Muscles of Masstification

Question 1

what are the muscles of mastication?

Answer 1

1. temporalis
2. masseter
3. medial pterygoid
4. lateral pterygoid

Question 2

what is the origin of the lateral pterygoid?

Answer 2

superior: lateral surface of greater wing of sphenoid
inferior: lateral surface of pterygoid plate

Question 3

what is the insertion of the lateral pterygoid?

Answer 3

superior: articular disc and capsule of TMJ
inferior: superiomedial surface of ramus, and condylar process of mandible

Question 4

what is the action of the lateral pterygoid?

Answer 4

bilateral: protrudes (protracts) mandible (pulls disc forward). depresses (abducts) mandible
unilateral: lateral movements (excursion) of mandible (chewing). if one side is injured the jaw will deviate toward the injured side.

Question 5

what is the only muscle of mastication that does NOT elevate the mandible?

Answer 5

lateral pterygoid

Question 6

what is the innervation of the lateral pterygoid?

Answer 6

CN V3

Question 7

what is the origin of the medial pterygoid?

Answer 7

superficial: maxillary tuberosity
deep: medial surface of lateral pterygoid plate, lateral surface of medial pterygoid plate, pterygoid fossa

Question 8

what is the insertion of the medial pterygoid?

Answer 8

both superficial and deep insert into the medial surface of the ramus and angle of the mandible

Question 9

what are the actions of the medial pterygoid?

Answer 9

elevates (adducts) mandible
protrudes (protracts) mandible
unilateral: lateral movements (excursion) of mandible

Question 10

what is the innervation of the medial pterygoid?

Answer 10

CN V3

Question 11

what is unique about the medial pterygoid?

Answer 11

it is the deepest muscle of mastication

Question 12

what are the different portions of the temporalis, and which types of fibers do they have?

Answer 12

anterior: vertical fibers
middle: oblique fibers
posterior: horizontal fibers

Question 13

what is the origin of the temporalis?

Answer 13

inferior temporal line of the temporal fossa

temporal fascia

Question 14

what is the insertion of the temporalis?

Answer 14

it travels UNDER the zygomatic arch and inserts into:
coronoid process of mandible
anterior border of ramus of mandible

Question 15

what are the actions of the temporalis?

Answer 15

vertical: elevate (adduct) mandible
middle and posterior: retrude (retract) mandible
unilateral: lateral movement (excursion) of mandible

Question 16

what is the innervation of the temporalis?

Answer 16

CN V3

Question 17

what is unique about the temporalis?

Answer 17

it is the main postural muscle - maintains the mandible in the resting position

Question 18

what are the portions of the masseter and how are their fibers oriented?

Answer 18

superficial: larger part, fibers run downward and slightly backward
deep: smaller part, fibers run vertically

Question 19

what is the origin of the masseter?

Answer 19

superficial: anterior 2/3 of zygomatic arch
deep: posterior 1/3 of zygomatic arch

Question 20

what is the insertion of the masseter?

Answer 20

superficial: lateral surface of angle and ramus of mandible
deep: ramus and coronoid process of mandible

Question 21

what are the actions of the masseter?

Answer 21

elevate (adduct) mandible
protrude (protract) mandible - superficial head
unilateral: lateral movement (excursion) of mandible

Question 22

what is the innervation of the masseter?

Answer 22

CN V3

Question 23

what passes superficial to the masseter?

Answer 23

parotid duct
transverse facial artery
branches of CN VII