TMJ

Question 1

What are the landmarks of the mandible?

Answer 1

-mental protuberance: “chin”

-mental foramen: hole where V3 of CN5 exits

-body: flat part of jaw

-angle: where the jaw turns

-ramus: the flat part of the jaw after the angle turns upward

-coronoid process: flat extension of bone (anterior)

-condylar process: round process of bone (posterior)

Question 2

What are the structures of the TMJ?

Answer 2

-condylar process of mandible: rounded end of mandible

-articular disc: runs between mandibular fossa and condyle

-mandibular fossa of temporal bone: concave arch that forms space for the condylar process to sit in

-articular tubercle of temporal bone: bump that sits just anterior to the mandibular fossa on the temporal bone

-joint capsule

Question 3

What TMJ movements open the mouth?

Answer 3

Rotation: initial movement (joint spins around axis and rotates), opens mouth about 1 finger width

Translation: moth opens wide, jaw has to move/slide forward over the articular tubercle

Question 4

What are the muscles of the TMJ?

Answer 4

Close mouth:
-temporalis: sits in the temporal fossa and anchors to choroid process

-masseter: anchors to mandible

-medial pterygoid: more interior, comes off of process of sphenoid bone and anchors to mandible

> involved in chewing/mastication

Open mouth:
-lateral pterygoid: comes off of process of sphenoid bone and anchors to the articular disk of the TMJ

***innervated by CN5 (if damaged, have trouble closing mouth tightly or opening the mouth)

Question 5

How do the muscles of the TMJ move?

Answer 5

Close mouth muscles act as a “sling” to close the mouth

Open mouth muscle attaches to the disk and translates to pull the jaw anterior over the tubercle

Question 6

What would happen during TMJ dysfunction?

Answer 6

The mechanics of the articular discs will be disrupted causing “sticking” of the jaw when opening the mouth or hearing a clicking or popping sound