Ch 14 - TMJ

Prime movers of depression of mandible?

lateral pterygoid (1)

lateral deviation of the mandible to the left involves both spinning and gliding motions. Describe how that happens?

left condyle spins in the mandibular socket while the right condyle slides forward

normal resting position of the mandible

lips closed teeth several mm apart low level of activity in the temporals muscles mouth open far enough to fit 2 - 3 fingers between the front upper and lower teeth

postglenoid tubercle of the temporal bone

makes up the posterior wall of the fossa

where is the condyle of the mandible when @ rest?

mandible is seated in the mandibular fossa of the temporal bone

what is shaped like a horse-shoe and articulates with the temporal bone on each side?

mandibular bone

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (a) - the biting action requires what motion of TMJ?

mandibular depression

Forming the letter O with your lips requires what motion of TMJ and contraction of what muscle that flattens your cheek?

mandibular depression & buccinator muscle

TMJ muscle fibers running more vertically, tend to create what?

mandibular elevation & depression

Name the 2 bones and their articular surfaces that make up the TMJ

mandibular fossa of temporal bone & condyle of mandible

what is the TMJ made up of?

mandibular fossa of the temporal bone superiorly, articulating with the condyle of the mandible inferiorly

TMJ muscle fibers running more horizontally, will tend to create what?

mandibular protrusion and retrusion (due to better alignment)

which is basically the return to anatomical position from a protruded position

mandibular retrusion

what muscles make up the fullness of the posterior portion of the cheek?

masseter

Prime movers of contralateral lateral deviation of the mandible?

medial pterygoid, lateral pterygoid

clenching your teeth requires what TMJ motion and involved what muscles?

motion: mandibular elevation muscle: temporalis, masseter, medial pterygoid

what motions occur in lateral movement?

one condyle rotating in the mandibular fossa the other condyle glides foreword

mandibular depression

opening the mouth

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (b) - which side of the jaw experiences some distraction?

opposite side of bread

stylomandibular ligament

plays a role in limiting extensive anterior motion

mastoid process of the temporal bone

posterior and inferior to external auditory meatus which digastric muscle attaches

in what plane does mandibular elevation and depression occur?

sagittal plane

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (c) - which side of the jaw experiences some compression

same side as the bread

mandibular lateral deviation

side to side jaw movement

grinding your teeth could involve motions in the sagittal plane and frontal plane. What are these motions?

side-to-side motion = lateral deviation anterior/posterior motion = protraction and retraction

what type of joint is the TMJ

synovial (with a "modified hinge shape." It allows some gliding motion, but not a true hinge joint)

what muscle can be palpated superior and anterior to the ear?

temporalis

the main muscles used with TMJ movement include: (4)

temporalis masseter medial pterygoid lateral pterygoid

Prime movers of elevation of mandible?

temporalis masseter medial pterygoid (3)

Prime movers of Ipsilateral lateral deviation of the mandible?

temporalis & masseter

Prime movers of Retrusion of mandible?

temporalis (posterior)

body of the mandible

the horizontal portion of the lower jaw holds the lower teeth

what happens when you move the mandible laterally toward the left?

the left condyle will rotate and the right condyle will glide forward

What is another term for "adam's apple"

thyroid cartilage

Which nerve innervated the TMJ muscle?

trigeminal

what movements occur with protrusion and retrusion?

upper joint space condyle & disk move as one unit against the fossa and articular tubercle of the temporal bone no rotation, just forward/backward which are all equal

what 2 movements occur with elevation of the mandible?

upper joint space: articular disk and condyle glide posteriorly and superiorly lower joint space: condyle rotates on the disk, creating a posterior glide

ramus

vertical portion of the mandible (think jaw line)

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (g) - how does this change the amount of force the muscles need to generate in order to bite through the bread?

when biting with front teeth (long resistance arm), more force must be used to overcome the larger resistance

articular tubercle of the temporal bone

when the mandibles depressed, the condyle rests under this

the zygomatic arch is made up of which 2 bones?

zygomatic and temporal bones

where does the rotation of the condyle with lateral movement in the mandible occur?

around a vertical axis

which is more firmly attached to the mandible? the articular disk or temporal bone?

articular disk it allows the disk to move forward with the condyle of the mandible when the mouth opens and returns posteriorly when the mouth closes

important landmarks of the temporal bone

articular tubercle mandibular fossa postglenoid tubercle styloid process mastoid process external auditory meatus zygomatic process

mandibular fossa of the temporal bone

articulates with the condyle ("articular fossa")

condyle of the mandible

articulates with the temporal bone (also called "condylar process")

suprahyoid and infrahyoid are _____________ in TMJ movement

assisting muscles

mental spine of the mandible

attachment point for geniohyoid muscle

coronoid process of the mandible

attachment point for the masseter muscle

zygomatic process of the temporal bone

attachment site for the masseter

styloid process of the temporal bone

attachment site for various muscles and ligaments

what muscles work like a pulley?

digastric and omohyoid

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (f) - what would happen to the force and resistance arms if the bread was moved to the front teeth instead?

force arm would stay the same because the muscle attachments and joint axis haven't moved resistance arm would increase as the distance between joint axis and resistance has gotten longer

which plane do retrusion and protrusion occur in?

horizontal plane

Prime movers of Protrusion of mandible?

lateral & medial pterygoid

lateral ligament

"temporomandibular ligament" limits downward, posterior, and lateral motions of the mandible

Trigeminal Nerve

#5 Both Sensory --> facial area Motor --> chewing muscles

Facial Nerve

#7 Both Sensory --> tongue area Motor --> face muscles

two motions occur during mandibular depression: (1.) disk and condyle glide forward & inferiorly. (2.) mandible rotates anteriorly anteriorly on the disk. Which occurs first?

(2) anterior rotation of the mandibular condyle on the disk

mandibular protrusion

(protraction) moving the jaw forward

mandibular retrusion

(retraction) moving jaw posteriorly

sit in a good posture position with your thumb beneath your chin. open your mouth against slight pressure. - what is the joint motion? - what type of muscle contraction (isometric, concentric, or eccentric) is occurring? - name the primary muscle responsible for moving the mouth - name the muscle group that assists with this action - TMJ muscles in what group are acting as stabilizers during this activity? describe what structure they are stabilizing and what motion they are preventing.

- mandibular depression -concentric - lateral pterygoid - lateral pterygoid - lateral pterygoid and suprahyoid group - infra hyoid group contracts to stabilize hyoid and prevent it form elevating when suprahyoid group contracts

sit in a good posture position with your hands on each side of the jaw. move your jaw from side to side against slight resistance. - what is the joint motion? - what type of contraction (isometric, concentric, eccentric) is occurring? -name the muscles responsible for moving the jaw to the right

- mandibular latereal deviation - concentric - right temporalis and masseter, left medial and lateral pterygoid

what 2 motions occur for depression of the mandible

1. lower joint space convex-on-concave mandibular condyle rotates on disk creating anterior glide of condyle, distal end (ramus/angle) moves posteriorly 2. occurs in the upper joint space gliding the disk forward and downward under the articular tubercle

TMJ consists of:

2 bones 1 disk diving joint into 2 joint spaces 1 joint capsule 4 ligaments 4 main muscles 5 movements

what does the articular disk divided the joint space into?

2 separate compartments: large upper joint space and small lower joint space

what are some important bone markings of the mandible?

angle body condyle coronoid process mental spine neck notch ramus

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (e) -what class lever system is the TMJ functioning as?

3rd

biting off a tough piece of bread is usually done by placing it in one side of the mouth. (d) - identify force and resistance in this example

F = muscles R = bread

Lateral Pterygoid muscle

O - lateral pterygoid plate and greater wing of sphenoid I -mandibular condyle and articular disk A - bilaterally; depression, protrusion. Unilaterally' contralerbl lateral deviation N - Trigeminal (#5)

Medial Pterygoid Muscle

O - lateral pterygoid plate of sephnoid bone & tuberosity of maxilla I - ramus & angle of mandible A - bilaterally; elevation & protrusion. Unilaterally; contralateral lateral deviation N - trigeminal (#5)

Temporalis muscle

O - temporal fossa I - coronoid process and ramus of mandible A - bilaterally; elevation, retrusion N - trigeminal nerve (#5)

Masseter muscle

O - zygomatic arch of temporal bone & zygomatic process of maxilla I - angle of ramus and coronoid process of mandible A - bilaterally; elevation & unilaterally; ipsilateral lateral deviation N - trigeminal nerve (#5)

what portion of the Temporalis is the most effective line of pull when biting down hard and why?

anterior fibers because they are oriented more vertically

2 assistive muscle groups with TMJ movement includes:

Suprahyoid Group: mylohyoid geniohyoid stylohyoid digastric Infrahyoid Group: sternohyoid sternothyroid thyrohyoid omohyoid

sphenomandibular ligament

Suspends the mandible and limits excessive anterior motion

which would impair function of the TMJ more: damage to the mandibular deviation of CN #5 (Trigeminal, V) or damage to CN #7 (facial, VII)?

Trigeminal (5th)

smaller lower joint space

concave, accommodates the convex surface of the condlyle and allows joint to remain compatible throughout motion

as you stand in anatomical position, what TMJ muscles are working to resist the force of gravity? how are they contracting?

all muscles of mandibular elevation (temporalis, masseter, and medial pterygoid) are contracting isometrically

angle of the mandible

between body & ramus; joins these 2 landmarks (also called "angle of the ramus")

what is the mandibular bone comprised of?

body & 2 upwardly projecting rami (one on each side) each lateral end articulates with a different temporal bone, forming 2 identical joints on either side

what are the 2 parts of the skull

bones of the large cranium cavity (encases brain) bones of the face

mandibular elevation

closing the mouth

larger upper joint space

concave and convex to accommodate shape of the fossa