Vocalis muscle

Origin and insertion

The vocalis muscle is a small, strand like muscle that originates at the lateral surface of vocal process of arytenoid cartilage. It runs anteromedially across the laryngeal inlet and attaches to the anterior part of the ipsilateral vocal ligament near the thyroid cartilage. 

It is debated among anatomists whether this muscle is really a distinct muscle or part of the thyroarytenoid muscle due to their close relation. The latter suggests that the vocalis muscle is formed from its medial detached part, thyroarytenoid internus, consisting of more delicate muscle fibers than the thyroarytenoid muscle itself.

Relations

While extending from the arytenoid cartilage towards the thyroid cartilage, the vocalis muscle runs in parallel with the vocal ligament, up until it inserts on the ligament’s anterior part. The vocalis muscle, along with the vocal ligament and the thyroarytenoid muscle, forms the deepest structure of the mucous membrane covered vocal folds.

The space between the right and left vocal folds is called the rima glottidis; it leads into the larynx. Thus the rima glottidis is bound by the vocal cords laterally on each side, the thyroid cartilage anteriorly and the interarytenoid space posteriorly.

Innervation

Vocalis and thyroarytenoid muscles are innervated by the recurrent laryngeal nerve, a branch of the vagus nerve (CN X). They receive a communicating branch from the external laryngeal nerve as well, although the role of this nerve supply is not well understood.

Blood supply

The vocalis muscle receives its arterial supply from the laryngeal branches of the superior thyroid artery, the first branch of the external carotid artery; and the inferior thyroid artery, a branch of the thyrocervical trunk. Venous blood from vocalis is drained by the superior and inferior laryngeal veins, which are tributaries of the internal jugular vein. 

Function

The vocalis muscle makes small adjustments to the tension of the vocal ligaments. Similar to a rubber band, lengthening of the vocal folds also ‘thins’ them, while shortening of the vocal folds ‘thickens’ them. Thus the general action of vocalis is to shorten, and thicken, the vocal folds and thereby change the tonal quality of the voice.

Since the vocalis muscle attaches at the anterior part of the vocal ligament, its contraction can exhibit a tension of the anterior part, with simultaneous relaxation of the posterior part of the vocal cords.This action results in the production of a high-pitched voice.

Do you think you know everything about the vocal cords? Test yourself with the following learning materials and their integrated quizzes and see where you stand: