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give the total number of cranial bones and their names:
- 8 cranial bones:
- frontal bone
- parietal bones (2)
- temporal bones (2)
- occipital bone
- ethmoid bone
- sphenoid bone
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how many bones of the entire skull are there?
- 8 cranial bones
- 14 facial bones (next unit)
- 22 bones of the skull in total
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give the correct term for the "skull cap" and the bones it is comprised of:
- the Calvarium:
- frontal bone
- 2 parietal bones
- occipital bone
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what is the name for the widest point of the skull?
parietal eminence
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while the inferior nasal conchae is a separate facial bone, the superior and medial nasal conchae are actually a part of which cranial bone?
ethmoid bone
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What two bones make up the bony nasal septum?
- the upper part is the perpendicular plate of the ethmoid bone
- the lower part is the vomer
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the brain and spinal cord are covered by three layers of _______ that adhere to the cranium by way of the _____________.
- meninges
- meningeal grooves
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on the interior surface of the cranium, the large grooves are the ___________ and the small grooves are the ___________.
- sulci/sulcus
- meningeal grooves
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the joints of the cranium are of the ____________ type.
fibrous/synarthrodial
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give the approximate ages at which each skull fontanel closes:
- posterior: 1 month
- anterior: 2 years
- sphenoids: 3 months
- mastoids: 2 years
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describe the growth rate of the average cranium:
- grows rapidly until about 5-6 years of age
- then grows slowly until around 12 years
- (mostly reached its full size at that point)
-
irregular bones that sometimes form along the fontanels when they are closing:
worman/sutural bones
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give the dimensions of the labeled spans and three aspects to remember when considering these dimensions:
- A. 6 inches (15cm)
- B. 7 inches (18cm)
- C. 9 inches (22cm) - submentovertical aspect
- there is less atrophy in the skull than anywhere else in the body
- the skull is wider in the back than in the front (parietal area is widest point)
- internal structures are located in a different place if these measurements are off by more than an inch.
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describe the petrous pyramids (4):
- part of the temporal bone
- densest part of cranium
- houses all internal ear structures
- used to measure pt's head to determine shape category
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name the three common shapes of the skull:
- mesocephalic skull (average)
- brachycephalic skull (wider than average)
- dolichocephalic skull (narrower than average)
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give some specifics about the mesocephalic skull:
- the most average
- petrous pyramids open to the back at a 47° angle to MSP
- add or subtract 7° to this angle for the other two skull shapes!!
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give some specifics about the brachycephalic skull:
- the wider than average skull
- it is wider than it is from front to back
- it is shallow from vertex to base
- petrous pyramids open to the back at a 54° angle to MSP
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give some specifics about the dolichocephalic skull:
- the more narrow than average skull
- long from front to back
- deep from vertex to base
- narrow from side to side
- internal structures are lower in reference to IOML
- petrous pyramids open to the back at a 40° angle to MSP
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what represents the highest level of facial bone mass?
the supraorbital groove (SOG)
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give a definition and several aspects of the frontal sinus:
- an air-filled cavity of the frontal bone located between the inner and outer table of the skull
- has one main septum, the inner sinus septum
- varies in shape and size in individuals
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what bones does the frontal bone articulate with?
- parietal bones
- greater wing of sphenoid
- nasal bones
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name three structures that the ethmoid bone helps to form:
- helps form part of the anterior cranial fossa (where the brain sits)
- helps form orbital cavity (ethmoid sinus directly between eyes)
- helps form nasal cavity (perpendicular plate)
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what is the function of the foramina on top of the cribiform plate?
for passage of the olfactory nerves
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crista galli is the attachment site for the:
- falx cerebri (the duramatter of the brain)
- (the membrane that divides cerebrum into right and left halves)
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the posterior part of the sphenoid and basilar portion of the occipital:
clivus
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the portion of the occipital bone that is anterior to the foramen magnum is the:
basilar portion
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the jugular foramen is formed between which two bones?
- temporal bone
- occipital bone
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the portion of the occipital bone that includes everything superior to the foramen magnum:
squamous portion
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what do the condyles of the occipital bone and C1 form?
the occipito-atlantal joint
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name the three main parts of the occipital bone:
- squamous portion
- basilar portion
- condyles
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what part of the sphenoid does the temporal bone articulate with?
greater wing
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which part of the cranial fossa does the temporal bone help to form?
- mainly the middle cranial fossa
- slightly with posterior cranial fossa
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the zygomatic process of the temporal bone articulates with the ___________ (facial bone) to form the ____________.
-
a long, slender, pointed process that projects posteriorly to the mandible and anteriorly to the EAM:
styloid process
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the thickest, densest bone in the skull, used as an identifying landmark in radiographs for positioning of the skull:
petrous portion of temporal bone
-
zygomatic process is continuous with a ridge of bone called the:
temporal line
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______________ fits into the mandibular fossa of the temporal bone.
- condyle of mandible
- (forms the temporomandibular joint - TMJ)
-
the __________________ prevents the mandibular condyle from slipping too far forward from the mandibular fossa of the temporal bone.
articular tubercle
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the portion of the temporal bone that helps to form the EAM:
tympanic portion
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describe how the petrous portion of the temporal bone projects for different skull shapes:
- projects posteriorly 47° to mastoid and squamous portions in normal skull (mesocephalic)
- projects posteriorly 40° to mastoid and squamous portions in narrow skull (dolichocephalic)
- projects postiorly 54° to mastoid and squamous portions in wide skull (brachycephalic)
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separates internal ear from the brain:
tegman tympani
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the first and largest air cell to develp in the mastoid:
mastoid antrum
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a part of the middle ear that is covered by the tegman tympani:
tympanic cavity
-
where is the base of the temporal bone located?
- where the petrous portion joins with the squamous and mastoid portions
- (apex is tip of petrous portion)
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the top of the temporal bone that is located externally at the TEA (top of ear attachment):
petrous ridge
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what are the bones of the cranium joined by?
sutures
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how many areas of incomplete ossification are in newborns?
- six:
- anterior
- posterior
- sphenoidal (2)
- mastoid (2)
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what two parts is the skull divided into?
-
name the two functions of the skull:
- protects the brain
- supports the face
-
what are the two plates of compact tissue separated by?
diploe
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which plate of the skull is thicker?
the outer layer
-
how many regions is the cranial floor divided into?
- three:
- anterior
- middle
- posterior
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name the major sutures of the skull:
- coronal: between frontal and parietals
- sagittal: between two parietals
- squamosal: between temporal and parietal
- lambdoidal: between occipital and parietals
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name the sutural points:
- bregma: junctions of coronal and sagittal sutures
- lambda: juntion of lambdoidal and sagittal sutures
- pterion: junction of parietal, squamosal suture and sphenoid
- asterion: junction of occipital, parietal, mastoid portion of temporal
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name the two main parts of the frontal bone:
- vertical (squamous) portion
- horizontal (orbital plates) portion
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what are the orbital plates separated by?
ethmoid notch
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what is located between the inner and outer table of the frontal bone?
frontal sinus
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what fits into the ethmoid notch?
- crista galli
- cribiform plate
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describe the position of the ethmoid bone:
between the orbits
-
what are the two lateral masses of the ethmoid that hold aircells called?
labyrinths
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what are the three main parts of the ethmoid?
- lateral masses
- vertical plate
- horizontal plate
-
what makes up the horizontal plate of the ethmoid?
the cribiform plate
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what makes up the vertical plate of the ethmoid?
the perpendicular plate
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what does the perpendicular plate articulate with?
the vomer
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how do the nasal conchae project and what do they divide?
- inferior from labyrinths
- divide nasal cavity
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name the three nasal conchae and an alternate name for them:
- nasal turbinates
- superior, middle, and inferior
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describe the classifications of the nasal conchae:
- the superior and middle conchae are part of the ethmoid bone
- the inferior concha is a separate facial bone
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what the name of the area that is the widest measurement of the skull?
parietal eminence
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what bone is anterior to the temporal bones and anterior to the basilar portion of the occipital bone?
sphenoid bone
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what contains the pituitary gland?
sella turcica
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what does the sphenoid articulate with?
all other seven cranial bones
-
give another name for the sella turcica:
hypophyseal fossa
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where on the sphenoid bone are the sphenoid sinuses located?
the body
-
where is the pons of the brain situated within the cranium?
at the clivus
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where do the optic nerves cross and pass through the optic canal?
optic chasm/groove
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list the three foramen of the sphenoid bone from anterior to posterior:
- foramen rotundum
- foramen ovale (largest)
- foramen spinosum (smallest)
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allows blood to drain from the brain:
- jugular foramen
- (via jugular veins)
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list the five portions of the temporal bone:
- squamous
- zygomatic
- tympanic
- mastoid
- petrous
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what is formed by the articulations of the condyle of the mandible and the mandibular fossa of the temporal bone?
tmj (tempomandibular joint)
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what keeps the condyle of the mandible from slipping out of the fossa where it articulates with the temporal bone?
articular tubercle
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what is noticable about the mastoid tip when comparing genders?
the tip is generally larger in males
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what is the external landmark used to locate the petrous ridge?
the TEA (top of ear attachment)
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name the structures located in the middle ear:
- ear drum
- ossicles
- tympanic cavity
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name the structures located in the internal ear:
- cochlea vestibule
- semicircular canals
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for the lateral skull projection, what should be done for a hypersthenic patient?
place support under the head
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for the lateral skull projection, what should be done for a hyposthenic or asthenic patient?
place support under thorax/chest
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for the AP skull projection, a support may be needed under the head for what body habitus?
-
if you want to view the sella turcica, where would you center?
- lateral projection centered to 3/4" anterior and 3/4" superior to EAM
- (with the IOML aligned)
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what is demonstrated on a dorsal decubitus projection of the skull?
sphenoid effusion (a major indicator of fracture at base of skull)
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where are the petrous pyramids located in a PA projection of the skull vs. a PA axial projection?
- PA: in the orbits
- PA axial: in bottom 1/3 of orbits
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what is the name of the projection used to view the occipital bone?
- townes/grashey method
- haas method
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what is seen in the foramen magnum in the townes projection?
- the posterior clinoid processes
- dorsum sellae
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describe the positioning for the Haas Method?
- 25degrees cephalic (PA)
- centered to 1.5" below inion
- CR exits 1.5" superior to nasion
- also called reverse townes
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what bone is of primary interest for the townes and haas methods?
occipital bone
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what are the three other names for the submentovertical projection of the skull?
- SMV
- schuller method
- basal projection
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what do the pterygoid processes help to form?
nasal cavity
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what is located between the zygoma and the greater wing of the sphenoid?
inferior orbital fissure
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what is located between the greater and lesser wings of the sphenoid?
superior orbital fissure
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how many sphenoid sinuses are there?
two
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where the eustacian tube connects the middle ear to the nasopharynx:
- tympanic cavity
- (helps to equalize pressure)
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what projection(s) best demonstrate the crista galli?
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describe and name the reverse SMV projection:
- chin down on table/IR surface
- shoot down through vertex
- called the VSM
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what projection best demonstrates the foramen rotundum?
waters
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what projection best demonstrates the foramen spinosum and ovale?
SMV
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what projection best demonstrates the optic foramen?
orbits
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what projection best demonstrates a sphenoidal effusion?
- upright lateral
- dorsal decubitus
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what is seen on the lateral projection of the skull?
every bone of the skull
-
what projection best demonstrates the frontal bone?
PA/AP
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in which projection do the orbits appear enlarged?
AP (they're further away)
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what projection best demonstrates the base of the skull?
SMV
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what do you do if the pt cannot duck the chin enough to use the OML for the townes method?
use the IOML with a 37° angle (increased angle by 7°)
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name two projections that will cause the petrous pyramids to appear above the orbits:
- AP with caudal angle
- PA with cephalic angle
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what projection best demonstrates the posterior ethmoid?
PA
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what projection best demonstrates the anterior ethmoid?
PA axial (Caldwell)
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an opening into the apex of the petrous portion is for the:
- carotid canal
- (runs alongside the body of the sphenoid bone)
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