What does the TMJ allow the jaw to do? What is the TMJ formed of?
Allows opening, closing and a side to side movement of mouth
TMJ formed by articulation of temporal bone of cranium and the mandible.
What are 3 articulations in the TMJ?
Anterior tubercle of the squamous temporal bone
Head of mandible
Describe the nature of the TMJ joint
Unique mechanism – articular surfaces of bone never in contact with each other and separated by an articular disk, splitting joint into two synovial joint cavities each lined by a synovial membrane
What is the articular disk made of?
Dense fibrous CT with the same composition of fibrocartiliage lining articulatory surfaces
What muscles are reponsible for protrusion and retraction of the mandible?
Lateral pterygoid muscle – protrusion
Geniohyoid and digastric muscle – retraction
What muscles are responsible for elevation and depression of the mandible?
Depression caused mostly by gravity. If there is resistance, digastric, geniohyoid and mylohyoid muscles assist.
Elevation is caused by contraction of temporalis, masseter, and medial pterygoid.
What happens in a dislocation of the TMJ? What nerves run close to the joint and could be injured via trauma?
Head of mandible slips out of mandibular fossa and is pulled anteriorly. Patient unable to close mouth
Facial and auriculotemporal nerves
Why is an infection of the pterygoid region a danger to the eye?
pterygoid venous plexus connects to opthalmic and anterior facial veins. Pus inside pterygoid venous plexus raises pressure inside opthalmic veins or lead to cavernous sinus thrombosis, resulting in paralysis of extraocular muscles