The Larynx

Question 1

What are common clinical conditions of the larynx?

Answer 1

Infection, inflammation and neoplasms

Question 2

What is at risk during thyroid surgery?

Answer 2

The laryngeal nerves

Question 3

What is a cricothyroidotomy and when may it be required?

Answer 3

It is a procedure to give emergency access to the larynx, and may be performed if there is acute airway obstruction.

Question 4

Which structures are easily palpable?

Answer 4

The hyoid, the laryngeal prominence and the cricoid cartilage.

Question 5

Which structures are important in an emergency cricothyroidotomy?

Answer 5

The cricoid cartilage with the cricothyroid membrane above it - this is the membrane that will be punctured in the procedure.

Question 6

What are the 3 basic functions of the larynx?

Answer 6

1) provision of an airway and protection of that airway
2) effort closure in coughing sneezing and abdominal straining
3) phonation, a complex process involving all the intrinsic muscles of the larynx

Question 7

What are common clinical conditions affecting laryngeal function?

Answer 7

Laryngitis - inflammation of the vocal folds leading to hoarseness or aphonia
Vocal cord nodules - due to overuse of the vocal cords
Carcinoma - mainly squamous cell, occurring especially often in smokers.

Question 8

What is the thyroid angle in adult males compared to adult females?

Answer 8

Roughly 90 degrees in men, roughly 120 degrees in women.

Question 9

What causes the change in pitch of voice in adult men?

Answer 9

Mainly the increased mass and structure of the vocal folds, also the fact that the length of the vocal cords is nearly doubled.

Question 10

What are the 2 groups of extrinsic muscles?

Answer 10

Elevators of the larynx and depressors of the larynx.

Question 11

Name the elevators of the larynx that act via the hyoid.

Answer 11

Mylohyoid, stylohyoid, geniohyoid, digastric

Question 12

Name the elevators of the larynx that act directly.

Answer 12

Stylopharyngeus, palatopharyngeus, salpingopharyngeus

Question 13

Name the depressors of the larynx that act via the hyoid.

Answer 13

Sternohyoid, omohyoid, thyrohyoid.

Question 14

Name the depressor of the larynx that acts directly.

Answer 14

Sternothyroid

Question 15

How is the larynx normally returned to its rest position?

Answer 15

The elevated larynx is normally returned to its rest position by elastic recoil of the trachea.

Question 16

When does active depression of the larynx occur?

Answer 16

During deep inspiration and to increase the capacity of the resonating chambers during low frequency phonation.

Question 17

Where do neovascular structures get into the larynx above the vocal folds?

Answer 17

They pierce the thyrohyoid membrane.

Question 18

Where do neovascular structures get into the larynx below the vocal folds?

Answer 18

They enter or leave beneath the inferior constrictor of the pharynx.

Question 19

What is the blood supply of the larynx to the vocal folds and above?

Answer 19

The superior laryngeal branch of the superior thyroid artery (from the external carotid artery)

Question 20

What is the blood supply of the larynx below the vocal folds?

Answer 20

The interior laryngeal branch of the inferior thyroid artery (from the subclavian artery)

Question 21

What is the venous drainage of the larynx to the vocal folds and above?

Answer 21

The superior laryngeal veins which drain into the superior thyroid veins (then into the internal jugular vein)

Question 22

What is the venous drainage of the larynx below the vocal folds?

Answer 22

The inferior laryngeal veins which drain into the inferior thyroid veins (then into the brachiocephalic vein, mainly the left one)

Question 23

What are the lymphatics of the larynx to the vocal cords and above?

Answer 23

The anterosuperior group of deep cervical lymph nodes.

Question 24

What are the lymphatics of the larynx below the vocal cords?

Answer 24

The posteroinferior group of deep cervical lymph nodes

Question 25

What is the nervous supply to the mucosa of the vocal folds and above?

Answer 25

The internal branch of the superior laryngeal nerve of the vagus.

Question 26

What is the nervous supply to the mucosa below the vocal folds?

Answer 26

The recurrent laryngeal nerve of the vagus.

Question 27

What is the sympathetic supply to the vocal folds and above?

Answer 27

Fibres travelling with the superior laryngeal artery from the superior cervical ganglion.

Question 28

What is the sympathetic supply to below the vocal folds?

Answer 28

Fibres travelling with the inferior laryngeal artery from the middle cervical ganglion.

Question 29

What happens in unilateral recurrent laryngeal nerve injury?

Answer 29

The affected cord is semi-abducted and the other cord crosses the midline to compensate, leading to minimal defects in phonation.

Question 30

What happens in bilateral recurrent laryngeal nerve damage?

Answer 30

Both cords are semi-abducted, leading to difficulties in protecting the glottis, phonation and coughing. Emergency cricothyroidotomy or tracheostomy may be required.

Question 31

What happens in damage to the external branch of the superior laryngeal nerve?

Answer 31

(It supplies the cricothyroid)

Problems with phonation, especially at high frequencies. If the internal branch is also injured, supraglottic sensation may be lost.

Question 32

What needs to be done during thyroid surgery?

Answer 32

Intraopertaive electrophysiological monitoring of both branches of the superior laryngeal nerve.

Question 33

What is the sequence of events during swallowing? (4)

Answer 33

1) Closure of the vestibular and vocal folds.
2) Closure of the laryngeal inlet by contraction of the aryepiglotticus.
3) Elevation of the larynx by the action of extrinsic muscles.
4) Protection of the laryngeal inlet by the epiglottis, which flaps down like a lid.

Question 34

Where does the bolus of food have to reach for the laryngeal inlet to re-open and respiration to resume?

Answer 34

The oesophagus

Question 35

Describe what happens in coughing.

Answer 35

The vocal folds are powerfully adducted. Compressed air explodes through the larynx when the cords are suddenly abducted.

Question 36

Describe what happens in abdominal straining.

Answer 36

The closed vocal folds prevent upwards displacement of the diaphragm, increasing intra-abdominal pressure.

Question 37

What causes the distinctive grunt during evacuation or heavy lifting?

Answer 37

The escape of compressed air caused by the diaphragm being forced up.