How the Cricothyroid Muscle Controls Voice and Breathing

The cricothyroid is a small but remarkably important structure in the front of the neck, and the term actually refers to several related things at once: a muscle, a membrane, and a joint, all occupying the space between the cricoid and thyroid cartilages of the larynx. The cricothyroid muscle is the primary pitch-raising muscle of the human voice, while the cricothyroid membrane is the soft tissue emergency physicians target when they need to establish an airway fast. Understanding what the cricothyroid does, where it sits, and how it can go wrong touches on everything from singing to emergency medicine to gender-affirming surgery.

What the Cricothyroid Muscle Actually Does

The cricothyroid muscle runs between the two largest cartilages of the larynx: the thyroid cartilage (the structure behind your Adam’s apple) and the cricoid cartilage (a ring sitting just below it). When this muscle contracts, it tilts the thyroid cartilage forward relative to the cricoid, stretching and tensioning the vocal folds. Longer, tenser vocal folds vibrate at a higher frequency, so the net effect of cricothyroid contraction is a rise in pitch. Three-dimensional imaging during singing has confirmed this sequence: from a low note up to a moderate pitch, the primary movement is a backward tilt of the cricoid driven by the cricothyroid muscles, which stretches the vocal folds.

1PubMed. 3D analysis of the movements of the laryngeal cartilages during singing

The cricothyroid does not work alone, though. Inside the larynx, another muscle called the thyroarytenoid runs through the body of each vocal fold and acts as its main opponent. When the thyroarytenoid contracts, it shortens and thickens the vocal fold, lowering pitch. A computational study of this interplay found that while cricothyroid and thyroarytenoid activation both generally raised the fundamental frequency, moderate thyroarytenoid activation could actually produce a frequency drop under certain conditions.

2PubMed Central. A computational study of the influence of thyroarytenoid and cricothyroid muscle interaction on vocal fold dynamics in an MRI-based human laryngeal model

Vocal fold modeling work has shown a complementary finding: when the cricothyroid is strongly activated and the fold is already elongated, increasing thyroarytenoid contraction counteracts some of that stretch and lowers the fold’s natural vibration frequencies.

3PubMed Central. The influence of thyroarytenoid and cricothyroid muscle activation on vocal fold stiffness and eigenfrequencies

Pitch control, in other words, is not simply a matter of one muscle pulling harder. It is a tug-of-war between the cricothyroid stretching the fold from the outside and the thyroarytenoid stiffening or shortening it from the inside. Singers and trained speakers learn to balance these two forces with extraordinary precision, though they rarely think about it in those terms.

More Than One Belly

When anatomy textbooks describe the cricothyroid, they typically mention two parts: a vertical portion (the pars recta) and an angled portion (the pars obliqua). Dissection research has shown these two bellies differ in how much they raise pitch, rotate the cricothyroid joint, and translate the thyroid cartilage forward.

4PubMed. Functional differences between the two bellies of the cricothyroid muscle

A detailed cadaver study, however, identified three distinct bellies rather than two, adding a horizontal portion alongside the rectus and oblique parts. The nerve supply to each belly also varied. The external branch of the superior laryngeal nerve entered the muscle as a single trunk in about a third of specimens and as multiple branches in the rest. The rectus belly received three to seven nerve branches, while the oblique and horizontal bellies each received only one or two.

5PubMed. The human cricothyroid muscle: three muscle bellies and their innervation patterns

This variability matters clinically. If a surgeon needs to avoid the nerve during a thyroid operation, knowing that it may arrive as a single trunk or fan out into up to five branches changes the dissection strategy. And the fact that different bellies serve slightly different mechanical roles hints at why pitch control is so finely graded: the brain can independently dial up the contribution of each belly rather than simply turning the whole muscle on or off.

A Breathing Muscle Too

Most people associate the cricothyroid exclusively with voice, but it also plays a role in breathing. Studies using electromyography in awake, healthy volunteers found that the cricothyroid shows low-level rhythmic activity during quiet breathing, firing in phase with inspiration in most subjects. When breathing demands increased, through deep breathing, brief airway blockage, or elevated carbon dioxide levels, the cricothyroid ramped up further.

6PubMed. Respiratory activity of the cricothyroid muscle in conscious humans

A separate study measuring the timing of this inspiratory activity found that the cricothyroid began firing before airflow started, similar in pattern and timing to muscles that actively open the upper airway. The onset of its activity preceded airflow by roughly 170 milliseconds, and its firing pattern resembled that of a classic airway dilator rather than a pure voice muscle.

7PubMed. Respiratory-related activity of cricothyroid muscle in awake normal humans

The implication is that the cricothyroid helps stiffen or stabilize the airway during each breath, keeping it from collapsing inward as air rushes through. This dual role, serving both voice and respiration, is a reminder that laryngeal muscles rarely have just one job.

When Thyroid Surgery Puts the Nerve at Risk

The external branch of the superior laryngeal nerve, the sole motor supply to the cricothyroid muscle, runs dangerously close to the superior thyroid artery. During thyroid surgery, that artery must be tied off, and the nerve can be stretched, clamped, or cut in the process. Voice changes after thyroid operations are common and arise from multiple causes, but damage to this particular nerve produces a distinctive pattern: difficulty projecting, easy voice fatigue, and a narrowed pitch range, especially at the upper end.

8PubMed Central. Injury of the external branch of the superior laryngeal nerve in thyroid surgery

In one post-thyroidectomy study, electromyography documented a unilateral nerve injury in about 14 percent of patients who reported voice complaints, with easy voice fatigue and decreased pitch range being the most frequent symptoms.

9PubMed. Post-thyroidectomy superior laryngeal nerve injury

These injuries are notoriously underdiagnosed because they do not cause the obvious hoarseness associated with damage to the recurrent laryngeal nerve, which controls the vocal fold’s opening and closing muscles. A person whose cricothyroid is weakened on one side can still speak at conversational pitch and volume, so the problem might only surface when they try to sing, call across a room, or sustain their voice through a long workday.

Intraoperative nerve monitoring has become increasingly common as a way to reduce this risk. Direct stimulation of the nerve during surgery at a low current produces a measurable contraction of the cricothyroid, with response latencies recorded at roughly 1.4 milliseconds on each side, confirming that the nerve is intact before the surgeon proceeds.

10PubMed. Superior laryngeal nerve in thyroid surgery: anatomical identification and monitoring

The Impact on Vocal Fold Paralysis

When a person develops vocal fold paralysis, the recurrent laryngeal nerve is usually the one that has been damaged, leaving the fold unable to open or close properly. But if the superior laryngeal nerve is also injured, the cricothyroid loses its function too, and the voice outcome is measurably worse. A study comparing patients with recurrent nerve paralysis alone to those with combined recurrent and superior nerve paralysis found that the group with additional cricothyroid dysfunction had poorer vocal fold vibration and worse quality-of-life scores on both voice-specific and general health measures.

11PubMed. Cricothyroid muscle dysfunction impairs vocal fold vibration in unilateral vocal fold paralysis

Electromyography can help distinguish these two injury patterns. When patients with combined nerve damage attempted an upward pitch glide, the peak recruitment frequency of the cricothyroid was significantly lower, around 400 Hz, compared with roughly 780 Hz in patients whose superior laryngeal nerve was intact.

12PubMed. Quantitative laryngeal electromyography assessment of cricothyroid function in patients with unilateral vocal fold paralysis

For clinicians, this distinction guides treatment planning. A patient whose cricothyroid still works has better potential for voice recovery after medialization procedures, while one whose cricothyroid is also paralyzed may need additional interventions or adjusted expectations.

The Cricothyroid Membrane and Emergency Airway Access

Between the cricoid and thyroid cartilages, bridging the gap that the muscle does not cover, lies the cricothyroid membrane. Histological examination shows it to be a fibroelastic structure containing roughly equal proportions of collagen and elastic fibers.

13PubMed Central. Histology of the cricothyroid membrane: a clinical perspective

This membrane is the target for cricothyroidotomy, the emergency procedure in which a hole is made through the front of the neck to establish an airway when standard methods have failed. It sits close to the skin, has relatively little overlying vasculature, and provides a direct path into the tracheal lumen.

The challenge is finding it reliably under pressure. A study testing experienced anesthesiologists asked 18 clinicians to mark the puncture site on live subjects whose membrane boundaries had been mapped with ultrasound. Only about 30 percent of attempts landed over the membrane at all, and just 10 percent hit near its center.

14PubMed. Accuracy of surface landmark identification for cannula cricothyroidotomy

A systematic review of techniques to improve this accuracy found that ultrasound dramatically improved identification rates to near 100 percent once clinicians had some training, and that the skill could be learned in about an hour of structured practice with good retention at six months.

15British Journal of Anaesthesia. Airway ultrasonography for identifying the cricothyroid membrane: a systematic review of descriptive and comparative studies

In adolescents, the membrane is smaller, which complicates emergency access in younger patients. Measurements from CT scans showed that its height ranged from about 5.4 to 6.2 millimeters in male adolescents and 4.6 to 5.8 millimeters in female adolescents, with a strong association between membrane size and age.

16Pediatric Emergency Care. Anatomic Characteristics of the Adolescent Cricothyroid Membrane on Computed Tomography Scans

These small dimensions leave very little margin for error, which is one reason why surgical cricothyroidotomy in children remains a last resort.

Gender-Affirming Voice Surgery

The cricothyroid joint is the hinge that the cricothyroid muscle acts across, and surgeons have found a way to exploit this for pitch elevation. In cricothyroid approximation, the thyroid and cricoid cartilages are stitched closer together with permanent sutures, putting the vocal folds under constant tension. The effect mimics sustained cricothyroid muscle contraction, raising the resting pitch of the speaking voice.

17Operative Techniques in Otolaryngology-Head and Neck Surgery. Gender-affirming voice surgery: Pitch elevation

This procedure is one of the most studied options for transgender women seeking a higher speaking pitch. A case report involving a patient with a specific joint configuration showed that the mean speaking pitch rose from 134 Hz before any treatment to 150 Hz after voice therapy alone, then jumped to 184 Hz four weeks after cricothyroid approximation and climbed further to 199 Hz by six months. The pitch remained stable at roughly 203 to 209 Hz over five years of follow-up, and voice-related quality-of-life scores improved substantially.

18PubMed Central. Cricothyroid Approximation in Trans Women With Type A Cricothyroid Joints

Not every outcome is this favorable, however. Because the procedure works by mechanically shortening the distance between the two cartilages, it can fail if that distance is already naturally short. A report on unsuccessful cases analyzed with three-dimensional CT found that excessive pre-existing shortening of the cricothyroid gap left no room for the sutures to create additional tension.

19PubMed Central. Cricothyroid Approximation Surgery (Type IV Thyroplasty): Insights From Failure Cases and an Analysis of Contributing Factors Using Three-Dimensional Computed Tomography

Cricothyroid approximation also involves an external neck incision, which can produce a visible scar, and some literature notes a tendency for pitch to drift downward over the first one to two years as tissue relaxes around the sutures.

20Operative Techniques in Otolaryngology-Head and Neck Surgery. Gender-affirming voice surgery: Pitch elevation

For these reasons, another technique called anterior glottoplasty, which shortens the vibrating length of the vocal folds from the inside, has been gaining ground as an alternative.

The Cricothyroid Joint Itself

The cricothyroid joint is a small synovial joint on each side of the larynx where the inferior horn of the thyroid cartilage meets the cricoid. Its freedom of movement varies considerably between individuals. Some people have joints that allow a wide rocking motion, while others have joints that are stiffer or oriented differently, which affects how efficiently the cricothyroid muscle can stretch the vocal folds.

Because of this variability, the joint occasionally dislocates. Laryngeal trauma from a blow to the neck is the most common cause, though spontaneous dislocation without external force has been reported.

21PubMed. A rare case of spontaneous cricothyroid joint dislocation

Dislocation typically produces sudden voice change and pain, and diagnosis can be tricky because the joint is too small to see well on plain X-rays. CT imaging or direct laryngoscopy is usually needed to confirm it.

Pitch, Cartilage, and Aging

As people age, the cartilages of the larynx gradually stiffen and calcify, reducing the flexibility of the cricothyroid joint and altering how the vocal folds respond to muscle contraction. Research on professional singers using imaging found that the amount of thyroid cartilage deformation during pitch changes correlated strongly with age, with older singers showing less deformation.

22Elsevier / Journal of Voice. How Age and Frequency Impact the Thyroid Cartilages of Professional Singers

Pitch elevation also involves vertical movements of the entire laryngeal framework, not just the cricothyroid tilt. One study measuring the dynamics of these movements found that the vertical positions of the hyoid bone, cricoid, and thyroid cartilages had a stronger relationship to pitch change than the cricothyroid distance alone.

23PubMed. The effects of dynamic laryngeal movements on pitch control

This helps explain why aging voices lose range at the top end: it is not just that the cricothyroid muscle weakens, but that the cartilage it pulls on becomes less willing to move.

The Cricothyroid in Laryngeal Dystonia

Laryngeal dystonia, sometimes called spasmodic dysphonia, involves involuntary spasms of the laryngeal muscles that disrupt speech. In the adductor form, the vocal folds slam together, producing a strained, strangled quality. In the rarer abductor form, the folds fly apart, causing breathy voice breaks. Botulinum toxin injection into the overactive muscles is the standard treatment. For adductor dystonia, the toxin typically goes into the thyroarytenoid muscles. In some patients with abductor dystonia, however, the cricothyroid muscles were also injected, reflecting the muscle’s role in contributing to the abnormal vocal fold movement patterns.

24PubMed. Abductor laryngeal dystonia: a series treated with botulinum toxin

Superfast Cricothyroid Muscles in Bats

Humans push the cricothyroid to impressive speeds during rapid speech and singing, but echolocating bats operate on an entirely different level. As a bat closes in on prey during a terminal buzz, it may produce echolocation calls at rates exceeding 160 per second. Research has shown that previously unknown superfast muscles in the bat larynx, including the cricothyroid, power these extraordinary call rates, and that the maximum speed of the laryngeal muscles, not acoustic overlap between calls and returning echoes, is what limits how fast a bat can call.

25PubMed. Superfast muscles set maximum call rate in echolocating bats

What makes these muscles so fast? Electron microscopy of the bat cricothyroid revealed an extraordinarily well-developed sarcoplasmic reticulum, the internal membrane system that handles calcium cycling during muscle contraction. Faster calcium release and reuptake means the muscle can contract and relax in rapid succession, and the bat cricothyroid has far more of this machinery than a typical skeletal muscle.

26PubMed Central. The sarcoplasmic reticulum of the bat cricothroid muscle

Superfast muscles are rare among vertebrates, and wherever they appear, they seem to be driven by the demands of acoustic communication or sound production, whether in bats, some songbirds, or the swim bladder muscles of certain fish. The bat cricothyroid is one of the most extreme examples of evolutionary specialization of a muscle that, in humans, does its work at a comparatively leisurely pace.