of each orbit

Frontal bone

What are the main two parts of the frontal bone

> squamous or vertical portion, which form the forehead

> the orbital or horizontal portion, form the superior part of the orbit

SOG is the level of

level of the orbital plate or the highest level of the facial bone mass

Supraorbital notch (foramen)

small hole or opening within the SOM slightly medial to its midpoint. The supraorbital nerve and artery pass through this small opening

Frontal tuberosity (eminence)

a large, rounded prominence above the SOG

Orbital plate

Part of the frontal bone which forms most of the roof of the orbit

Below the orbital plate lies what?

facial bones

Above the orbital plate lies what?

is the anterior part of the floor of the brain case

Each orbital plate is separated from the other by what

the ethmoidal notch where the ethmoid bone sits

The frontal bones articulate with which four cranial bones?

> Right and Left parietals

> Sphenoid

> Ethmoid

The two parietal bones help to form

the lateral walls of the cranium and part of the roof

Parietal bones are

roughly square and have a concave internal surface

What is the widest portion of the entire skull

Parietal tubercles (eminences)

The frontal bone is primarily________ to the parietals with the occipital bone ________.

Anterior ; posterior

Parietal: articulates with which 5 bones?

> Frontal

> Occipital

> Temporal

>Sphenoid

> Opposite parietal

Inferoposterior portion of the calvarium (skull cap) is formed by what?

the single occipital bone

The squamous portion forms what?

most of the back of the head

What does foramen magnum mean?

Great hole aka a large opening at the base of the occipital bone through which the spinal cord passes as it leaves the brain

The two lateral condylar portions (occipital condyles) are

oval processes with convex surfaces, with one on each side of the foramen magnum

The two-part articulation between the skull and the cervical spine is called the

atlanto-occipital joint.

Occipital: articulates with which 6 bones?

> 2 Parietals

> 2 Temporals

> Sphenoid

> Atlas (first cervical vertebra)

The right and left temporal bones are complex structures that house what?

the delicate organs of the hearing and balance

Zygomatic process

extends anteriorly from the squamous portion of the temporal bone

The zygomatic process meets the temporal process of the zygomatic bone (facial bone) to form what

the easy palpated zygomatic arch

Each temporal bone is divided into how many primary parts?

3

The first part of the temporal part is

the thin upper portion that forms part of the skull wall, the squamous portion

What is the most vulnerable portion of the entire skull to fracture

squamous portion

The area posterior to the EAM is the

Mastoid portion

The Petrous portion is always called the what?

petrous pyramid

What does the peripheral nervous system consist of?

houses the organs of the hearing and equilibrium, including the mastoid air cells

What is the most thick and dense portion of the skull

Petrous portion

The petrous pyramids project anteriorly or posteriorly and toward the midline from the area of the EAM

anteriorly

Internal acoustic meatus serves to

transmit the nerves of the hearing and equilibrium

Temporal: articulates with which 3 cranial bones?

> Parietal

> Occipital

> Sphenoid

The sphenoid bone acts as what

the anchor for the other seven cranial bones

Sella turcia

Central depression on the body of the sphenoid, looks like a saddle from the side.

Where does sella turcica get its name from

Derives its name from words meaning "Turkish saddle"

What does the sella turcica do?

Partially surrounds and protects the pituitary gland

Clivus

This slightly depressed area forms a base of support for the pons (a portion of the brain stem) and for the basilar artery

Lesser wing

Extend laterally from the two anterior clinoid processes and body to the middle of each orbit on either side

Greater wings

Form a portion of the floor of the cranium and a portion of the sides of the cranium

Between the anterior body and the lesser wings on each side are

groove like canals through which the optic nerve and certain arteries pass into the orbital cavity

What view is the sphenoid bone best seen on

Oblique

Pterygoid Processes

Four processes that project downward from the inferior surface of the sphenoid body

Medial to these are the two medial pterygoid processes, which end inferiorly in a small hooklike processes

pterygoid hamuli.

The sella turcica and the dorsum sellae are demonstrated best on a _____ view?

lateral projection of the cranium

Sphenoid: articulates with which bones?

Because of its central location, the sphenoid articulates with all seven of the other cranial bones.

Cribriform plate

a smaller horizontal portion of bone and contains many foramina through which segmental branches of the olfactory nerves pass (looks perforated).

Crista galli

projects superiorly from the cribriform plate

Lateral Labyrinths help form what

the medial walls of the orbits and the lateral walls of the nasal cavity