The larynx, commonly known as the voice box, is a specialized organ located in the neck that serves a dual purpose. It functions as a protective gateway, ensuring air passes into the trachea while food and liquid are diverted toward the esophagus during swallowing. The larynx is also the primary mechanism for generating vocal sound. This complex structure is built upon a framework of nine cartilages, which provide stability and flexibility for movement.
Defining the Laryngeal Framework
The foundation of the voice box is constructed from three large, unpaired cartilages. The thyroid cartilage (Adam’s apple) is the largest, providing shield-like protection for internal structures. Below it sits the cricoid cartilage, the only complete ring of cartilage in the airway, resembling a signet ring. The leaf-shaped epiglottis acts as a flap, folding down to cover the airway opening during swallowing. These larger structures form the scaffolding within which smaller, paired cartilages control the vocal cords.
Precise Location and Structure of the Arytenoids
The arytenoid cartilages are a pair of small, pyramid-shaped structures located at the back of the larynx. They are positioned on the superior, posterior aspect of the cricoid cartilage’s broad plate, forming the mobile cricoarytenoid joint. Being paired, they provide symmetrical control to the vocal folds.
Each arytenoid is a three-sided pyramid with a distinct base and apex. The base is the articulating surface, which sits directly on the cricoid cartilage. At the top is the apex, which points upward and is sometimes capped by a corniculate cartilage.
The arytenoid cartilage features two projections that extend from its base. The vocal process points forward toward the thyroid cartilage and serves as the attachment point for the vocal ligament. The muscular process extends laterally and provides an anchor point for the intrinsic muscles that control the movement of the arytenoids.
The Mechanical Role in Sound Production
The function of the arytenoid cartilages is to manipulate the position and tension of the vocal folds for breathing and voice production. They articulate with the cricoid cartilage in a synovial joint, allowing for two main movements: sliding and rocking. This precise articulation enables the fine adjustments necessary for speech and singing.
Muscles attach to the muscular process of the arytenoids and, when contracted, cause the cartilages to rotate and slide. When inhaling, the posterior cricoarytenoid muscles contract, externally rotating the arytenoids. This rotation pulls the vocal processes and attached vocal folds apart (abduction), which opens the space between the cords to allow air to flow freely into the lungs.
Conversely, for voice production or during swallowing, the lateral cricoarytenoid and interarytenoid muscles contract. This action causes the arytenoids to internally rotate and move closer together (adduction). Adduction brings the vocal folds into the midline position, where air passing through causes them to vibrate and create sound. The ability of the arytenoids to rock, glide, and pivot makes them the mechanical regulators of the vocal cords.