Anatomy of the Larynx

The Larynx

• The larynx is an organ located below the tongue and hyoid bone, and between the great blood vessels of the neck, at the level of the fourth, fifth, and sixth cervical vertebrae.
• It provides a protective sphincter at the inlet of the air passages and is responsible for voice production.
• The larynx opens above into the laryngeal part of the pharynx and below is continuous with the trachea.

Cartilages of the Larynx

• Thyroid cartilage: the largest cartilage of the larynx, consisting of two laminae of hyaline cartilage that meet in the midline, forming a prominent V angle (Adam's apple).
• Cricoid cartilage: a ring-shaped cartilage with a broad plate behind and a shallow arch in front, articulating with the inferior cornu of the thyroid cartilage.
• Arytenoid cartilages: two small, pyramid-shaped cartilages articulating with the upper border of the cricoid cartilage, with a vocal process that projects forward and gives attachment to the vocal ligament.
• Corniculate cartilages: two small, conical-shaped cartilages articulating with the arytenoid cartilages, giving attachment to the aryepiglottic folds.
• Cuneiform cartilages: two small, rod-shaped cartilages found in the aryepiglottic folds, strengthening them.
• Epiglottis: a leaf-shaped lamina of elastic cartilage lying behind the root of the tongue, attached to the back of the thyroid cartilage and the arytenoid cartilages.

Membranes and Ligaments of the Larynx

• Thyrohyoid membrane: connects the upper margin of the thyroid cartilage to the hyoid bone.
• Cricotracheal ligament: connects the cricoid cartilage to the first ring of the trachea.
• Quadrangular membrane: extends between the epiglottis and the arytenoid cartilages, forming the vestibular ligament.
• Cricothyroid ligament: connects the lower margin to the upper border of the cricoid cartilage.

Cavity of the Larynx

• The cavity of the larynx extends from the inlet to the lower border of the cricoid cartilage, where it is continuous with the cavity of the trachea.
• It is divided into three regions: the vestibule, the middle region, and the lower region.

Sinus and Saccule of the Larynx

• The sinus of the larynx is a small recess on each side of the larynx, situated between the vestibular and vocal folds.
• The saccule of the larynx is a diverticulum of mucous membrane that ascends from the sinus, lubricating the vocal cords.

Muscles of the Larynx

• Extrinsic muscles: move the larynx up and down during swallowing, attached to the hyoid bone.
• Intrinsic muscles: divide into two groups, controlling the movement of the vocal folds and the opening of the glottis.

Voice Production in the Larynx

• The intermittent release of expired air between the adducted vocal folds results in their vibration and the production of sound.
• The frequency, or pitch, of the sound is determined by changes in the length and tension of the vocal ligaments.
• The quality of the voice depends on the resonators above the larynx, namely, the pharynx, mouth, and paranasal sinuses.

Mucous Membrane of the Larynx

• The mucous membrane of the larynx lines the cavity and is covered with ciliated columnar epithelium.
• On the vocal cords, the mucous membrane is covered with stratified squamous epithelium.

Nerve Supply of the Larynx

• Sensory nerves: above the vocal cords, the internal laryngeal branch of the superior laryngeal branch of the vagus; below the vocal cords, the recurrent laryngeal nerve.
• Motor nerves: all intrinsic muscles of the larynx except the cricothyroid muscle are supplied by the recurrent laryngeal nerve; the cricothyroid muscle is supplied by the external laryngeal branch of the superior laryngeal branch of the vagus.

Blood Supply of the Larynx

• Upper half of the larynx: the superior laryngeal branch of the superior thyroid artery.
• Lower half of the larynx: the inferior laryngeal branch of the inferior thyroid artery.

Lymph Drainage of the Larynx

• The lymph vessels drain into the deep cervical group of nodes.