15. Functional Anatomy Of The Larynx

Question 1

What are the boarders of the larynx?

Answer 1

From the laryngeal inlet to the trachea at C6/lower boarder of the cricoid cartilage.

Question 2

What route does inspired air take to the trachea?

Answer 2

Inspired air via oral cavity/nasopharynx.
Oropharynx.
Larynx.
Trachea.

Question 3

What route does food take to the oesophagus?

Answer 3

Food via oral cavity.
Oropharynx.
Laryngopharynx.
Oesophagus.

Question 4

What is the main function of the larynx?

Answer 4

To provide a protective sphincter for the lower respiratory tract.

Question 5

What 3 single cartilages and 1 paired cartilages form the framework of the larynx?

Answer 5

3 single:
Thyroid.
Cricoid.
Epiglottis.
Paired:
Arytenoid cartilages.
(There are 2 others don't need to know).

Question 6

What 4 membranes and ligaments connect the cartilages and the hyoid and help to give shape to the larynx?

Answer 6

Thyrohyoid membrane.
Cricothyroid ligament.
Cricotracheal membrane.
Quadrangular membrane.

Question 7

Via what membrane can access to the airway be gained in an emergency if the patient cannot be incubated or ventilated (eg swelling to vocal cords)?

Answer 7

Cricothyroid membrane.

Question 8

What forms the vestibular ligament (false vocal cord)?

Answer 8

Free lower border of the quadrangular membrane.

Question 9

What forms the vocal ligament?

Answer 9

Thickened edge of the upper free border of the cricothyroid ligament.

Question 10

What are the 3 regions of the larynx and what separates them?

Answer 10

Supraglottis.
Glottis.
Infraglottis.
Mucosal folds formed by ligaments/membranes and cartilages.

Question 11

What type of epithelium lines the larynx?

Answer 11

Pseudostratified ciliated columnar epithelium (is a component of the respiratory tract).

Question 12

What landmark can help you orientate yourself when looking at the epiglottis?

Answer 12

Point of rima glottis is anterior.

Question 13

What are the two broad functions of the laryngeal muscles?

Answer 13

Alter the size and shape of the inlet in breathing and swallowing.
Move position to alter tension in the vocal cords in phonation and coughing.

Question 14

What is the only muscle of all the intrinsic muscles of the larynx that abducts (opens) the vocal cords?

Answer 14

Posterior cricoarytenoid.

Question 15

What is the narrowest part of the larynx?

Answer 15

Glottis.

Question 16

What determines the position of the true vocal cords and therefore size of the rina glottis apeture?

Answer 16

Position of arytenoids on cricoid cartilage.

Question 17

What nerve supplies all of the laryngeal muscles except the cricothyroid muscle?

Answer 17

Recurrent laryngeal nerve of CN X vagus.

Question 18

How do the vocal cords move during inspiration and expiration?

Answer 18

Vocal cords abduct - glottis wide open.

Question 19

How do the vocal cords move during phonation?

Answer 19

Adduct - expired air is forced through closely adducted vocal cords to vibrate a column of air.

Question 20

How do the vocal cords move during a cough?

Answer 20

Powerfully adduct, intrathoracic pressure builds, then cords suddenly abduct.

Question 21

How can the pitch of vocal sound be altered?

Answer 21

Cricothyroid muscle alters the tension and length of true vocal cords - vocal cords taught for high-pitched sounds, cords relaxed for low-pitched sounds.

Question 22

What nerve innervates the cricothyroid muscle?

Answer 22

External branch of the superior laryngeal nerve of CN X vagus.

Question 23

What does injury of the external laryngeal nerve (which gives off the superior laryngeal artery) cause eg in thyroid surgery due to close proximity to the superior thyroid artery? And why?

Answer 23

Hoarseness of voice especially when attempting high pitched sounds. Innervates the cricothyroid muscle which alters tension in the vocal chords.

Question 24

How does the larynx close in swallowing to protect the airways?

Answer 24

Contraction of aryepiglottic muscles acts to narrow the laryngeal inlet and pull down the epiglottis, assisted by elevation of the larynx by the pharyngeal muscles and suprahyoid muscles pulling the larynx up and forward. This results in closure of the glottis.

Question 25

What is the function of the internal branch of the superior laryngeal nerve?

Answer 25

Sensory above the vocal cords.

Question 26

What nerve provides sensory innervation below the vocal cords?

Answer 26

Recurrent laryngeal nerve.

Question 27

What nerve has a close relationship with the inferior thyroid arteries supplying the thyroid gland?

Answer 27

Recurrent laryngeal nerve.

Question 28

Name 2 ways in which the recurrent laryngeal nerve can be injured? What type of palsy would each lead to?

Answer 28

Aortic arch aneurysm damaging the left RLN - unilateral vocal cord palsy.
Cancer involving the apex of the lung damaging the right RLN - unilateral vocal cord palsy.
Disease or surgery involving the larynx, oesophagus or thyroid - bilateral vocal cord palsy.

Question 29

What position does a paralysed vocal cord assume?

Answer 29

Paramedian position.

Question 30

What symptoms does a unilateral palsy lead to?

Answer 30

Hoarseness of voice with or without ineffective cough, as often the contralateral side compensates in time by crossing the midline to meet the vocal cord on the affected side.

Question 31

What symptoms does a bilateral vocal cord palsy lead to?

Answer 31

Both vocal cords in paramedian position, so narrow glottis resulting in significant airway obstruction and therefore stridor, distress, hypoxia, cyanosed, raised respiratory rate.

Question 32

Name 2 other conditions involving the larynx that can threaten the airway.

Answer 32

Croup.
Epiglottitis.
Laryngeal oedema eg in an allergic reaction.