TMJ Anatomy Flashcards
Components of TMJ
- Temporal bone
- Mandible
- Articular Disc
- 2 distinct synovial chambers (upper/lower)
Upper Synovial Chamber
-of the articular disc and glenoid fossa
Lower Synovial Chamber
-of the articular disc and mandibular condyle
Glenoid Fossa
-fossa in temporal bone where mandibular condyle rests
Parts of Temporal Bone
(Posterior to anterior)
- posterior glenoid spine,
- glenoid fossa
- articular eminence
- articular tubercle
Articular Eminence
- load bearing region for the mandible on the temporal bone
- convex
Articular Tubercle
- most anterior aspect of temporal bone of joint
- does not provide a bony stop to translation of mandibular condyle
Mandibular Condyles
-typically oriented with medial pole of condyle more posterior to lateral aspect and projects medially 15-20mm from ramus
Ramus
- Vertical component of mandible
- has 2 projections (coronoid process and mandibular condyle)
- Sandwiched by Mm (Masseter and medial pterygoid)
Coronoid process
- Anterior projection of ramus
- Attachment sight for temporalis and masseter Mm
Articular Disc
- Biconcave
- Improve congruency between 2 convex surfaces
- Vascularized and innervated at each end (not in middle)
- Central segment load bearing portion
Articular Disc Attachments
Restrict posterior migration of disc:
- Condyles
- Joint capsule (anteriorly)
- Superior/middle heads of lateral pterygoid
Restrict Anterior migration:
-Bilaminar Retrodiscal Pad (superior band: returns disc to neutral; Inferior band: checks anterior translation of disc)
Mandibular Movements
- Depression
- Elevation
- Lateral deviation
- Protrusion
- Retrusion
Normal Depression ROM
40-50mm
Normal Lateral Deviation ROM
8-10mm
Normal Protrusion ROM
5-6mm (on slides)
6-9mm (on notes doc)
Normal Retrusion ROM
2-3mm
no more than 3mm
1st Phase of depression
- Condules rotate anteriorly under the disc
- Mandible depresses 11-25mm
2nd Phase of depression
- condyle/disc complex translates anteriorly and inferiorly on articular eminence
- accounts for remainder of opening to 40-50mm
Lateral deviation Mechanics
(to right)
- Right condyle rotates R on vertical axis
- Left condyle translates anteroinferiorly on articular eminence
Protrusion Mechanics
- Forward translation of condyles
- no rotation
- only in upper joint of TMJ
Retrusion Mechanics
-Limited by soft tissue approximation of retrodiscal pad between condyle and posterior glenoid spine as well as TM ligament
Chewing
complex combo of elevation, lateral deviation, and protrusion of mandible
Muscles of TMJ
- Temporalis
- Masseter
- Medial Pterygoid
- Lateral Pterygoid
- Suprahyoids
- Infrahyoids
9 Points of Hypermobility test
1/2: pinky extends >90* 3/4: Thumb to forearm 5/6: hyperextension of elbows >10* 7/8: hyperextension of knees 9: palms flat on floor with knees straight
Muscles of Elevation
- Masseter
- Temporalis
- Pterygoids
Muscles of Protrusion
- Masseters
- Pterygoids
Muscles of Depression
- Eccentric contraction of elevation muscles
- Depression against resistance: digastric muscle (concentric)
- Other depressors: lat pterygoid and gravity)
Muscles of Retrusion
Temporalis
Ligaments
- Temporomandibular Ligament
- Stylomandibular Ligament
- Sphenomandibular Ligament
Temporomandibular Ligament
- Attach from articular eminence to neck of condyle
- Limits lateral, inferior & posterior movement of mandible
- Suspends mandible against gravity
Stylomandibular Ligament
- Styloid process to mandibular angle
- appear to be suspensory ligaments
Sphenomandibular Ligament
- Sphenoid to mandibular angle
- appear to be suspensatory ligaments
Inferior Joint capsule
- joins the disc to the nect of the condyle
- tighter than superior capsule
Superior Joint capsule
- Loosely joins the disc to the temporal bone
- Allows for translation of disc on articular eminence
CN V
- Trigeminal N
- Mm of mastication
- Sensory to face, scalp, teeth, oral cavity
Auriculotemporal Nerve
- branch of CN V
- innervation of TMJ and some ear symptoms associated with TMJ
CN VII
- Facial N
- Mm of facial expression
- Digastric Mm
Unilateral Action of Pterygoids
Deviate to opposite side
Unilateral Action of Temporalis
Deviate to same side
Active Control of Disc
- Lat pterygoid oriented anteromedially in relationship to condyle and attaches to anterior disc
- Ptery silent in opening but active in closing
- thought to control eccentric return of disc to neutral position