L51. Larynx and Laryngopharynx

Question 1

Define the vertical borders of the larynx

Answer 1

Starts from epiglottis and continues to the top of trachea (lower border of cricoid cartilage/C6)

Question 2

Describe the shape and structure of the larynx

Answer 2

The larynx is a tube that is supported by a system of cartilages giving it its 3D shape.

It is open posteriorly at the superior part to the pharynx called the LARYNGEAL INLET that allows air to come in and out of the airways

Question 3

What are the main skeletal structures making up the larynx [4]?

Answer 3

1. Hyoid Bone
2. Epiglottis
3. Thyroid Cartilage
4. Cricoid Cartilage

Question 4

Describe the thyroid cartilage of the larynx

Answer 4

• Anteriorly, it has an angle (sharp projection sticking out and is palpable in the midline) called laryngeal prominence or adams apple.
• It has laminae laterally
• It has large projections that point upwards and downwards off the posterior aspect.
• It is open posteriorly for the laryngeal inlet (communication between pharynx and airways)

Question 5

Describe the cricoid cartilage

Answer 5

A completely closed ring of cartilage that encricles the whole top of the trachea.

It has a short anterior arch and tall posterior laminae

Question 6

What are the membranes connecting the major structures of the larynx?

Answer 6

1. Thyrohyoid membrane connecting the hyoid bone to the thyroid cartilage
2. Cricothyroid membrane connecting the inferior aspect of the thryoid bone to the superior aspect of the cricoid cartilage

Question 7

What is important about the posteriolateral aspect of the superior part of the cricoid cartilage?

Answer 7

It has small cartilages called Arytenoid cartilages which are pyramidal in shape.

• Each one has two major processes that project towards the front and midline
  
  • Vocal processes anteromedially that attach to vocal ligamants
  • Muscular processes laterally for muscle attachment.

Question 8

Describe the movements of the arytenoid cartilages

Answer 8

They have 2 major movements:

They swivel on an axis that runs straight down through the middle of the cartilages

• Can slide towards each other on the lamina of the cricoid cartilation (contributes to closing the vocal ligaments)
• Can slide away from each other

Question 9

Where is the epiglottic cartilage, what is the major function?

Answer 9

It projects/originates from posterior aspect of the angle of the cricoid cartilage (anteriorly) and fans out to a top projection that sits behind posterior third of the tongue and hyoid bone.

It is very important as the tongue and food bolus physically push the epiglottis down during swallowing to project laryngeal inlet

Question 10

Where do the vocal ligaments arise and attach to?

Answer 10

They run from the tips of the two vocal processes of the arytenoid cartilages posteriorly and project anteriorly through the midline towards the posterior aspect of the angle of the thyroid cartilage.

Question 11

Describe the formation of the vestibular (false) and vocal (true) cords

Answer 11

A mucosa lines the epiglottis and it runs down on the internal wall of the lamina of the thyroid cartilage.

It hits a membrane along the path (don’t need to know this membrane) and produces a vestibular fold just above the vocal ligament and that projects outwards toward the thyroid cartilage

The mucosa then runs down the thyroid cartilage and then folds back up over the top of the vocal ligament forming the vocal cords and then continues down in the airways

Question 12

How is the vestibular fold involved in phonation?

Answer 12

It is not

It lies superior to the true sound producing vocal cords and helps to close the glottis during swallowing

Question 13

What position to the vocal cords need to be in, in order to produce phonation?

Answer 13

Vocal ligaments need to be adducted for phonation and abducted for breathing

When they are adducted towards each other in the midline they push against each other and vibrate to create the sound

Question 14

How are various different types of sounds produced if there is only the adduction/abduction swivel action of the arytenoid cartilages?

Answer 14

The various sounds are altered by related structures like the mouth and oral cavity, nasal cavity and muscles.

Question 15

What causes the arytenoid cartilages to move and thus what causes the vocal cords to move?

Answer 15

Movement of the ligaments and alteration of the postition of the vocal cords in and out requires the intrinsic muscles of the larynx to have action mostly on the arytenoid cartilages and on other muscles to produce movement of the vocal ligaments

Question 16

What are the major intrinsic muscles of the larynx?

Answer 16

1. Posterior cricoarytenoid
2. Lateral cricoarytenoid
3. Transverse and oblique arytenoids
4. Cricothyroid
5. Vocalis

Question 17

What are the intrinsic muscles of the larynx that are involved in abduction of the vocal cords? (ie. breathing)

Answer 17

Posterior cricoarytenoid

Damage to this muscle is determinental as it is the only muscle that is responsible for opening the tube to air flow

Question 18

What are the intrinsic muscles of the larynx that are involved in adduction of the vocal cords? (ie. basic phonation)

Answer 18

The Lateral cricoarytenoid muscle

Question 19

Describe the role of the cricothyroid muscle

Answer 19

Attaches to the inside lamina of the thyroid cartilage.

It pulls the back end of thyroid cartilage forward (angle moves forward) stretching ligaments causing higher frequency fibration = higher pitched sounds

Question 20

Describe the role of the cricothyroid and Vocalis muscles

Answer 20

Shortens the vocal ligament (loose) and vibrate with lower frequency

Question 21

What are the 2 main nerves that supply the intrinsic muscles of the larynx?

Answer 21

All of the intrinsic muscles are ultimately all supplied by branches of the vagus nerve.

Except for the cricothyroid muscle (which is innervated by a branch of the superior laryngeal nerve: from external laryngeal nerve)

Question 22

What is the major branch of the vagus nerve that supplies the majority of the intrinsic muscles of the larynx?

Answer 22

The recurrent laryngeal nerves that are given off from the vagus nerve (left hooking around the ligamentum arteriosum and the right hooking under the subclavian artery)

Question 23

What happens to motor innervation of the muscles when there is damage to the recurrent laryngeal nerve?

Answer 23

Causes problems adduction and abduction so ligament is immobilised and can’t move to midline

• Ligaments can’t vibrate against each other = hoarse voice (inappropriate vibration)
• Stridor caused by the effort in producing sound due to large energy to cause vocal ligament to flap

Question 24

What happens when there is damage to the external laryngeal nerve (which supplies the cricothyroid muscle)?

Answer 24

Difficulty with production of high pitch sounds as the muscle isn’t able to pull the vocal cords and lengthen them. The patient will still be able to produce sound and breath

Question 25

What nerves supply the sensory innervation to the mucosa of the larynx? What are the important reflexes that these nerves are involved in?

Answer 25

Inferior laryngeal and the Inferior laryngeal, which are still branches off the recurrent laryngeal nerve They provide the sensory to mucosa below the vocal ligament. They are important for **coughing and gag reflex**

Question 26

The larynx is a very vascular region. Describe the blood supply

Answer 26

Blood supply comes from thyroid vessels above and thyroid vessels from below supplying blood to the thyroid gland (on top of the trachea) and gives off little branches going to the larynx itself

Question 27

What is the difference between a tracheotomy and a cricothyroid membrane puncture. What are the considerations of doing the two?

Answer 27

## Footnote A tracheotomy is cutting into the trachea. You need to cut through the inferior thyroid vessels in the area of the trachea for a tracheotomy. Cutting of the vessels causes bleeding directly into the airways (drowns the person). However if it is not an emergency situation, it is a bigger area and good access. Cricothyroid membrane is the area where there isn’t a lot of vasculature in the midline below the level of the vocal ligaments. So it is a good place to go in emergencies

Question 28

Consider path of intubation tube for artificial ventilation

Answer 28

Question 29

What is the area behind the larynx?

Answer 29

The laryngopharynx

Question 30

The epiglottis doesn’t form a perfect seal around the larynx. What helps to compensate for this?

Answer 30

The **larynx moves up** as you swallow (meeting the epiglottis above forming the tight seal)

Question 31

Fluids don’t normally go through the larynx through the main tube. Why is this and how does the fluid enter the oesophagus?

Answer 31

Fluids don’t have the weight to push the epiglottis, so they drain into the **piriform recess** which are little grooves (channels) out and around epiglottis

Question 32

What are the main components of the laryngopharynx? Label the following diagram:

Answer 32

Question 33

Describe the sensory innervation to the pharynx

Answer 33

The entire pharynx is mainly supplied by pharyngeal branches coming of the glossopharyngeal nerve (CN IX). This innervation is reinforced by some branches of the trigeminal nerve (pharyngeal branches of the maxillary nerve) superiorly and the branches of the vagus nerve inferiorly – internal laryngeal nerve (mucosa above the vocal ligaments)

Question 34

Give examples of referred pain from different parts of the larynx to different parts of the face (nerve distribution)

Answer 34

Eg. The middle ear mucosa also innervated by the glossopharyngeal nerve. Middle ear infections can have pain referring to the palatine tonsils in the oropharynx

Question 35

What is the major motor nerve supply to the pharynx?

Answer 35

* Mostly from pharyngeal branches of Vagus (CN X) * Except for Stylopharyngeus muscle which is supplied by CN IX

Question 36

What are the pharyngeal branches of the vagus nerve responsible for in terms of important reflexes?

Answer 36

Swallowing and Efferent arc of gag reflex

Question 37

Describe the steps in the deglutition (swallowing) process [8 steps]

Answer 37

1. Bolus shaped and pushed by tongue to palate. 2. Soft palate descends and palatal arches are approximated to grip and push the bolus into the oropharynx. 3. Soft palate elevated and tightened to prevent bolus entering nasal cavity. 4. Larynx and pharynx elevated to bring bolus closer to oesophagus. 5. Laryngeal inlet closed to prevent bolus from entering the trachea. 6. Bolus is pushed down the oropharynx and over the epiglottis. 7. Bolus forced down through laryngopharynx and into oesophagus. 8. Larynx depressed to return to normal position (mainly by elastic recoil).