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Larynx

Last updated: September 23, 2021

Summarytoggle arrow icon

The larynx is a cartilaginous tube that connects the pharynx and the trachea. It is involved in producing sound, preventing aspiration, swallowing, breathing, and the cough reflex. It is composed of several cartilages (e.g., cricoid, thyroid, arytenoid) connected by ligaments, muscles (intrinsic and extrinsic), and membranes. The intrinsic muscles produce the fine movements necessary for sound production and breathing. The laryngeal cavity is divided into three parts: the supraglottis (contains the false vocal cords), glottis (contains the true vocal cord), and subglottis. The laryngeal cavity is lined by pseudostratified ciliated columnar epithelium, except for the true vocal cords (area of physiological stress), which are lined by stratified squamous epithelium. Smoking increases the risk of metaplasia in the transition zone between these two epithelial linings, which can progress to squamous cell carcinoma of the larynx. The larynx is supplied by the superior and inferior laryngeal arteries and drains into the superior and inferior laryngeal veins. It is innervated by the superior laryngeal nerve and recurrent laryngeal nerve. The recurrent laryngeal nerve is at particular risk of injury during thyroidectomy.

Overview

Function

Regions of the laryngeal cavity

Cartilages

  • Unpaired:
  • Paired:

Ligaments and joints

The cricothyroid ligament is where the incision is made for a cricothyrotomy.

The cricoarytenoid joint allows the vocal ligaments to be abducted and adducted.

Musculature

Extrinsic muscles

The extrinsic muscles connect the thyroid, cricoid, and arytenoid cartilage to other structures of the head and neck.

Function Extrinsic muscle
Elevation of larynx
Depression of larynx

Intrinsic muscles

The intrinsic muscles open and close the glottis and control the amount of tension applied to the vocal folds and ligaments.

Function Intrinsic muscle

Abduction of vocal cords

Opens glottis

  • Posterior cricoarytenoid muscles

Adduction of vocal cords

Closes glottis

  • Lateral cricoarytenoid muscles
  • Transverse arytenoid muscle
  • Oblique arytenoid muscle
  • Cricothyroid muscle
  • Thyroarytenoid muscle

Contraction of vocal cords

Heightens pitch of voice

Relaxation of vocal cords

Lowers pitch of voice

  • Thyroarytenoid muscle

Fine adjustments

The paired posterior cricoarytenoid (PCA) muscles are the only muscles responsible for opening (abducting) the vocal cords. Paralysis of the PCA causes the vocal folds to close, potentially leading to asphyxiation.

Vasculature

Arteries
Veins
  • Superior laryngeal veins and inferior laryngeal veins
Lymphatics

Innervation

Except for the cricothyroid, all intrinsic muscles of the larynx are innervated by the recurrent laryngeal nerve. The cricothyroid is innervated by the superior laryngeal nerve. Denervation of the cricothyroid occurs in up to 30% of thyroid dissections and causes monotone voice and impaired ability to produce pitched sounds.
The recurrent laryngeal nerve is at risk of injury during thyroid surgery because it passes close to the thyroid gland on its ascent to the larynx. While unilateral vocal cord paresis leads to paramedian positioning of the vocal cords, which may cause hoarseness, acute bilateral paralysis is a medical emergency that may require a tracheotomy to secure the airway.

Smoking increases the risk of squamous metaplasia at the transitional zone between respiratory and stratified squamous nonkeratinized epithelium, which may progress to squamous cell carcinoma of the larynx.