Page 371 - Anatomy and Physiology of Farm Animals, 8th Edition

356 / Anatomy and Physiology of Farm Animals

(A)
VetBooks.ir Arytenoid Rima glottidis

cartilages

Vocal cords
Epiglottis

Soft palate

(B)

Figure 19-6. Equine larynx as viewed with an endoscope. Notice the width of the rima glottidis at (A)
exhalation versus (B) a forceful inspiration. The increased diameter results from muscles rotating the
arytenoid cartilages which abducts the vocal folds. Source: endoscopic views courtesy of Dean
Hendrickson, Colorado State University, Colorado, USA.

Injury to one of the recurrent laryn- glottidis during forceful inspiration and
geal nerves will result in paralysis of consequently has difficulty bringing suf-
most of the laryngeal muscles on the ficient air into the lungs when exercis-
same side. Paralysis of the muscle that ing. The flaccid vocal ligament flutters
abducts the arytenoid cartilages and as air moves rapidly past it, generating a
thereby increases the diameter of the loud, hoarse sound. Roaring usually is
airway (the dorsal cricoarytenoid mus- due to degeneration of the left recurrent
cle) results in a condition in horses called laryngeal nerve, as this nerve’s course is
laryngeal hemiplegia or roaring. A horse somewhat longer than that of the right
that is a roarer cannot expand the rima recurrent laryngeal nerve.