TBL27 - Larynx

Question 1

What are the hyaline cartilaginous skeleton and associated skeletal muscles of the larynx derived from?

Answer 1

The hyaline cartilaginous skeleton and associated skeletal muscles of the larynx are derived from mesoderm of the 4th and 6th pharyngeal arches

Question 2

What does the thyrohyoid membrane connect to the hyoid bone and what does this facilitate? Name the ligament that connects the thyroid and cricoid cartilages.

Answer 2

1) The thyrohyoid membrane connects the large thyroid cartilage to the hyoid bone thereby facilitating movement of the larynx by the suprahyoid and infrahyoid muscles
2) The median cricothyroid ligament connects the thyroid and cricoid cartilages

Question 3

What forms the laryngeal prominence “Adam’s apple”? Where are the laminae of the thyroid cartilage separated?

Answer 3

1) The two large, plate-like laminae of the thyroid cartilage fuse in the anterior midline to form the laryngeal prominence “Adam’s apple”
2) The laminae of the thyroid cartilage are separated posteriorly

Question 4

Between the separated laminae, what do the paired arytenoid cartilages articulate with and why are these structures unlike the thyroid cartilage?

Answer 4

Between the separated laminae, the paired arytenoid cartilages articulate with the superior border of the cricoid cartilage that unlike the thyroid cartilage, completely encircles the laryngeal airway

Question 5

Where do the elastic vocal ligaments (cords) extend from and to? What is designated as the glottis?

Answer 5

1) The elastic vocal ligaments (cords) extend from the paired arytenoid cartilages to the midline junction of the thyroid cartilage laminae
2) The intervening aperture between the vocal cords is designated the glottis

Question 6

What does the tapered inferior end of the epiglottic cartilage attach to? In addition to the meshwork of type II collagen fibers, what does the matrix of the epiglottic cartilage contain? How does the epiglottic cartilage therefore compare to the hyaline cartilage?

Answer 6

1) The tapered inferior end of the epiglottic cartilage attaches to the midline junction of the thyroid cartilage laminae
2) In addition to the meshwork of type II collagen fibers, the matrix of the epiglottic cartilage contains elastic fibers; thus, the cartilage has more flexibility than hyaline cartilage and is designated elastic cartilage

Question 7

How does elastic cartilage contribute to epiglottic function during swallowing?

Answer 7

1) At rest, the epiglottis is usually upright and allows air to pass into the larynx and the rest of the lower respiratory airways
2) During swallowing, it folds back like a flap to cover the entrance to the larynx, to prevent food and liquid from entering the trachea

Question 8

What is the epiglottis immediately posterior to and what does it form the anterior wall of? What form the lateral and posterior walls of the inlet?

Answer 8

1) The epiglottis is immediately posterior to the root of the tongue and forms the anterior wall of the laryngeal inlet
2) The bilateral ary-epiglottic folds form the lateral and posterior walls of the inlet

Question 9

What are the ary-epiglottic folds created by and where do these structures extend from and to? What else join these structures that make up the ary-epiglottic folds?

Answer 9

1) The ary-epiglottic folds are created by the mucosa covered ary-epiglottic ligaments that extend from the arytenoid cartilages to the epiglottic cartilage
2) Ary-epiglottic muscles join the ligaments in the mucosa of the ary-epiglottic folds

Question 10

What does the epiglottis form the anterior wall of? Describe the core of the epiglottis.

Answer 10

1) The epiglottis forms the anterior wall of the laryngeal inlet
2) The core of the epiglottis is an elastic cartilaginous core

Question 11

What is the laryngeal vestibule? What is the infraglottic cavity?

Answer 11

1) The laryngeal vestibule is the luminal space between the laryngeal inlet and the vocal cords
2) The infraglottic cavity is the luminal space between the vocal cords and the trachea

Question 12

What is the width of the glottis regulated by during respiration and speaking?

Answer 12

During respiration and speaking, the width of the glottis is regulated by the laryngeal muscles

Question 13

After branching from CN X, what does the superior laryngeal nerve bifurcate into? Define the somatic sensory distribution of the internal laryngeal nerve and the somatic motor function of the external laryngeal nerve.

Answer 13

1) After branching from CN X, the superior laryngeal nerve bifurcates into the internal and external laryngeal nerves
2) The internal laryngeal nerve supplies sensory fibers to the laryngeal mucous membrane of the laryngeal vestibule and middle laryngeal cavity, including the superior surface of the vocal folds
3) At first, the external laryngeal nerve lies on the inferior pharyngeal constrictor; it then pierces the muscle, contributing to its innervation (with the pharyngeal plexus), and continues to supply the cricothyroid muscle

Question 14

Where does the recurrent laryngeal nerve arise from in the superior mediastinum? Where does this nerve course along, what does it terminate as and where, and what does this terminal branch provide somatic motor innervation to? Define the somatic sensory distribution of the inferior laryngeal nerve.

Answer 14

1) The recurrent laryngeal nerve arises from CN X in the superior mediastinum
2) It courses along the trachea to the larynx where it terminates as the inferior laryngeal nerve that provides somatic motor fibers to the laryngeal muscles
3) The inferior laryngeal nerve provides sensory fibers to the mucosa of the infraglottic cavity

Question 15

Why can removal of a swallowed object lodged in a piriform recess lead to the loss of sensation in the mucosa of the laryngeal vestibule?

Answer 15

1) The superior laryngeal nerve and its internal laryngeal branch are also vulnerable to injury during removal of the object if the instrument used to remove the foreign body accidentally pierces the mucous membrane
2) Injury to these nerves may result in anesthesia of the laryngeal mucous membrane as far inferiorly as the vocal folds

Question 16

How does the Heimlich maneuver remove foreign bodies aspirated into the laryngeal vestibule? Why can such aspiration be fatal and in extreme cases, what would permit rapid entry of air into the larynx?

Answer 16

1) Because the lungs still contain air, sudden compression of the abdomen (Heimlich maneuver) causes the diaphragm to elevate and compress the lungs, expelling air from the trachea into the larynx. This maneuver usually dislodges the food or other material from the larynx
2) Asphyxiation occurs, and the person will die in approximately 5 min from lack of oxygen if the obstruction is not removed
3) In extreme cases, experienced persons (e.g., physicians) insert a large-bore needle through the cricothyroid ligament (needle cricothyrotomy, or “coniotomy”) to permit fast entry of air

Question 17

What are the laryngeal arteries branches of? What do the superior laryngeal artery and internal laryngeal nerve pierce to enter the larynx?

Answer 17

1) The laryngeal arteries are branches of the superior and inferior thyroid arteries
2) The superior laryngeal artery and internal laryngeal nerve pierce the thyrohyoid membrane to enter the larynx

Question 18

Where does the inferior laryngeal artery course with along the trachea to the larynx?

Answer 18

The inferior laryngeal artery courses with the inferior laryngeal nerve along the trachea to the larynx

Question 19

Define the respective laryngeal muscles that adduct and abduct the vocal cords. Define those muscles that tense and relax the cords.

Answer 19

1) a) Posterior crico-arytenoid: Abducts vocal folds
b) Lateral cricoarytenoid: Adducts vocal folds (interligamentous portion)
c) Transverse and oblique arytenoids: Adduct arytenoid cartilages (adducting intercartilaginous portion of vocal folds, closing posterior rima glottidis)
2) a) Cricothyroid: Stretches and tenses vocal ligament
b) Thyro-arytenoid: Relaxes vocal ligament
c) Vocalis: Relaxes posterior vocal ligament while maintaining (or increasing) tension of anterior part

Question 20

Which laryngeal muscles are active during normal respiration, forced respiration, phonation, and whispering?

Answer 20

1) During normal respiration, the laryngeal muscles are relaxed
2) During a deep inhalation, the vocal ligaments are abducted by contraction of the posterior crico-arytenoid muscles
3) During phonation, the arytenoid muscles adduct the arytenoid cartilages at the same time that the lateral crico-arytenoid muscles moderately adduct
4) During whispering, the vocal ligaments are strongly adducted by the lateral crico-arytenoid muscles, but the relaxed arytenoid muscles allow air to pass between the arytenoid cartilages

Question 21

Why does a weak or hoarse voice result from unilateral recurrent laryngeal nerve injury and stridor result from bilateral nerve injury? How does injury to the external laryngeal nerve affect the voice?

Answer 21

1) In progressive lesions of the recurrent laryngeal nerve, abduction of the vocal ligaments is lost before adduction; conversely, during recovery, adduction returns before abduction. Hoarseness is the common symptom of serious disorders of the larynx, such as carcinoma of the vocal folds
2) When bilateral paralysis of the vocal folds occurs, the voice is almost absent because the vocal folds are motionless in a position that is slightly narrower than the usually neutral respiratory position. They cannot be adducted for phonation, nor can they be abducted for increased respiration, resulting in stridor (high pitched, noisy respiration)
3) Injury to the external branch of the superior laryngeal nerve results in a voice that is monotonous in character because the paralyzed cricothyroid muscle supplied by it is unable to vary the length and tension of the vocal fold

Question 22

What is the most common symptom of esophageal cancer and why can the cancer cause hoarseness?

Answer 22

1) The most common presenting complaint of esophageal cancer is dysphagia (difficulty in swallowing)
2) Compression of the recurrent laryngeal nerves by an esophageal tumor produces hoarseness

Question 23

Which muscles reflexively contract to close the laryngeal inlet? What is the stimulus for the reflexive contraction and when is the reflex diminished?

Answer 23

1) Contraction of the lateral crico-arytenoids, transverse and oblique arytenoids, and ary-epiglottic muscles brings the ary-epiglottic folds together and pulls the arytenoid cartilages toward the epiglottis
2) This action occurs reflexively in response to the presence of liquid or particles approaching or within the laryngeal vestibule
3) It is perhaps our strongest reflex, diminishing only after loss of consciousness, as in drowning