Chapter 101: Larynx

Question 1

Where do the cranial laryngeal nerves and arteries pass though?

Answer 1

Through the rostral thyroid notches.

Question 2

The extrinsic muscles of the larynx constrict the caudal part of the pharynx. Name them?

Answer 2

Cricopharyngeus and thyropharyngeus

Question 3

Where does cricoarytenoideus dorsalis insert?

Answer 3

On the muscular process of the arytenoid cartilage which is lateral to the cricoarytenoid articulation.

Question 4

Thyropharyngeus - function, insertion and innervation?

Answer 4

• Covers the outside of the larynx, extends from lateral surface of thyroid cartilage and inserts on the median raphe of dorsal pharynx
• innervated by glossopharyngeal and vagal nerves
• constrict caudal part of the pharynx

Question 5

Cricopharyngeus - function, insertion and innervation?

Answer 5

-caudal to the thyropharyngeus muscle - arising from the lateral surface of cricoid cartilage and inserting on medial raphe of pharynx
- on caudal margin some fibers blend with the esophagus
- innervated by glossopharyngeal and vagal nerves
- constrict caudal part of the pharynx

Question 6

What is the most important intrinsic muscle of the larynx?

Answer 6

Cricoarytenoideus dorsalis

Abducts the arytenoid cartilage to open the glottis.

Question 7

The intrinsic muscles are responsible for laryngeal function. What are the 6 intrinsic muscles of the larynx?

Answer 7

• CAD
• CAL
• Thyroarytenoideus
• Arytenoideus transversus
• Hyoepiglotticus
• Cricothyroideus

Question 8

What nerves innervate the larynx?

Answer 8

Cranial and caudal laryngeal nerves, which arise from the vagus.

The caudal laryngeal nerve is the terminal segment of the recurrent laryngeal nerve.

The cranial laryngeal has an internal branch that anastomoses with the caudal, and an external branch that is the afferent limb of the cough reflex.

Question 9

The caudal laryngeal nerve supplies all the intrinsic laryngeal muscles except for which muscle?

Answer 9

Cricothyroideus

Question 10

Which arteries are the primary blood supply to the larynx?

Answer 10

Cranial and caudal thyroid arteries.

Question 11

How does feline laryngeal anatomy differ from dogs?

Answer 11

• The arytenoid cartilages lack a cuneiform and corniculate process
• true aryepiglottic folds are absent
• vocal cords are thick and rounded
• ventricles are absent

Question 12

Name the (4) processes of the arytenoid cartilages:

Answer 12

• Cuneiform
• Corniculate
• Vocal
• Muscular

Question 13

What are three functions of the larynx?

Answer 13

Block laryngeal opening during swallowing
control airway resistance
voice production

Question 14

What are the three stages of laryngeal collapse?

Answer 14

• Stage I - Everted laryngeal saccules
• Stage II - Cuneiform process loses its rigidity and becomes medially displaced
• Stage III - Corniculate process collapse, resulting in loss of dorsal arch of rima glottidis

Question 15

What lymph nodes drain the larynx?

Answer 15

Medial retropharyngeal lymph nodes

Question 16

What is doxapram?

Answer 16

CNS stimulant which causes an increased respiratory rate and tidal volume. Used in laryngoscopy if respiration is weak/anesthesia too deep and need to verify normal function/lack thereof.

Question 17

Rapid narrowing and widening of the glottis by the laryngeal muscles and fast twitching of the diaphragm causes what in cats?

Answer 17

Purring (vibrations of respiratory air)

Question 18

Name the (6) cartilages of the larynx:

Answer 18

Epiglottic
Thyroid
Cricoid
Sesamoid
Interarytenoid
Arytenoid

Question 19

Pathway of the left caudal laryngeal nerve?

Answer 19

The left recurrent laryngeal nerve from the left vagus arches around the aorta, ascends along the trachea, and gives off the pararecurrent laryngeal nerve before terminating as the left caudal laryngeal nerve.