W8: Muscles Of Mastication Flashcards
What is the TMJ?
Temporomandibular joint = bilateral structure/joint. Two joints acting together to bring about movement. Articulation between the temporal bone and the mandible.
What happens to the TMJ in mastication?
In mastication, the TMJ is displaced during the act of chewing food. Displaces by alternate rhythmical movements in which jaw-opening and jaw-closing muscles are driven out-of phase with one another by a central motor pattern generator in the brainstem.
Where do all the muscles of mastication attach between?
The mandible
The skeleton of the cranium: sphenoid bone and temporal fossa of cranium
Jaw opening muscles/jaw depressors
Lateral pterygoid muscles - supplied by branch of the mandibular division of the trigeminal nerve
Weaker and not primary - digastric muscles assist
Action of the jaw opening muscles
Depress the mandible and to protrude the mandible
Primary jaw-close muscles/jaw elevators
Medial pterygoid muscles
Masseter
Temporalis
Actions of the jaw closing muscles
- elevate the mandible
- protrude the mandible (when acting bilaterally)
- retract the mandible
- move jaw from side to side (when acting unilaterally)
Motor supply of jaw closers
Motor branches of the mandibular nerve, a branch of the trigeminal nerve
What is Hilton’s law?
The nerves supplying the joint capsule also supply the muscles regulating the movement of the joint and skin over the joint.
When is the TMJ displaced?
Chewing food - mastication
Jaw-opening (e,g, during yawning)
Jaw-closing (e.g, taking a bite)
What is mastication?
The cyclical, rhythmical, motor act of chewing movements
Motor supply of the lateral pterygoid muscles
Lateral pterygoid nerve (a branch of CNV3)
Which muscles of mastication elevate the mandible?
All except lateral pterygoid
Which muscles of mastication protrude the mandible?
All except temporalis
