1.1 Osteology and Arthrology of the Head Flashcards
Orbitomeatal plane
Inferior margin of orbit and superior margin of ext acoustic meatus in same horizontal plane
Parts of the cranium
- Neurocramium
- Viscerocranium
Neurocramium
- AKA cranial vault
- Bony base of the brain and meninges
What does the neurocranium contain?
Parts of cranial nerves and cranial vasculature
Parts of neurocranium
- Calvaria –> skullcap
- Cranial base –> floor (basicranium)
Bones of neurocranium
- Frontal
- Ethmoid
- Sphenoid
- Occipital
- Temporal (bilateral)
- Parietal (bilateral)
Viscerocranium
Facial skeleton
Bones of viscerocranium
Midline - Mandible - Ethmoid - Vomer Paired - Maxilla - Inferior nasal concha - Zygomatic - Palatine - Nasal - Lacrimal
What kind of joint is the temporomandibular joint?
Modified hinge synovial joint
Why is the TMJ considered a modified hinge joint?
Articular surfaces are covered by fibrocartilage instead of hyaline cartilage
What are the articulating surfaces of the TMJ?
- Head of mandible
- Articular tubercle of temporal bone
- Mandibular fossa
What does the articular disc do?
- Divides cavity into 2 separate synovial compartments
- Anterior and posterior bands make the disc biconcave
Describe the joint capsule of the TMJ
Loose
Where does the fibrous layer of the capsule of the TMJ attach?
- Margins of the articular area on temporal bone
- Around neck of mandible
What are the ligaments of the TMJ?
- Lateral ligament
- Stylomandibular ligament
- Sphenomandibular ligament
Which TMJ ligaments are instrinsic?
Lateral ligament (AKA temporomandibular l.)
Which TMJ ligaments are extrinsic?
- Stylomandibular ligament
- Sphenomandibular ligament
What does the lateral ligament do?
- Strengthen TMJ laterally
- Prevent posterior dislocation (along w/ postglenoid tubercle)
What is continuous with the lateral ligament?
The thick part of the TMJ joint capsule
What does the stylomandibular ligament do?
DOES NOT contribute significantly to strength of TMJ
Where does the sylomandibular ligament attach?
- Thickening of parotid gland
- Styloid process to angle of mandible
What does the sphenomandibular ligament do?
- Primary passive support
- “Swing rope” of mandible
Where does the sphenomandibular ligament attach?
Spine of sphenoid → lingula of mandible
Movements of the TMJ
- Elevation/Depression
- Protrusion/Retrusion
- Lateral movements
What muscles perform elevation?
Temporalis
Massester
Medial pterygoid
What muscles perform depression?
Lateral pterygoid
Suprahyoid
Infrahyoid
What muscles perform protrusion?
Lateral pterygoid
Masseter
Medial pterygoid
What muscles perform retrusion?
Temporalis
Masseter
What muscles perform lateral jaw movements?
Temporalis of same side
Pterygoids of opposite side
Masseter
Describe the arthrokinematics of the TMJ in the superior articular cavity
Depression- mandibular anterior translation
Protrusion- bilateral anterior translation
Describe the arthrokinematics of the TMJ in the inferior articular cavity
Depression- mandibular rotation
Describe the arthrokinematics of the TMJ during lateral deviation
Contralateral side: anteromedial translation
Ipsilateral side: Posterior translation and rotation
What are common fractures of the cranium?
- Depressed fractures
- Comminuted fractures
- Linear calvarial fractures
- Contrecoup (counterblow) fracture
- Basilar fracture
- Pterion fracture
Depressed fractures
- Fragment of bone is depressed inward
- Compresses/injures the brain
Comminuted fractures
Bone broken into several pieces
Linear calvarial fractures
- Most frequent type
- Occurs at point of impact
- Fracture lines radiate away in 2+ directions
Contrecoup (counterblow) fracture
Fracture occurs on the opposite side of cranium
Basilar fracture
- Involves bones forming base of skull
- CSF may leak into the nose and ear
- CN and blood vessel injury may occur
Pterion fracture
- Can be life-threatening
- Results from hard blow to side of the head
- Vessels may burst, putting pressure on cranium
What causes dislocation of the TMJ?
Excessive contraction of lateral pterygoids may cause mandible heads to dislocate anterior to the articular tubercles
What is the effect of a dislocation of the TMJ?
Cannot close the mouth
What causes arthritis of the TMJ?
Inflammation from degenerative arthritis
What is the effect of arthritis of the TMJ?
May result in dental occlusion and joint clicking (from delayed anterior disc movement)
