cricothyroid
Summary
The cricothyroid muscle is the only tensor muscle of the larynx, responsible for elongating and tensing the vocal cords to increase pitch. It is innervated by the external branch of the superior laryngeal nerve, distinguishing it from all other intrinsic laryngeal muscles innervated by the recurrent laryngeal nerve. The cricothyroid membrane, located between the cricoid and thyroid cartilages, is the critical anatomic landmark for emergency airway access (cricothyrotomy).
Detail
The cricothyroid muscle originates from the anterolateral cricoid cartilage and inserts onto the inferior border and inferior horn of the thyroid cartilage. Contraction tilts the thyroid cartilage forward relative to the cricoid, increasing the distance between the thyroid and arytenoid cartilages, which stretches and tenses the vocal folds, raising pitch. This is why it is often called the 'pitch muscle.'
Clinically, the cricothyroid muscle is unique among intrinsic laryngeal muscles because it receives motor innervation from the external (motor) branch of the superior laryngeal nerve, a branch of the vagus nerve (CN X). All other intrinsic laryngeal muscles (posterior cricoarytenoid, lateral cricoarytenoid, transverse and oblique arytenoids, thyroarytenoid, vocalis) are innervated by the recurrent laryngeal nerve. Damage to the external laryngeal nerve (e.g., during thyroidectomy, since it runs close to the superior thyroid artery) causes weakened, monotone voice with reduced pitch range but does not cause airway compromise, unlike recurrent laryngeal nerve injury which can cause vocal cord paralysis and stridor.
The cricothyroid membrane (also called the conus elasticus) spans between the cricoid cartilage inferiorly and the thyroid cartilage superiorly, and is palpable in the midline of the neck as a soft depression below the laryngeal prominence (Adam's apple). This membrane is the site for emergency cricothyrotomy, performed when standard endotracheal intubation fails or is contraindicated (e.g., in severe facial trauma, upper airway obstruction, or anaphylaxis with laryngeal edema). It is preferred over tracheostomy in emergencies because it is more superficial, avoids the thyroid isthmus, and has fewer vascular structures nearby, making it faster and lower risk for rapid airway access.
High-yield board associations: Superior laryngeal nerve (external branch) = cricothyroid = pitch; Recurrent laryngeal nerve = all other intrinsic muscles = voice box protection/abduction-adduction of cords. Cricothyrotomy landmark = cricothyroid membrane.
Sources
- Moore's Clinically Oriented Anatomy
- Gray's Anatomy for Students
- First Aid for the USMLE Step 1
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.