TMJ and muscles of mastication

Question 1

TMJ

Answer 1

articulation between mandible and skull

modified hinge joint:

1. articular eminence and tubercles of temporal bone
2. mandibular fossa of temporal bone
3. condyle of mandible

Question 2

Mandibular fossa

Answer 2

1. Receives mandibular condyle
2. Articular surface covered with dense fibrous tissue
3. Borders of mandibular fossa

Question 3

Borders of mandibular fossa

Answer 3

Lateral
-Zygomatic process of temporal bone

Medial: spine of sphenoid bone

Anterior: articular eminence

Posterior: squamotympanic and petrotympanic fissures

Question 4

Squamotympanic fissure

Answer 4

separates mandibular fossa of squamous portion of temporal bone from tympanic plate of temporal bone

Question 5

Petrotympanic fissure

Answer 5

adj to small wedge of petrous temporal bone

*CHORDA TYMPANI PASSES THROUGH PETROTYMPANIC FISSURE

Question 6

Mandibular condyle

Answer 6

Roller shaped w/ medial + lateral poles

• long axis of condyles angled posteriorly
• neck of condyle connects condyle to ramus of mandible

Question 7

Articular surface of condyle

Answer 7

covered with dense fibrous tissue w/ isolated groups of chondrocytes + little surrounding matrix,
reflecting formation by intramembranous ossification

Question 8

External oblique line

Answer 8

attachment for depressor anguli oris

Question 9

Gonial angle

Answer 9

Junction of posterior border of ramus and inferior border of body of mandible

Question 10

Antegonial notch

Answer 10

Junction of ramus and body of mandible

Question 11

Digastric fossa

Answer 11

Anterior internal aspect, above inferior border.

Small depressions, anterior belly of digastric

Question 12

Mental spine (genial tubercles)

Answer 12

Midline, superior to digastric fossae.
May be 4 or single fused spine
Genioglossus (upper aspect)
Geniohyoid (lower aspect)

Question 13

Mylohyoid ridge (line)

Answer 13

Runs obliquely from lateral aspect of digastric fossae to below lingual alveolar crest of last mandibularmolar
– origin of mylohyoid muscle

Question 14

Sublingual fossa

Answer 14

above mylohyoid line, accommodates sublingual gland

Question 15

Submandibular fossa

Answer 15

below mylohyoid line, submandibular gland

Question 16

Mandibular foramen

Answer 16

midpoint of ramus of mandible

Question 17

Mandibular canal

Answer 17

continuation of mandibular foramen, deep into mandible

• runs inferiorly and anteriorly through ramus and body just below roots of mandibular teeth and ends at midline.
• carries inferior alveolar n and artery to mandibular teeth
• cutaneous branches pass to facial aspect of mandible via mandibular foramen

Question 18

Lingula

Answer 18

guards superoanterior border of mandibular foramen
- sphenomandibular ligament attached
May interfere with anesthetic injections of inferior alveolar n at mouth of mandibular foramen

Question 19

Mylohyoid sulcus (groove)

Answer 19

runs downward and forward from inferior border of mandibular foramen.
* n to mylohyoid muscle

Question 20

Coronoid notch

Answer 20

Concavity on anterior border of ramus as it approaches body below

Question 21

Internal oblique line (temporal crest)

Answer 21

buttressing ridge of bone on internal surface of ramus

• slopes downward and forward
• as it goes to last molar, divides to pass around last molar, divisions becoming continuous with buccal and lingual alveolar crests
• enclosed triangle: retromolar triangle

Question 22

Retromolar fossa

Answer 22

depression between anterior border of ramus and temporal crest

Question 23

Articular disc

Answer 23

Bi-concave

• allows flexibility in disc so it can conform during TMJ motion
• allows disc to be self-centered

Question 24

Articular Disc Divisions

Answer 24

Divides joint into superior/inferior compartments

*disc attached to inner periphery of articular capsule by superior and inferior sheets or lamellae that continue superiorly and inferiorly to blend with walls of capsular ligament

superior lamella: elastic, inferior = collagen

Question 25

TMJ

Answer 25

like all synovial joints possesses fibrous capsule that encloses joint surface

Question 26

Capsular ligament, lateral/temperomandibular ligament

Answer 26

reinforcements of joint/intrinsic ligaments capsule region | - prevent excessive lateral movement and posterior dislocation

Question 27

Stylomandibular ligament

Answer 27

extrinsic ligament - runs from styloid process to angle of mandible limits protrusion

Question 28

Sphenomandibular ligament

Answer 28

Runs from spine of sphenoid to lingula of mandible - Supports weight of mandible - Prevents excessive lateral movements of mandible

Question 29

Movements of mandible

Answer 29

1. Elevation/depression - fulcrum located approximately at mandibular foramen 2. Protrusion/retrusion 3. Lateral excursion (deviation)

Question 30

Hinging and Gliding at TMJ

Answer 30

Most mandibular movement - Hinge movement takes place in LOWER joint compartment - Gliding (translation) in upper joint compartment - Upon opening, both condyle and disc translate forward to sit on articular eminence

Question 31

Muscles of mastication

Answer 31

1. Temporalis 2. Masseter 3. Lateral pterygoid muscle 4. Medial pterygoid muscle

Question 32

Temporalis muscle

Answer 32

Attachments: 1. temporal fossa 2. tip of coronoid process, ramus of mandible ``` Action: bilateral: elevation, REtrusion of mandible unilateral: ipsilateral deviation --holds resting position of mandible Inn: Deep temporal branches ```

Question 33

Masseter muscle

Answer 33

Attachments: - outer and inner surfaces of zygomatic bone and arch - angle and lateral surface of ramus of mandible Action: Bilat: elevation, PROtrusion of mandible Unilat: ipsilateral deviaion Inn: masseteric n

Question 34

Lateral ptyergotd muscle

Answer 34

Attachments: Superior head: greater wing of sphenoid Inferior head: lateral pterygoid plate Both: capsule, disc, condyle Action: Bilateral: depresses, protracts mandible Unilateral: contralateral deviation Inn: lateral pterygoid nerves

Question 35

Medial Pterygoid Muscle

Answer 35

Attachments: - Lateral pterygoid plate, tuberosity of maxilla - Medial ramus of mandible, inferior to mandibular foramen Action: Bilat: Elevation, PROtrusion Unilat; CONTRAlateral devision Inn: medial pterygoid nerve

Question 36

Nerve supply

Answer 36

Most of the TMJ supplied by sensory articular branches of auriculotemporal nerve - small anterior portion supplied by sensory fibers arising from masseteric branches of V3 -posterior and posterolateral regions of joint capsule contain free nerve endings - pain impulses from joint (protection against excessive mandibular movement) -retrodiscal inferior lamella has proprioceptive mechanoreceptors -detect condylar movement and position

Question 37

Blood supply

Answer 37

- Articular branches from superficial temporal a to supply most of the joint - A from muscular branches of maxillary artery that supply anterior aspect of joint

Question 38

Examination of TMJ

Answer 38

Palate area Muscles: temporalis and masseter TMJ movement: anterior: lateral aspect of TMJ palpated just anterior to ear. Pt opens/close while palpating bilaterally Posterior: finger inside ears and press gently anteriorly. Pt open/close several times, check for pain and equal motion bilaterally -Auscultation may assist in evaluation