Larynx

Abstract

Gross anatomy

Overview

  • The larynx is a hollow, tube-shaped organ continuous with the trachea below and the pharynx above in the anterior compartment of the neck.
  • Most superior part of the lower respiratory tract
  • Extends from C3–C6
  • Muscles and ligaments support the cartilaginous skeleton of the larynx

Function

Regions of the laryngeal cavity

Cartilages

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

Adduction of vocal cords

Closes glottis

Contraction of vocal cords

Heightens pitch of voice

Relaxation of vocal cords

Lowers pitch of voice

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
  • Area above the vocal folds: lymphatic drainage along the superior laryngeal artery → deep cervical nodes at carotid bifurcation
  • Area below the vocal folds: lymphatic drainage along the inferior thyroid artery → subclavian nodes

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.

Microscopic anatomy

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.

Embryology

Function

  • Physiologic respiration
  • Forced respiration
  • Phonation, articulation: arytenoid cartilages and vocal folds abducted → air forced through the closed rima glottidisvocal folds vibrate against each other → production of sound → modification by upper parts of airway and oral cavity
  • Effort closure (the retention of air in the thoracic cavity, e.g., during heavy lifting)
  • Swallowing: rima glottidis, rima vestibuli, and vestibule are closed and larynx moves up and forward → epiglottis swings downward to close the laryngeal inlet → opening of the esophagus posterior to the cricoid cartilage → prevention of liquids or food being aspirated

Clinical significance

last updated 09/07/2018
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