Joints of the Larynx
The joints of the larynx are the governors of this complex organ that both stabilize and mobilize all of its working parts to allow swallowing, speech and breathing. In this article, all of the joints, ligaments and membranes that make up this essential and astounding anatomical structure will be discussed, along with a small overview of the pathological disorders that may be inflicted upon the larynx.
There are two sets of paired joints which aid the movement of the vocal cords in the larynx.
The first pair are the cricothyroid joints which are formed by the articulation between the cricoid cartilage and the thyroid cartilage. In this joint the thyroid cartilage glides and rotates laterally and either superiorly or inferiorly, which in turn changes the length of the vocal chords. When this movement occurs, the tension on the vocal chords changes, resulting in a different pitch of sound in the human voice.
The second pair of joints are the cricoarytenoid articulations which create the movement of the arytenoid cartilage upon the lamina of the cricoid cartilage. The arytenoid cartilages slide both towards and away from each other, they rotate upon their own axis and they tilt forwards and backwards, gaging on the whole a very wide range of movement.
The ligaments of the larynx are classified according to their position, which is either intrinsic or extrinsic. There are two major intrinsic ligaments and five major extrinsic ligaments.
The major intrinsic ligaments include the vocal ligament and the conus elasticus. Together they both help form the true vocal cord. The vocal ligament is located between the arytenoid and the thyroid cartilages. The conus elasticus stretches superiorly from the thyroid cartilage, the vocal ligament and the arytenoid cartilage inferiorly to the upper border of the cricoid cartilage.
The major extrinsic ligaments include a pair of lateral thyrohyoid ligament and a median thyrohyoid ligament which help compose the thyrohyoid membrane by stretching between the thyroid cartilage and the hyoid bone. Also, the median cricothyroid ligament which stretches between the cricoid cartilage and the thyroid cartilage. Finally, the cricotracheal ligament that runs from the inferior border of the cricoid cartilage down to the first tracheal ring.
There are three laryngeal membranes, which are known as the quadrangular membrane, the thyrohyoid membrane and the mucous membrane.
The quadrangular membrane is comprised of nonelastic connective tissue which is attached to the lateral margins of the arytenoid cartilages and the epiglottis. At its inferior edge the border is mobile and is known as the vestibular ligament or false vocal cord. It is covered by the vestibular fold and is just above the vocal fold and it extends between the thyroid cartilage and the arytenoid cartilages. The superior border is also mobile and forms the aryepiglottic ligament which is covered by mucosa and is named the aryepiglottic fold.
The thyrohyoid membrane stretches between the superior border and the superior horns of the thyroid cartilage and the hyoid bone. It is pierced by the laryngeal vessels and the internal laryngeal nerve which innervates the intrinsic parts of the larynx.
Lastly, the mucous membrane is the stratified squamous epithelium that covers all the inner walls of the larynx save the true and aryepiglottic folds.
Acute laryngotracheobronchitis, which is simply known as croup, is an inflammation of the larynx, the trachea and the epiglottis. It is potentially life threatening and is usually seen in infants. Chronic forms also exist that can ensue for months at a time, weakening the respiratory tract and exposing it to the risk of infestation by other microbes. The most common form of infection is by viral means and the most obvious clinical symptoms are a harsh cough and an audible inspiratory stridor.