TMJ and Muscles of Mastication Flashcards
what is the function of the condylar process
its the articular process of the TMJ
where does the nerve and vessels to the masseter muscle pass through on the mandible
the mandibular notch
what is the mandibular symphis
where the two halves of the mandible have fused
where is the IAN and its associated artery and vein housed
mandibular foramen
what is the relevance of the mylohyoid line with regards to infections and what condition can this cause
infections in lower teeth may spread to below mylohyoid line and into flood of the mouth and submandibular region (LUDWIG’S ANGINA)
where does the nerve to the mylohyoid branch off from the IAN
the mylohyoid groove
what comprises the TMJ
the mandibular fossa of temporal bone and condylar process of mandible
what type of joint is the TMJ
a modified hinge (atypical) synovial joint
what are the articular surfaces of the TMJ covered with
fibrocartilage
what type of dislocation in the TMJ is most common
anterior
how many ligaments are in the TMJ
3 (2 extrinsic and 1 intrinsic)
what are the functions of the TMJ ligaments
connect mandible to cranium
what are the two extrinsic ligaments
sphenomandibular and stylomandibular
what ligament provides passive support to the mandible and runs from the spine of sphenoid to the lingula
sphenomandibular ligament
what ligament is a thickening of the capsule of the parotid and runs from the styloid process to angle of the mandible and is not consider to contribute to strength
stylomandibular ligament
what is the function of the lateral ligament
strengthens TMJ laterally
how many types of movements can the mandible produce and what are they
5 - protrusion, retraction, elevation, depression and lateral
what muscles aid the protrusion of the mandible
lateral pterygoid and medial pterygoid
what are protrusive and retractive movements
gliding movement between temporal bone and articular disc
what muscles aid in retraction of the mandible
posterior fibres of temporalis, deep part of masseter and geniohyoid and digastric
what muscles aid in elevation of the mandible
temporalis, masseter and medial pterygoid
what muscles aid in depression of the mandible
digastric, geniohyoid and mylohyoid
what are elevation/ depression movements
hinge and rotational movements between head of mandible and articular disc
what are lateral movements and what muscles aid in this
grinding and chewing and this is aided by temporalis on the same side and pterygoids on opposite side
when is TMJ most unstable
during depression as the condylar process moves anteriorly and lies under the articular eminences with mandibular head vulnerable to anterior dislocation
what is the position of the mandible at rest
the heads of mandible are held in a retracted position in the mandibular fossae and chin is elevated by tonus of the retractors and elevators of mandible
how does anterior dislocation of the mandible occur
through excessive contraction of lateral pterygoids through yawning (or sometimes a punch to the chin when the mouth is open)
what occurs when the TMJ is dislocated
the mandible remains depressed and the person cant close their mouth
why is posterior dislocation uncommon
it is resisted by postglenoid tubercle and strong intrinsic lateral ligament
what occurs when there is injury to the articular branches of auriculotemporal nerve supplying the TMJ
laxity and instability of TMJ
what muscles are involved in elevation of mandible
temporalis, masseter and medial pterygoid
what muscles are involved in depression of the mandible
lateral pterygoid, suprahyoid and infrahyoid muscles
what muscles are involved in protrusion of the mandible
lateral pterygoid, masseter and medial pterygoid
what muscles are involved in retrusion of the mandible
temporalis
what pharyngeal arch are the muscles of mastication derived from
first pharyngeal arch
what is the origin and insertion of the temporalis
O = temporal fossa and fascia
I = coronoid process of mandible and anterior border of ramus
what is temporalis innervated by
deep temporal nerves from anterior trunk of CN V3
what is the origin and insertion of the superficial part of the masseter
O = maxillary process of zygomatic bone and anterior 2/3rd of inferior border of zygomatic arch
I = angle and lateral surface of ramus of mandible
what is the masseter innervated by
masseteric nerve from anterior trunk of CN V3
what is origin and insertion points of the superficial head of the medial pterygoid
O = maxillary tuberosity and pyramidal process of palatine bone
I = angle of mandible
what is the origin and insertion points of the deep head of the medial pterygoid
O = medial surface of lateral pterygoid plate
I = medial surface of ramus
what is the medial pterygoid innervated by
nerve to the medial ptergoid from main trunk of CN V3
what is the origin and insertion point of the upper head of lateral ptergoid
O = infratemporal surface of greater wing of sphenoid bone
I = capsule of TMJ and articular disc
what is the origin and insertion points of the lower head of the lateral pterygoid
O = lateral surface of lateral pterygoid plate
I = front of the neck of the mandible (pterygoid fovea)
in relation to muscles of mastication, what can cause trismus
an IAN block piercing the medial pterygoid causing it to contract reflexively and close the mouth
what is the lateral pterygoid innervated by
nerve to the lateral pterygoid and buccal nerve from anterior trunk of CN V3
