Lecture 2- Muscles of Mastication

Question 1

how many maxillary bones are there and what fuses them together

Answer 1

-2 maxillary bones
-fused together at the mid-palatal suture

Question 2

what is the superior border of the maxilla

Answer 2

floor of the nasal cavity and orbit

Question 3

what is the inferior border of the maxillar

Answer 3

palate and alveolar ridge

Question 4

what are the components of the maxilla

Answer 4

-body
-zygomatic process
-frontal process
-alveolar process
-palatine process

Question 5

what is the largest and strongest bone on the skull

Answer 5

the mandible

Question 6

what is the superior aspect of the mandible

Answer 6

alveolar crest and teeth

Question 7

what is the posterior aspect of the mandible

Answer 7

-mandibular angle
-ascending ramus
-coronoid process
-condyle

Question 8

what does the condyle articulate with

Answer 8

the cranium

Question 9

what is the medoilateral length of the condyle

Answer 9

15-20 mm

Question 10

what is the anterior-posterior width of the condyle

Answer 10

8-10 mm

Question 11

what does the squamous portion of the temporal bone articulate with

Answer 11

the mandibular condyle

Question 12

what is the articular eminence of the temporal bone

Answer 12

thick dense bone to tolerate heavy forces

Question 13

what are the muscles of mastication

Answer 13

-lateral pterygoids
- medial pterygoids
- temporalis
-masseter

Question 14

what direction do fibers of the superficial masseter and deep masseter run

Answer 14

-superficial: fibers run downwards and backwards
-deep: vertical

Question 15

what is the origin and insertion of the masseter

Answer 15

-origin: zygomatic arch
-insertion: lateral surface of ramus and angle of mandible

Question 16

what are the actions of the masseter

Answer 16

-elevates the mandible
-provides force for chewing
-superficial head: aids in protrusion
- deep head: stabilizes the condyle against the eminence

Question 17

what is the blood supply to the masseter

Answer 17

muscular branch of the maxillary artery

Question 18

what innervates the massester

Answer 18

masseteric nerve of mandibular division of the trigeminal nerve

Question 19

what are the 3 divisions of the temporalis and what direction do the fibers run

Answer 19

-anterior- vertical directed fibers
- middle- oblique across lateral aspect of the skull
- posterior: horizontal fibers come forward above the ear to join other temporalis fibers

Question 20

what is the origin and insertion of the temporalis

Answer 20

-origin: temporal fossa and lateral surface of the skull
- insertion: coronoid process and anterior border of ascending ramus

Question 21

what are the actions of each division of the temporalis

Answer 21

-anterior: mandible is raised vertically
- middle: elevates and retrudes the mandible
- posterior: aids in retrusion of the mandible

Question 22

what is the blood supply and nerve supply of the temporalis

Answer 22

-blood: a muscular branch of the maxillary artery
- nerve: deep temporal nerve of the mandibular division of trigeminal nerve

Question 23

what are the 2 heads of the lateral pterygoid

Answer 23

-superior lateral pterygoid
- inferior lateral pterygoid

Question 24

what is the origin and insertion of the inferior lateral pterygoid and where does it extend

Answer 24

• origin: outer surface of lateral pterygoid plate
• insertion: neck of condyle
  extends: backwards upwards and outwards

Question 25

what are the actions of the inferior lateral pterygoid

Answer 25

-bilateral contraction: causes the condyle to be pulled down the articular eminence and the mandible is protruded - unilateral contraction: causes mediotrusive movement - downward, forward and medially

Question 26

what is the origin and insertion of the superior lateral pterygoid

Answer 26

- origin: infratemporal surface of the greater sphenoid wing - insertion: disk , capsule, and neck of the condyle

Question 27

what belly is smaller in the lateral pterygoid

Answer 27

superior lateral

Question 28

what are the actions of the superior lateral pterygoid

Answer 28

-inactive during mandibular opening - active only with elevator muscles (closing of the mandible) - power stroke: this muscle is active during mandibular closure against resistance (chewing or clenching)

Question 29

what is the blood and nerve supply to the lateral pterygoid

Answer 29

-blood: a muscular branch of the maxillary artery - nerve: a branch of the masseteric or buccal nerve of the mandibular division of the trigeminal nerve

Question 30

what is the origin and insertion of the medial pterygoid

Answer 30

-origin: pterygoid fossa - insertion: medial surface of the mandibular angle

Question 31

what are the functions of the medial pterygoid

Answer 31

- elevates the mandible - protrudes the mandible -unilateral contractions results in mediotrusion

Question 32

what is the blood and nerve supply to the medial pterygoid

Answer 32

-blood: a muscular branch of the maxillary artery - nerve: a motor branch of the mandibular division of the trigeminal nerve which reaches the posterior border of the muscle near the base of the skull

Question 33

what muscles make up the masseter sling

Answer 33

masseter and medial pterygoid

Question 34

what muscles make up the suprahyoids

Answer 34

-geniohyoid - mylyhyoid -digastric -stylohyoid

Question 35

what are the functions of the suprahyoids

Answer 35

-elevate hyoid bone and depresses the mandible when hyoid bone is fixed

Question 36

what is the origin and insertion of the geniohyoid

Answer 36

origin: inferior genial tubercle on the inner surface of the mandibular symphysis insertion: anterior surface of body of hyoid bone

Question 37

what is the origin and insertion of the mylohyoid

Answer 37

origin: line from last molar root to mandibular symphysis insertion: median raphe from chin to hyoid bone

Question 38

what are the 2 bellies of the digastric

Answer 38

anterior and posterior

Question 39

what is the origin and insertion of the digastric

Answer 39

origin: the posterior belly, longer than the anterior, arises from the mastoid process. the anterior belly arises from a depression on the inner side of the lower border of the mandible, close to the symphysis insertion: hyoid bone

Question 40

what muscles contract during depression of the mandible

Answer 40

-inferior lateral pterygoid -digastric

Question 41

what muscles relax during depression of the mandible

Answer 41

-masseters -medial pterygoids - temporalis

Question 42

what muscles contract during elevation of the mandible

Answer 42

-masseters - medial pterygoid - temporalis -superior lateral pterygoid

Question 43

what muscles relax during elevation of the mandible

Answer 43

-inferior lateral pterygoid - digastric

Question 44

what muscles are contracting and relaxing during right lateral movement

Answer 44

contraction: left inferior lateral pterygoid relaxation: right inferior lateral pterygoid and slight relaxation of elevators

Question 45

what contracts and relaxes during left lateral movement

Answer 45

contraction: right inferior lateral pterygoid relaxation: left inferior lateral pterygoid, slight relaxation of elevators

Question 46

what contracts during protrusion

Answer 46

mainly inferior lateral pterygoids assisted by masseters and medial pterygoids

Question 47

what is contracting during retursion

Answer 47

temporalis