Learning objective

By the end of this article, the learner should be able to describe the anatomy of the larynx, including its anatomical position, internal organisation, vascular supply, innervation, and key clinical correlations.

Overview of the larynx

The larynx (voice box) is an organ located in the anterior region of the neck. It forms part of the respiratory tract and performs several vital functions, including:

Phonation (voice production)
Protection of the lower respiratory tract during swallowing
Initiation of the cough reflex

Structurally, the larynx consists primarily of cartilage, connected by ligaments and membranes. Its intrinsic muscles alter the position and tension of the laryngeal components, allowing precise control of breathing and voice production.

In this article, we will examine the anatomy of the larynx, focusing on its location, structure, vasculature, innervation, and clinical relevance.

Anatomical position and relations

The larynx is situated in the anterior compartment of the neck, suspended from the hyoid bone, and extends vertically from vertebral levels C3 to C6.

Inferiorly, it is continuous with the trachea
Superiorly, it opens into the laryngeal part of the pharynx

Anteriorly, the larynx is covered by the infrahyoid muscles, while laterally it is closely related to the lobes of the thyroid gland. Major blood vessels of the neck ascend on either side of the larynx.

Posterior to the larynx lies the oesophagus, a relationship of important clinical significance. During emergency airway management, pressure may be applied to the cricoid cartilage to compress the oesophagus and reduce the risk of gastric regurgitation—a technique known as cricoid pressure (Sellick’s manoeuvre).

Anatomical structure

The larynx is composed of a cartilaginous skeleton stabilised by ligaments and membranes. Movement of the laryngeal cartilages is controlled by intrinsic muscles, which regulate phonation and airflow.

Internal divisions of the laryngeal cavity

The internal cavity of the larynx is divided into three regions:

Supraglottis – extends from the inferior surface of the epiglottis to the vestibular (false vocal) folds
Glottis – contains the true vocal cords and extends approximately 1 cm below them
- The opening between the vocal cords is the rima glottidis, whose size is altered during breathing and speech
Subglottis – extends from the inferior border of the glottis to the inferior border of the cricoid cartilage

The laryngeal cavity is lined predominantly by pseudostratified ciliated columnar epithelium. An important exception is the true vocal cords, which are covered by stratified squamous epithelium to withstand mechanical stress during phonation.

Vasculature

Arterial supply

The larynx receives arterial blood from two main sources:

Superior laryngeal artery – a branch of the superior thyroid artery, accompanying the internal laryngeal nerve
Inferior laryngeal artery – a branch of the inferior thyroid artery, accompanying the recurrent laryngeal nerve

Venous drainage

The superior laryngeal vein drains into the internal jugular vein via the superior thyroid vein
The inferior laryngeal vein drains into the left brachiocephalic vein via the inferior thyroid vein

Innervation

Innervation of the larynx is provided by branches of the vagus nerve (CN X):

Recurrent laryngeal nerve
- Motor: all intrinsic laryngeal muscles except the cricothyroid
- Sensory: infraglottic region
Superior laryngeal nerve
- Internal branch: sensory innervation to the supraglottis
- External branch: motor innervation to the cricothyroid muscle

Clinical relevance – vocal cord paralysis

The vocal cords are essential for speech production and are controlled by the intrinsic muscles of the larynx, most of which are innervated by the recurrent laryngeal nerve.

Due to its long anatomical course, the recurrent laryngeal nerve is vulnerable to injury. Common causes include:

Apical lung tumours
Thyroid malignancy
Aortic aneurysm
Cervical lymphadenopathy
Iatrogenic injury (especially during thyroid surgery)

Clinical presentation

Unilateral recurrent laryngeal nerve palsy results in hoarseness, with partial preservation of speech due to compensation by the unaffected cord.
Bilateral palsy causes impaired phonation and compromised airway patency.
Bilateral partial injury may result in both vocal cords becoming fixed in the adducted position, completely obstructing the airway and requiring emergency surgical intervention.