Page 101 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 7
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Surgery of the larynx

Michael B. Mison and Gert ter Haar

Anatomy abduction of the arytenoid cartilages as they rotate
caudolaterally around the crico arytenoid articulation. The
The larynx is a fibroelastic membranous tube in which glottis can also close very tightly when required (e.g.
several stiff hyaline cartilages are embedded to maintain a swallowing, laryngospasm) by the opposite rotation of
patent airway. It separates the upper and lower airways and the arytenoids caused by the cricoarytenoid lateralis,
acts as a valve during swallowing. It maintains a patent air- thyroarytenoid and transverse arytenoid muscles, which
way whilst supporting two sets of valves, the passive, results in adduction of the arytenoids and closure of the
hinged epiglottis and the more refined, active glottis. There vocal cords. The extrinsic muscles of the larynx suspend
are five main cartilaginous structures (Figure 7.1): the larynx from the hyoid apparatus (Figure 7.3) and
work to control the arytenoid cartilages.
• Cricoid cartilage
• Thyroid cartilage
• Paired arytenoid cartilages (with cuneiform,
corniculate, muscular and vocal processes)
• Epiglottic cartilage Corniculate Rima glottidis
• Sesamoid cartilage/interarytenoid cartilage. process

The larynx is anchored cranially to the thyrohyoid
bone of the hyoid apparatus via a synovial joint with the Cuneiform
process
cranial cornu of the thyroid cartilage. Its caudal attach-
ment is from the cricoid to the trachea. The rima glottidis
is the diamond-shaped airway formed dorsally by the Vocal fold
arytenoid cartilages and ventrally by the vocal folds
(Figure 7.2). This is the narrowest part of the larynx, thus
its size (controlled by intrinsic laryngeal muscles) will
determine the rate at which air can be passed into and Vestibular fold
out of the lungs. The glottis can be widened by contrac- Epiglottic cartilage
tion of the cricoarytenoid dorsalis muscles, causing

7.2 Anatomy of the larynx as viewed during laryngoscopy.

Arytenoid
cartilage
Hyoid Cricoid cartilage Thyropharyngeus
apparatus Cricopharyngeus
Oesophagus
Hyopharyngeus

First tracheal
Epiglottic Thyroid ring
cartilage cartilage
Thyrohyoideus Sternohyoideus Sternothyroideus

7.1 The laryngeal cartilages. 7.3 Muscles surrounding the larynx.

92 BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, second edition. Edited by Daniel J. Brockman, David E. Holt and Gert ter Haar. ©BSAVA 2018

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