03-16: Muscles of Mastication

Question 1

SCALP

Answer 1

S = Skin
C = Connective Tissue (typically dense)
A = Aponeurosis (layers of flat broad tendons)
L = Loose tissue (adipose)
P = Periosteum

Question 2

Muscles of Expression (Nerve)

Answer 2

CN VII (Facial Nerve)

Question 3

Frontalis

Answer 3

Raises and lowers eyebrows

Question 4

Prosares

Answer 4

Furrows brow, crinkles nose, brings in eyebrows

Question 5

Orbicularis Occuli

Answer 5

Allows closing of eye, forceful closing of eye

Question 6

Levator Palpebrai

Answer 6

Elevates eyelid; Innervated by ocular motor, not affected by loss of CN VII

Question 7

Zygomaticus (Major and Minor)

Answer 7

Raises corners of mouth for smiling

Question 8

Risorius

Answer 8

“Fake smile” muscle; pulls corners/sides of mouth laterally; verticall pull

Question 9

Platysma

Answer 9

Tighterns up neck; the “frog” neck

Question 10

Orbicularis Oris

Answer 10

Puckers lips

Question 11

Buccinator

Answer 11

• Chewing: Keeps food in oral cavity by compressing cavity
• Sucking muscle: compresses cheeks , keeps food in, stimulates cognitive thinking
• Helps form angle of mandible

Question 12

Branches of facial nerve (CN VII)

Answer 12

Temporal, Zygomatic, Buccal, Mandibular, Cervical

Question 13

Divisions of Trigeminal Nerve (CN V)

Answer 13

V1 Ophthalmic (sensory) = C1
V2 Maxillary (sensory) = C2
V3 Mandibular (motor) = C3

Question 14

Movements of joint

Answer 14

• Depression (opening mouth)
• Mandibular elevation (closing mouth)
• Lateral deviation (side-to-side jaw movement)
• Protrusion (moving jaw forward)
• Retrusion (moving jaw backward)

Question 15

Translation (Angle of Mandible)

Answer 15

Ability of joint to slide down articulating eminence

Question 16

Rotation (Angle of Mandible)

Answer 16

Occurs in condylar disk joint (condyle of mandible) Clicking - can rotate, but comes off dis where it may be adhered

Question 17

Depression of mandible

Answer 17

• Anterior rotation of the mandiubular condyle on the disk

- Sliding of the disk and condyle forward and downward under the articular tubercle

Question 18

Elevation of mandible

Answer 18

• Sliding the disk and condyle posterior and superior

- Posterior rotation of condyle on the disk

Question 19

Protrusion/Retrusion

Answer 19

• Involves anterior/posterior movement, no rotation

- Condyle and disk move as one unit against the articular fossa of the temporal bone

Question 20

Lateral movement

Answer 20

One condyle rotates in the articular fossa while the other condyle slides forward

Question 21

Muscles of elevation (open mouth)

Answer 21

• Temporalis, Masseter

- Masseter is prime elevation muscle

Question 22

Lateral pterygoid

Answer 22

• Superior band works eccentrically to allow translation and control disk from slipping back
• Middle and inferior bands work concentrically to open mouth near condyle

Question 23

Actions of hyoid muscles

Answer 23

Suprahyoid - Mandibular depression

Infrahyoid - Active during swallowing

Question 24

Optimal opening of mouth

Answer 24

• 40mm

- 4:1:1 ratio (4mm of opening, 1mm of lateral excursion, 1mm of protrusion)

Question 25

Hypoglossal Nerve

Answer 25

Swallowing nerve

Question 26

Deflective

Answer 26

• Open up with deviation to one side and stays there

- One of the joints doesn’t open all the way

Question 27

Deviation

Answer 27

• Opens up, deviates to side, then comes back to midline

- Sign of muscle imbalance

Question 28

Craniovertebral Angle

Answer 28

Angle of the dens and the cranium sits at 101 degrees - change in angle affects lower c-spine position