The cricothyroid muscle is the only tensor muscle of the

larynx The larynx (), commonly called the voice box, is an organ (anatomy), organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal ...

aiding with

phonation The term phonation has slightly different meanings depending on the subfield of phonetics. Among some phoneticians, ''phonation'' is the process by which the vocal folds produce certain sounds through quasi-periodic vibration. This is the defi ...

. It is innervated by the superior laryngeal nerve. Its action tilts the thyroid forward to help tense the

vocal cords In humans, the vocal cords, also known as vocal folds, are folds of throat tissues that are key in creating sounds through Speech, vocalization. The length of the vocal cords affects the pitch of voice, similar to a violin string. Open when brea ...

, thus increasing the pitch of the voice.

Structure

The cricothyroid muscle is a fan-shaped muscle situated at the outer surface of the larynx.

Origin

The cricothyroid muscle originates from the anterolateral aspect of the cricoid cartilage.

Insertion

The cricothyroid muscle splits into two groups or parts. The oblique part travels posterolaterally and inserts onto the inferior cornu of the thyroid cartilage. The straight part travels posterosuperiorly and inserts onto the inferior margin of the lamina of the thyroid cartilage.

Innervation

The cricothyroid muscle is innervated by the external branch of the superior laryngeal nerve (a branch of the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

). It is the only muscle innervated by this nerve.

Function

The cricothyroid muscle produces tension and elongation of the

. They draw up the arch of the cricoid cartilage and tilt back the upper border of the cricoid cartilage lamina. The distance between the vocal processes and the angle of the thyroid is increased, elongating and thus tensing the vocal folds, thereby resulting in higher pitch

. They work as antagonists to the posterior cricoarytenoid muscles.

Clinical significance

The cricothyroid muscles may be injected with

botulinum toxin Botulinum toxin, or botulinum neurotoxin (commonly called botox), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon en ...

whilst treating spasmodic dysphonia. This is usually performed under guidance from

electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyo ...

Additional images

File:Gray560.png, The veins of the thyroid gland. File:Gray562.png, The fascia and middle thyroid veins. File:Gray957.png, Side view of the larynx, showing muscular attachments.

References

{{DEFAULTSORT:Cricothyroid Muscle Muscles of the head and neck