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The larynx: structure, topography, blood and nerves supply, compartments, cartilages, cavities of larynx. Mechanism of voice production

The larynx, commonly called the voice box, is an organ in the neck of mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume. The larynx houses the vocal folds, which are essential for phonation. The vocal folds are situated just below where the tract of the pharynx splits into the trachea and the esophagus. The larynx is situated on the level of the fourth, fifth and sixth cervical vertebrae immediately below the hyoid bone, on the anterior surface of neck and form here a clearly visible eminence.

Cartilages: 1) Cricoid cartilage is hyaline and shaped like a signet ring with a wide plate at the back and arch. 2) Thyroid cartilage is the largest of the laryngeal cartilage and consist of two lamina. 3) The arytenoid cartilages are directly related to the vocal cords and muscles. 4) Corniculate cartilages are seated on the apices of the arytenoid cartilages. 5) Epiglottis cartilage is a leaf-shaped lamina of elastic cartilaginous tissue situated in front of larynges and directly behind the root of the tongue.

The laryngeal cavity (cavity of the larynx) extends from the laryngeal entrance downwards to the lower border of the cricoid cartilage where it is continuous with that of the trachea.

Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness.

Arteries: The superior and inferior laryngeal arteries supply the majority of blood to the larynx. The superior laryngeal artery originates from the superior thyroid branch of the external carotid artery and enters the larynx with the internal branch of the superior laryngeal nerve through the lateral aperture of the thyroid membrane. The inferior laryngeal artery originates from the inferior thyroid branch of the thyro-cervical trunk, which is a branch of the subclavian artery. Veins: The superior and inferior laryngeal veins drain the larynx and share the same course as the arteries. The superior laryngeal veins drain into the superior thyroid veins, which empty into the internal jugular veins. The inferior laryngeal veins drain into the inferior thyroid veins. Superior laryngeal nerve: arise from the inferior ganglia of the vagus nerve and receive a branch from the superior cervical sympathetic ganglion on each side in the upper neck.

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