The larynx, often referred to as the voice box, is a complex structure located in the anterior neck, above the trachea. This organ serves as a passageway for air, connecting the pharynx to the trachea, and plays a fundamental role in sound production. Its framework is primarily composed of various cartilages, firm yet flexible connective tissue providing structure and mobility. These cartilages are interconnected by muscles and ligaments, allowing for precise movements that facilitate breathing and vocalization.
The Major Unpaired Cartilages
The largest laryngeal cartilage is the thyroid cartilage, forming the prominent anterior and lateral walls of the larynx. Its shield-like shape provides protection to the internal structures. The anterior fusion of its two laminae creates a noticeable ridge known as the laryngeal prominence, or “Adam’s apple,” which tends to be more pronounced in adult males due to hormonal influences on its growth.
Immediately inferior to the thyroid cartilage is the cricoid cartilage, the only complete ring of cartilage in the larynx. This signet-ring shaped structure forms the base of the larynx, supporting other laryngeal cartilages. Its complete circular form maintains an open airway, preventing collapse during breathing.
The epiglottis is a leaf-shaped piece of elastic cartilage at the top of the larynx, behind the root of the tongue. It extends upwards, with its stalk attaching to the inner surface of the thyroid cartilage. This placement allows it to act as a protective lid for the airway.
The Minor Paired Cartilages
The arytenoid cartilages are a pair of small, pyramid-shaped structures atop the posterior superior border of the cricoid cartilage. These cartilages are mobile, serving as primary attachment points for the vocal folds. Their ability to pivot and slide is fundamental for adjusting the vocal folds.
Superior to the arytenoid cartilages are the corniculate cartilages, small, cone-shaped structures resting on the apices of the arytenoids. They contribute to the structure of the laryngeal inlet. The cuneiform cartilages are embedded within the aryepiglottic folds. These small, rod-shaped cartilages provide support to the laryngeal entrance.
Function in Voice and Breathing
The coordinated action of these cartilages is fundamental for voice production (phonation). The arytenoid cartilages, through pivoting and sliding motions, influence the tension, length, and position of the vocal folds. Muscles attached to these cartilages manipulate their position, causing the vocal folds to adduct (come together) or abduct (move apart). As air from the lungs passes through the narrowed glottis, it causes the adducted vocal folds to vibrate, producing sound. Changes in the tension and length of the vocal folds, controlled by these cartilages, allow for variations in pitch and volume.
Beyond vocalization, the laryngeal cartilages are also involved in respiration. During quiet breathing, the arytenoid cartilages rotate laterally, moving the vocal folds apart. This action widens the glottis, creating an open airway allowing air passage. The cricoid cartilage’s complete ring structure maintains this open airway.
The larynx and its cartilages also provide airway protection, especially during swallowing. As food or liquid is ingested, the entire larynx moves upward and forward. This movement causes the epiglottis to fold down like a lid, covering the laryngeal inlet. This protective mechanism ensures that food and liquids are directed safely into the esophagus and prevented from entering the trachea and lungs.
Changes with Age
Over a person’s lifetime, the cartilages of the larynx undergo ossification. This involves the gradual replacement of hyaline cartilage, like the thyroid and cricoid, with bone tissue. This process begins in early adulthood, often around the third decade of life, and progresses with age. The extent of ossification varies between individuals and sexes.