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CHAPTER 11
SKULL & CRANIAL BONES
SKULL
• Divided into 2 regions
1. Cranium
(8 bones)
2. Facial Bones
(14 bones)
2 Regions of Cranium
• Calvarium
1. Frontal
2. Right Parietal
3. Left Parietal
4. Occipital
• Floor
1. Ethmoid
2. Sphenoid
3. Right Temporal
4. Left Temporal
FRONTAL BONE
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Divided into 2 aspects:
- squamous (or vertical portion)
- orbital (or horizontal portion)
Landmarks associated with Frontal Bone
- Glabella
- Superciliary ridge (arch)
- Supraorbital margin (SOM)
- Supraorbital groove
- Frontal tuberosity (eminence)
Articulations
- Right Parietal Bone
- Left Parietal Bone
- Sphenoid
- Ethmoid
NOTE: The frontal bone articulates with 8 facial bones to be identified later.
Parietal Bones
• Right & Left Parietal
Bones
- make up the majority of
the lateral walls of the
cranium
• Articulations
- Frontal
- Occipital
- Temporal
- The opposite parietal
Occipital Bone
• Inferoposterior aspect of
calvarium
• Squamous portion
• External Occipital
protuberance (inion)
• Articulations
- R & L Parietals
- R & L Temporal
- Sphenoid
- Atlas (1st Cervical)
Temporal Bone
• Temporal Bones are paired
structures.
• R & L Temporal Bone
- Houses the organs of hearing
and balance
• Significant parts:
- zygomatic process
- temporomandibular fossa
- external acoustic meatus
(EAM)
-Mastoid process
- Temporal styloid process
Temporal Bone (continued)
• Consists of 3 main parts
1. squamous
2. mastoid
3. petrous portions
• Petrous ridge corresponds to
the level of the TEA
• Articulations
- parietal
- occipital
- sphenoid
- and two facials to be
discussed later
Sphenoid Bone
• Body
• Wings
• 4 major parts
1. lesser wing
2. greater wing
3. sella turcica
4. clivis
• Articulations
- all seven cranial bones
- and five facial bones
Sella Turcica
• Anterior Clinoid
Process
• Posterior Clinoid
Process
• Dorsum Sellae
• Best seen in a true
lateral.
Ethmoid Bone
• Crita galli
• Cribriform plate
• Lateral labyrinths
(masses)
• Perpendicular plate
• Superior and middle
nasal conchae
Cranial Sutures
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Lambdoidal
Squamosal
Coronal
Sagittal
Junction between sutures
Bregma
Lambda
Pterions
asterions
Joint Classification
Synarthroidal
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Infant Cranial Sutures
& fontanels
Anterior fontanel
R & L Sphenoid
fontanel
R & L mastoid
fontanel
Posterior fontanel
Skull Morphology
• 3 skull classifications
1. brachycephalic
2. mesocephalic (average-shaped)
3. dolicephalic
Cranial Topography
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Facial Landmarks
- Acanthion
- Glabella
- Gonion
- IOM
- Mental Point
- Midlateral orbital margin
- Nasion
- Outer and inner canthus
- SOG
- Supercilliary ridge (arch)
Body Planes
- MSP
- Interpubillary Line (IPL)
Landmarks of the Ear
- Auricle or pinna
- EAM
- TEA
-Tragus
•
Skull Positioning Lines
- AML (acantiomeatal line)
- EAM (external acoustic meatus)
- GAL (glabelloalveolar line)
- GML (glabellomeatal line)
- IOML (infraorbitomeatal line)
- LML (lips meatal line)
- MML (mentomeatal line)
- OML (orbitomeatal line)
•
No Abbreviations (students must spell out
each abbreviation to receive credit)
Positioning and Technical
Considerations
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Erect vs recumbent
Medium kVp 75-85
Small focal spot (if equipment allows)
AEC – center ionization cell
Short exposure time
Shielding
Skull Series
• Basic Projections
- AP axial (Towne)
- Lateral
- PA 0 degree
- PA 15 degree
(caldwell method)
• Special Projections
- PA axial (Haas)
- SMV
(submentovertex)
• Sella Turcica
- Lateral
- AP axial (Towne)