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Head and Neck Anatomy > Muscles of Mastication > Flashcards

Muscles of Mastication Flashcards

1
Q

Temporal fossa

A

Area inferior to temporal lines as far as the zygomatic arch

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2
Q

Infratemporal fossa

A

Area just below the zygomatic arch and medial to the ramus of the mandible

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3
Q

Depression of the mandible

A

Lowering the mandible, opening the oral cavity. This is due to bilateral muscle contraction

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4
Q

Elevation of the mandible

A

Bringing the mandible superior from an inferior position. This is due to bilateral muscle contraction.

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5
Q

Protrusion of the mandible

A

Bringing the mandible forward, like a bulldog (underbite) - due to bilateral muscle contraction

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6
Q

Retrusion of the mandible

A

Bringing the mandible posteriorly, this is due to bilateral muscle contraction

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7
Q

What is the unilateral movement of the mandible?

A

Lateral excursions - swinging the mandible right or left.

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8
Q

What muscles influence mastication, although they are not technically muscles of mastication?

A

Syprahyoid muscles and infrahyoid muscles, also the posterior neck musculature

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9
Q

How do the suprahyoid muscles influence the muscles of mastication?

A

They cannot move the mandible by themselves, they are synergists, but they also move when the mandible moves

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10
Q

How do the infrahyoid muscles influence the muscles of mastication?

A

The infrahyoid, or strap muscles, cannot move the mandible themselves by will influence how it moves because they are a counterforce to the suprahyoid muscles - they will function in stabilization of the mandible

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11
Q

How many muscles make up the muscles of mastication?

A

8 total, or 4 pairs of muscles

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12
Q

Where do the muscles of mastication originate?

A

The base of the skull

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13
Q

Where do the muscles of mastication insert?

A

the ramus of the mandible

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14
Q

What is the nerve innervation of the muscles of mastication?

A

All of the muscles of mastication are innervated by branches of the mandibular division of the trigeminal nerve (V3)

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15
Q

What provides the blood supply to the muscles of mastication?

A

Branches of the maxillary artery, which will correspond to the name of the muscle that they are supplying

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16
Q

In what plane(s) are the muscle fibers of the muscles of mastication oriented?

A

All of the muscles of mastication have fibers that run in 3 planes
anterior to posterior
superior to inferior
lateral to medial

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17
Q

What is the origin of the masseter?

A

Superficial head originates from the lower border of the anterior 2/3 of the zygomatic arch

Deep head originates from the medial surface and lower border of the posterior 1/3 of the zygomatic arch

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18
Q

What is the insertion of the masseter?

A

Lateral aspect of the ramus and angle of the mandible

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19
Q

What is the MAIN action of the masseter, and what are its supporting actions?

A

Main action = elevator of the mandible due to its prominent fibers being oriented superior to inferior

Supporting actions = protrusion with the fibers oriented anterior to posterior, and lateral excursions to the ipsilateral side by way of the fibers oriented medial to lateral

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20
Q

The masseter is said to be a prominent _____________ muscle

A

Grinding - masseter is very big in people who grind their teeth

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21
Q

What is the origin of the temporalis muscle?

A

The entire temporal fossa that is inferior to the temporal line

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22
Q

What is the insertion of the temporalis?

A

Coronoid process of the mandible, and the temporal crest primarily on the medial surface (insertion can go all the way down to the 3rd molar region)

Long, broad insertion to the ramus; therefore it has a lot of control over the mandible

23
Q

What innervates the temporalis?

A

Anterior and posterior deep temporal nerves

24
Q

What supplies the temporalis?

A

Anterior and posterior deep temporal arteries

25
Q

What is the PRIMARY action of the temporalis?

A

Acts as an elevator of the mandible by way of the fibers that are oriented superior to inferior

26
Q

What is the ONLY muscle that can retrude the mandible?

A

The temporalis (posterior fibers ONLY!)

27
Q

What are the supporting actions of the temporalis muscle?

A

Lateral movement by pulling mandible to the ipsilateral (same) side
Retrusion by the posterior fibers only
It is also a postural muscle - the temporalis maintains the mandible in the rest position

28
Q

What is the origin of the medial pterygoid?

A

The medial surface of the lateral pterygoid plate

And the superficial head of the medial pterygoid comes from the maxillary tuberosity

29
Q

Where does the medial pterygoid insert?

A

Medial surface of the ramus of the mandible (pterygoid tubercle)

This is a broad attachment - it is basically the whole surface below the mandibular foramen

30
Q

What is the primary action of the medial pterygoid?

A

Primary action is elevation because the primary fibers are oriented superior to inferior

31
Q

What are the supporting actions of the medial pterygoid?

A

Protrusion (bringing mandible forward) and lateral movement to the CONTRALATERAL side

32
Q

Which head of the lateral pterygoid is larger?

A

The inferior head

33
Q

What is the origin of the inferior head of the lateral pterygoid?

A

Lateral surface of the lateral pterygoid plate

34
Q

What is the insertion of the inferior head of the lateral pterygoid?

A

Pterygoid fossa - anterior and medial surface of the neck of the mandible

35
Q

What is the origin of the superior head of the lateral pterygoid?

A

Infratemporal surface of the sphenoid bone - flat part of the sphenoid bone, lateral to the pterygoid process

36
Q

What is the insertion of the superior head of the lateral pterygoid?

A

The pterygoid fossa, and the TMJ joint capsule and articular disc

37
Q

What is the primary action of the lateral pterygoid?

A

Depression of the mandible because the primary fibers are oriented in an anterior to posterior direction

38
Q

What are the supporting actions of the lateral pterygoid?

A

Protrusion, lateral movement to the contralateral side, and the superior head will be active during closure to brace the condyle against the eminence for smooth retrograde translation of the joint

39
Q

What is the primary protruder of the mandible?

A

The lateral pterygoid

40
Q

Does the lateral pterygoid independently move the disc of the TMJ?

A

NO!

The lateral pterygoid helps to stabilize the joint but the two heads of the muscle cannot independently move the disc. The superior head of the lateral pterygoid is a CT attachment to the capsule of the TMJ, which is why it may seem like it can independently move the joint, but it CANNOT

41
Q

What is the dense network of veins surrounding the lateral pterygoid?

A

Pterygoid plexus

42
Q

What does the pterygoid plexus connect to directly?

A

The cavernous sinus - deep venous drainage of the face

43
Q

What is the reason that the branches of the mandibular division of the trigeminal nerve are intimately involved with the lateral pterygoid?

A

The foramen ovale lies just medial to the lateral pterygoid, and the trigeminal nerve passes through the foramen ovale so the branches of the mandibular division of trigeminal are so close

44
Q

What supplies the lateral pterygoid?

A

The maxillary artery, it may pass deep or superficial to the lateral pterygoid

45
Q

What muscle is prone to spasms, and why?

A

The lateral pterygoid, because it does not contain muscle spindles. This is thought to be related to TMD

46
Q

Masticator space

A

Fascial space enclosing the muscles of mastication and everything related to them

This fascia is continuous from temporalis around pterygoids up through all of masseter

47
Q

What are the bilateral movements of muscle pairs that open and close the mandible?

A

protrusion
retrusion
elevation
depression

48
Q

What is required in order to make lateral excursions of the mandible?

A

Unilateral contraction of muscles that pull the mandible to the desired side

49
Q

What is the rotating condyle?

A

the condyle in the fossa

50
Q

What is the orbiting condyle?

A

the condyle out of the fossa

51
Q

Condyle on side to which movement is directed

A

rotating condyle

52
Q

Condyle on opposite side, moves in an arc around the rotating condyle

A

orbiting condyle

53
Q

If you move the mandible to the right, what muscles are contracting?

A

The right masseter and temporalis because they move to the ipsilateral (same) side and then then left medial and lateral pterygoids because they move to the contralateral side

Head and Neck Anatomy (8 decks)

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