CorpusHuman Anatomy
RespiratoryMuscle group

Intrinsic laryngeal muscles

Musculi laryngis

Also known as: posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid, thyroarytenoid, vocalis, arytenoid muscles, transverse arytenoid

Small skeletal muscles connecting the laryngeal cartilages that open (abduct), close (adduct), tense and relax the vocal folds and constrict the laryngeal inlet.

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Overview

The intrinsic muscles act on the cricothyroid and cricoarytenoid joints. Abduction is achieved by a single muscle — the posterior cricoarytenoid — which is essential for breathing; adduction by the lateral cricoarytenoid, transverse and oblique arytenoids; tension (higher pitch) by cricothyroid, which tilts the thyroid cartilage forward on the cricoid; relaxation (lower pitch) by thyroarytenoid; and fine adjustment of fold stiffness by vocalis. The aryepiglottic and oblique arytenoid fibres act as a purse-string sphincter of the laryngeal inlet.

All are supplied by the recurrent laryngeal nerve except cricothyroid, supplied by the external laryngeal nerve. The extrinsic muscles (supra- and infrahyoid groups) instead move the larynx as a whole, elevating it in swallowing and depressing it afterwards.

Location

Within and around the laryngeal skeleton.

Parts & subdivisions

  1. Posterior cricoarytenoid
    Posterior surface of the cricoid lamina → muscular process of the arytenoid. Rotates the arytenoid laterally: the only abductor of the vocal folds ("safety muscle of the larynx"). RLN.
  2. Lateral cricoarytenoid
    Upper border of the cricoid arch → muscular process. Rotates the arytenoid medially: adducts the intermembranous glottis. RLN.
  3. Transverse and oblique arytenoids
    Between the two arytenoids; draw them together, closing the intercartilaginous glottis; oblique fibres continue as aryepiglottic muscles to narrow the inlet. RLN.
  4. Thyroarytenoid (and vocalis)
    Inner surface of the thyroid angle → anterolateral arytenoid. Draws the arytenoids forward, shortening and relaxing the folds (lowers pitch); vocalis (medial part) adjusts local tension. RLN.
  5. Cricothyroid
    Anterolateral cricoid arch → inferior border and inferior horn of the thyroid. Tilts the thyroid forward, lengthening and tensing the folds (raises pitch). External laryngeal nerve — the only intrinsic muscle not supplied by the RLN and the only one on the outside of the larynx.

Anatomy

Innervation

Recurrent laryngeal nerve (CN X; 6th arch) to all except cricothyroid; external branch of the superior laryngeal nerve (CN X; 4th arch) to cricothyroid. Nucleus ambiguus is the motor nucleus.

Arterial supply

Superior and inferior laryngeal arteries.

Function

  • Open the glottis for breathing.
  • Close the glottis and laryngeal inlet for airway protection and coughing.
  • Control pitch and quality of the voice.

Clinical significance

External laryngeal nerve injury

The nerve runs with the superior thyroid artery and can be injured when the artery is ligated at thyroidectomy: paralysis of cricothyroid causes a weak, monotonous voice unable to reach high notes — significant for singers.

Bilateral posterior cricoarytenoid paralysis

Without its only abductor the glottis cannot open, causing inspiratory stridor and potentially fatal obstruction.

Mnemonics

Abduct vs adduct

"PCA Pulls Cords Apart" — posterior cricoarytenoid abducts; "Lateral Lets them meet" — lateral cricoarytenoid adducts.

Test yourself

Which intrinsic laryngeal muscle is the only abductor of the vocal folds?
  1. Lateral cricoarytenoid
  2. Cricothyroid
  3. Transverse arytenoid
  4. Posterior cricoarytenoid

Answer: Posterior cricoarytenoid

The posterior cricoarytenoid rotates the arytenoid cartilages laterally, abducting the vocal processes and opening the rima glottidis. Bilateral paralysis (e.g. bilateral recurrent laryngeal nerve injury) leaves the folds near the midline and can cause life-threatening stridor.

More respiratory system questions

Compiled from standard anatomy and physiology references — see the Respiratory System sources. For education only; not medical advice.