Muscles Of Mastication

Question 1

What are the muscles that elevate the mandible

Answer 1

Medial pterygoid, temporalis, superior lateral pterygoid, masseter

Question 2

What is the origin and insertion of the masseter

Answer 2

Superficial: anterior 2/3 of inferior border of zygomatic arch to angle of mandible and lateral lower aspect of ramus

Deep: posterior 1/3 of inferior border of zygomatic arch, fibres run vertically to insert onto lateral aspect of ramus above angle of mandible

Question 3

What are the actions of the masseter

Answer 3

Elevate mandible (bilateral contraction)

Protrusion by superficial fibres

Retrusion by deep fibres

Ipsilateral excursion during unilateral contraction

Question 4

What structures run superficial to the masseter

Answer 4

Facial nerve, transverse facial artery, facial process of parotid gland

Question 5

What is the origin and insertion of temporalis

Answer 5

Origin: inferior temporal line. Lies at temporal fossa
Insertion: anterior medial aspect of ramus and external oblique ridge of ramus

(Run deep to zygomatic arch)

Question 6

What is the action of temporalis

Answer 6

Elevate the mandible. Anterior fibres cause protrusion. Posterior fibres cause retrusion. Ipsilateral excursion

Question 7

What is the insertion and origin of the medial pterygoid

Answer 7

Medial surface of lateral pterygoid plate to medial aspect of ramus

Question 8

Action of medial pterygoid

Answer 8

Elevate the mandible. Contralateral excursion. Protrusion

Question 9

Insertion and origin of lateral pterygoid

Answer 9

Inferior: lateral aspect of lateral pterygoid plate to articular disc and fibrous capsule and pterygoid fovea

Superior: inferior aspect of greater wing of sphenoid to pterygoid fovea

Question 10

Action of lateral pterygoid

Answer 10

Superior: elevation
Inferior: depression, contralateral excursion and protrusion

Question 11

Nerve and blood supply to masseter

Answer 11

Masseteric artery branch of maxillary and transverse facial artery branch of superficial temporal artery

Trigeminal nerve, mandibular nerve, masseteric nerve

Question 12

Nerve and blood supply to temporalis

Answer 12

CNV3, deep temporal nerve

Deep temporal artery anastomose with middle temporal artery

Question 13

Nerve and blood supply to medial pterygoid

Answer 13

Pterygoid branch of maxillary artery

Medial pterygoid nerve branch of CNV3

Question 14

Nerve and blood supply to lateral pterygoid

Answer 14

Pterygoid branch of maxillary artery

Lateral pterygoid nerve branch of CN V3

Question 15

Name 3 accessory muscles that help to depress the mandible as well as their origins and insertions

Answer 15

Geniohyoid: genial tubercle/inferior mental spine to hyoid

Mylohyoid: mylohyoid line of mandible to hyoid bone

Anterior digastric: digastric fossa at mandible to intermediate tendon

Question 16

What is esophageal dysphagia and what are 3 possible causes

Answer 16

Sensation of food getting stuck at base of throat/chest

1. Narrowing of esophagus due to scar tissue due to GERD, trapping large pieces of food
2. Radiation therapy
3. Achalasal, lower esopheageal sphincter does not relax properly to let food enter stomach

Question 17

What is oropharyngeal dysphagia and 3 possible causes

Answer 17

Sensation of food going down windpipe or up your nose

1. Neurological disorder leading to weakening of throat muscles
2. Cancer
3. Zneker’s diverticum, a small pouch just above esophagus that colelcts food particles in throat

Question 18

What happens if gloosopharyngeal nerve is damaged

Answer 18

Decreased sense of taste posterior 1/3 of tongue

Diminished gag reflex

Weak cough reflex

Question 19

What happens if facial nerve damage

Answer 19

Paralysis of facial muscles. Eye cannot shut properly. Droopy lower eye lid, lacrimal fluid pools and is unable to spread around eye; cannot remove debris leading to ulceration

Poor lip strength. Mouth sag to opposite side when smiling

No taste in anterior 2/3

Dry mouth

Diminished jaw opening and closing

Question 20

What happens if hypoglossal nerve is damaged

Answer 20

Speech difficulties

Unable to position food for chewing, food get pocketed in cheeks