Cricothyroid Muscle in Respiration

Abstract

Although the phonatory activity of cricothyroid muscle is well-known, its respiratory role often remains unrecognized. Recent data suggest this muscle plays a major role in the overall regulation of breathing by its control of expiratory resistance and flow. Cricothyroid contraction in expiration results in vocal elongation increasing glottic size. Such a mechanical effect reduces airway resistance and shortens expiratory duration. By such a mechanism, the rate of respiration may ultimately be modified using the larynx as the principal effector of this control. In this regard, cricothyroid expiratory activity is a pressure-sensitive evoked response influenced by afferent vagal stimuli. Its activity is triggered by a critical threshold of pressure-increase with respect to time, and its duration is directly dependent on the duration of positive subglottic pressure. The threshold of cricothyroid activation is reduced in hypercapnia and elevated in hypocapnic states.

Laryngeal nerve activity during pulse emission in the CF-FM bat,Rhinolophus ferrumequinum

“…This finding coincides with the experimental results of Hast (1967), Suzuki and Kirchner (1969), Suzuki et al (1970) and Horiuchi and Sasaki (1978) who worked on other types of mammals. They showed that the m. cricoarytenoideus posterior is active during inhalation but not during expiration.…”

Comprehensive Review of Thyroid Embryology, Anatomy, Histology, and Physiology for Surgeons

“…The external branch of SLN supplies the cricothyroid muscle, which is the only tensor muscle of the vocal cords [37]. In addition to its contribution to phonation, the cricothyroid muscle plays a role in the overall regulation of breathing by its control of expiratory resistance and flow [53]. The nerve enters the cricothyroid muscle laterally on its deep surface.…”

The Human Cricothyroid Muscle: Three Muscle Bellies and Their Innervation Patterns

“…It is known that the human CT muscle is active during phonation 1-5 and respiration. [6][7][8][9][10] However, little is known about how its bellies work during both motor tasks. As neural control of a compartmentalized muscle is intimately bound up with muscle functions, 12,[15][16][17] separate nerve supply patterns of the CT bellies indicate that each of the bellies may activate independently and participate in specific upper airway motor tasks.…”

“…Thus, CT muscle action is integral to lengthening, tensing, and adducting the vocal folds which are critical for its functions during phonation [1][2][3][4][5] and respiration. [6][7][8][9][10] The human CT is traditionally described as consisting of two bellies: rectus and oblique. However, a third belly has been revealed in the canine CT muscle by Zaretsky and Sanders.…”