Lecture 4: Midline bones Flashcards
What are the midline/UNpaired bones?
- Cranial bones: occiput and sphenoid
- Facial bones:
- mandible
- vomer
- ethmoid
- frontal
How do midline bones move?
Flexion and extension
- Rotate about a transverse axis, in an anterior-posterior direction.
How do paired bones move?
-
IR/ER
- Move about a AP axis, in a lateral motion (coronal plane)
When the unpaired bones flex, the paired bones => ____________.
- Unpaired bones = flex
- Paired bones = ER
FLEXTERNAL ROTATION
When the unpaired bones extend, the paired bones => _______
- Unpaired bones = extend
- Paired bones = Internally rotate
PArts of the ethmoid bone
- Cribiform plate + crista galli
- Perpendicular plate
- Lateral masses (2)
In SBS flexion: sphenoid tips ________ => ethmoid bone tips ______ on ____ axis
Other changes?
SBS flexion = ethmoid flexes
-
Sphenoid tips anteriorly => ethmoid bone (perpendicular plate) (flexes) on transverse axis
- => crista galli swings superior and posterior
- => lateral masses ER (down and out) bc attached to cribiform plate and use as hinge d/t pull of ER on maxilla = move as paired bones
In SBS extension: sphenoid tips ________ => ethmoid bone tips ______ on ____ axis
Other changes?
SBS extension = ethmoid extends
- Sphenoid tips posterior => ethmoid bone (perpendicular plate) (extends) on transverse axis in saggital plane.
- => crista galli swings inferior and anterior
- => lateral masses IR (down and out) bc attached to cribiform plate and use as hinge d/t pull of ER on maxilla = move as paired bones
- When sphenoid tips anteriorly (in flexion), the ethmoid tips ________
- When the ethmoid tips _______, the lateral masses of the ethmoid _______
- When the sphenoid tips posteriorly (in extension), the ethmoid tips ______
- When the ethmoid tips ______, the lateral masses of the ethmoid ______
- When sphenoid tips anteriorly (in flexion), the ethmoid tips posterior
- When the ethmoid tips posterior, the lateral masses of the ethmoid ER
- When the sphenoid tips posteriorly (in extension), the ethmoid tips anteriorly
- When the ethmoid tips anteriorly, the lateral masses of the ethmoid IR
Ethmoid mirrors what bone’s motion?
Occiput
Vomer same as what bone’s motion?
Sphenoid
What drives the vomer?
Sphenoid bone
When sphenoid moves into flexion => vomer moves into flexion.
What bones does the vomer articulate with?
- sphenoid
- ethmoid
- septal
- cartilage
- maxillae
- palantines
What is the function of the vomer with SBS flexion?
-
Depresses the hard palate with SBS flexion.
- In flexion => creates a wider flat palate
- In extension => creates a narrower flat palate
- Posterior part: depresses the palatines, flattening the roof of the mouth
- Anterior part: ascends to allow premaxillae to ER.
When the SBS is in flexion,
the ethmoid will move in the same direction as the _____.
vomer will move in the same direction as the ____.
SBS flexion
- ethmoid = occiput
- vomer = sphenoid
vowels move together (e = o) = consenent move together (v = s)
What causes SD to the vomer?
SD to the vomer is usually due to the position of the sphenoid, caused by trauma to the face
How do you palpate the CRI?
Vault contact
- Index fingers rest on the greater sphenoid wings
- Middle fingers are usually anterior to the ear
- Ring fingers rest on the mastoid process
- Pinky fingers rest or reaches back to the occiput
- Palms may very lightly rest upon the parietals
- Thumbs may gently contact the frontal, hover above or rest contacting your own 2nd MCP
SD of SBS
- 1. Lateral strain
- 2. Vertical strain
- 3. Torsion
- 4. SB rotation
- 5. Compression
Lateral strain of SBS
Lateral strain – named for the direction the base of the sphenoid is moving in
- Occurs when sphenoid and occiput rotate L/R in the same direction about 2 superior/inferior (vertical) axes that go through the base of the sphenoid and occiput, producing a shearing motion at the SBS.
-
The lateral strain is named for the motion of the base of the sphenoid (basisphenoid): thus, if it tips to the L => R lateral strain
- Right lateral strain – the sphenoid and occiput turn, anteriorly facing the left
- Left lateral strain – the sphenoid and occiput turn, anteriorly facing the left
- Injury anterior or posterior to SBS to cause the lateral motion
Palpatory findings with lateral strain
- 1st fingers move in opposite direction from pinky fingers
- Side of strain moves anteriorly
Vertical strain SD
Vertical strain – named for the direction of the base of the sphenoid
Occurs when sphenoid and occiput rotate in the same direction about 2 left/right (transverse) axes.
- The transverse axis for the sphenoid ==> goes through the zygomatic process of the temporal bone and body of the sphenoid.
- For the occiput, the axis is midway between the mastoid process and asterion, above the foramen magnum.
Strain is described for the superior/inferior shift of the sphenoid in relation to the occiput.
- Inferior vertical strain – the sphenoid and occiput rotate posteriorly around axis
- Superior vertical strain – the sphenoid and occiput rotate anteriorly around axis
What palpatory findings do we see for a vertical strain?
SD due to: Injury superior/inferior in front of or behind the SBS
- Superior strain: “First fingers move away from doctor, and pinky fingers move to doctor”
- Inferior strain: “First fingers move TO doctor, and pinky fingers move AWAY from doctor”
SBS Torsion
Torsions are named “L/R torsion” depending on the greater wing of the sphenoid that is higher.
Sphenoid and occiput will rotate in opposite directions around a anterior-posterior axis (saggital), creating a twist at the SBS
- L torsion => sphenoid moves superior on L; occicput inferiorly on L
- R torsion => sphenoid move superior on R; occiput moves inferior on R
SBS torsion palpatory findings and cause
Injury: hit w a roll in jaw or side of occiput
Palpatory findings: 1st finger and pinky of 1 hand move superior; while other hand moves inferior
