Muscles of mastication and the movement of the tongue

Question 1

What are the three main glands and what type of acini are they made up of?

Answer 1

Parotid = serous acini
Submandibular = mixed 
Sublingual = mucous

Question 2

What structures run through the parotid gland? Why should surgeons be careful and what innervates it?

Answer 2

The parotid gland is the largest, it contains serous acini and has the facial nerve running through it where the nerve branches into three terminal branches therefore surgeons have to be very careful. The glossopharyngeal nerve innervates the parotid gland. It likes on top of the masseter and also the external carotid artery ascends through it.

Question 3

What is mumps? And how is it spread?

Answer 3

Mumps is caused by inflammation of the parotid glands caused by a very contagious viral infection.

Question 4

How are serous and mucous acini seen under a microscope?

Answer 4

The serous acini stain more and will appear more red whereas the mucous acini do not stain as well and appear more pale

Question 5

What is the TMJ and what happens there?

Answer 5

It is the temporomandibular junction. This is where the movement of the mandible occurs between the condyle of the mandible in the mandibular fossa of the squamous portion of the temporal bone.

Question 6

What is the articular disk?

Answer 6

The articular disk is a piece of fibrocartilagenous tissue that has no vascular connection or nerve innervation which sits in-between the condyle and the fossa in the temporal bone. It follow on from the lateral pterygoid muscle tendons.

Question 7

What happens to the disk in mandibular depression?

Answer 7

Firstly the articular disk remains in the mandibular fossa for small rotation of the mandible but then requires translation into the articular eminence for full mandibular depression.

Question 8

Problems with the TMJ?

Answer 8

In clicking jaw, the disk gets displaced anteriorly causing the posterior retrodiscal tissue to be pulled in between to the two bones upon opening the jaw. When opening the jaw, the condyle has to jump over the back end of the disk and when closing causes clicking when the condyle does back into the fossa.

Question 9

What is the significance of a locked jaw?

Answer 9

The is when the condyle is stuck behind the back end of the disk and therefore the condyle can not translate on the articular eminence.

Question 10

What nerve is common with all the muscles of mastication?

Answer 10

The mandibular branch of the trigeminal nerve (CN V3) which innervates all muscles of mastication

Question 11

Temporalis muscle? O, I, A

Answer 11

O = Temporal line in the temporal bone
I = Coronoid process of the mandible
A = Elevate and retract the mandible

Question 12

Masseter muscle? O, I, A

Answer 12

O = Zygomatic arch 
I = Mandibular ramus 
A = Elevate and protract the mandible

Question 13

Lateral pterygoid muscle? O, I, A

Answer 13

O = Lateral surface of the lateral pterygoid plate
I = Neck of the mandible and the condyle (articular disk)
A = Protract and depress the mandible and lateral deviation

Question 14

Medial pterygoid muscle? O, I, A

Answer 14

O = Medial surface of the lateral pterygoid plate
I = Inner surface of the mandibular ramus (follows the masseter)
A = Elevate and protract the mandible and lateral deviation

Question 15

What nerve is common with muscles of the tongue?

Answer 15

The hypoglossal nerve (CN XI)

Question 16

Genioglossus muscle?

Answer 16

Originates from the chin and forms a broad fan shape and makes up the most of the tongue. Acts to depress and protract the tongue.

Question 17

Hyoglossus muscle?

Answer 17

Originates from the hyoid bone and acts to depress and retract the tongue

Question 18

Styloglossus muscle?

Answer 18

Originates from the styloid process and acts to elevate and retract the tongue

Question 19

Palatoglossus muscle?

Answer 19

Originates from the palatine bones and acts to raise the back of the tongue and is also innervated by the VAGUS nerve