Skull Flashcards
How many cranial bones
8
Cranial bones are divided into which 2 groups?
Calavaria and Floor
Bones of the cranial vault are composed of
Two plates of compact tissue separated by an inner layer of spongy tissue (diploe)
Bones of the cranium are formed by
Sutures
What are the sutures
Coronal, Sagittal, Squamosal, and Lambdoidal
Coronal Suture
Found between frontal and parietal bones
Sagittal Suture
Found at the top of the head between the two parietal bones
Junction of the coronal and sagittal sutures
Bregma
Squamosal Suture
Found between the temporal and parietal bones
Lambdoidal Suture
Found between the occipital and parietal bones
Lambda
Junction of the lambdoidal and sagittal sutures
Pterion
Junction of the parietal bone, Squamosal Suture, and greater wing of the sphenoid found on the lateral aspect of the skull
Asterion
Junction of the occipital bone, parietal bone, and mastoid portion of the temporal bone
Cranial floor is divided into three regions:
Anterior, middle, and posterior cranial fossae
The anterior cranial fossa extends from
The anterior frontal bone to the leader wings of the sphenoid
The middle cranial fossa accommodates
The temporal lobes and extends from the lesser wings of the sphenoid bone to the apices of petrous portions of the temporal bones
The superior surface of the sphenoid bone presents
Deep depressions called the sella turcica, which contains the pituitary gland
Mesocephalic
Average skull shape
Bradycephalic Skull
Shorter and wider skull
Doliochocephalic Skull
Long and narrow skull
Lateral Position
- Side of interest closest to the IR
- MSP parallel to the plane of the IR
- IOML perpendicular to the front edge of the IR but parallel with the long axis
- Interpupillary line perpendicular to IR
Where does the CR enter in a lateral?
Perpendicular, 2 inches above EAM.
What does a lateral image show?
Superimposed halves of the cranium. The sella turcica (in profile), anterior clinoid processes, dorsum sellae, and posterior clinoid processes.
How do you tell there’s no tilt or rotation in a lateral?
Superimposed orbital roofs and greater wings of the sphenoid, superimposed mastoids, EAM, and TMJ
PA Projection
- OML perpendicular to the IR
- MSP perpendicular
Where does the CR enter for a PA?
Perpendicularly, directed to exit the nasion
Where does the CR enter for Caldwell Method
Same as PA. Directed to exit nasion at an angle of 15 degrees caudad.
To show the superior orbital fissures, what do you do with the CR in a PA?
Direct the CR through the midorbits at an angle of 20-25 degrees caudad.
Where are the petrous portions in a PA projection with a perpendicular central ray?
Inside the orbits
Where are the petrous portions in the Caldwell method?
Into the lower one third of the orbits
What structures are seen on a PA?
Posterior ethmoidal air cells, crista galli, frontal bone, and frontal sinuses. Caldwell shows anterior ethmoidal air cells as well.
AP Projection/AP Axial
- MSP and OML perpendicular to the IR
- CR perpendicular or directed at the nasion at an angle of 15 degrees cephalad.
- Orbits are considerably magnified
Towne Method (AP Axial)
- MSP and OML perpendicular to IR
- IR’s upper margin at top of vertexg
Townes CR (AP Axial)
- Perpendicular to the foramen magnum at a caudal angle of 30 degrees to the OML or 37 to the IOML
- Enters approximately 2 and a half inches above the glabella and passes through EAM
AP Axial structures
Image of the petrous pyramids, the posterior portion of the foramen magnum, dorsum sellae and the posterior clinoid process projected within the foramen magnum
PA Axial (Haas)
- Used for demostrating sellar structures projected within foramen magnum on patients who cannot be adjusted accordingly for Townes (AP axial)
- MSP and OML perpendicular to IR
Haas CR
Directed at a cephalad angle of 25 degrees to the OML to enter 1 1/2 inches below the inion and exits 1 1/2 inches above the nasion
Haas Structures
Shows the occipital region of the cranium and symmetrical petrous pyramids and the dorsum sellae and posterior clinoid processes within the foramen magnum
