Science Fair Project Encyclopedia
The larynx (IPA 'lŠɹɪŋks) is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal cords, and is situated at the point where the upper tract splits into the trachea and the esophagus.
The larynx rests in a frame of cartilage bound by ligaments and muscle. At the front is the thyroid cartilage, also called the thyroid lamina, creating the prominence of the Adam's apple in humans. Below the thyroid cartilage is a ring-shaped cartilage called the cricoid which forms the connection to the traches. The criciod cartilage resembles a signet ring (Narrow in back, broader in front). Above the larynx is a supporting bone called the hyoid, which moves the larynx during swallowing. The hyoid is the only floating bone in the body; it is not 'attached' to any other bones. The epiglottis is another cartilage that extents upwards behind the back of the tongue and projects down through the hyoid bone.
Within the larynx there is the supraglottis at the top, consisting of the epiglottis, the aryepiglottic folds, the false vocal cords and the ventricle. In the middle is the glottis, within which are the two true vocal folds (also called vocal cords), thin muscular strips coated in mucosa. One end of the folds is joined to the thyroid cartilage at the anterior commissure, the other end of each fold is joined to the arytenoid cartilage which move within the posterior cricoid, muscles attached to the arytenoid pull the folds apart during breathing and brings them close together during sound production. The lowest portion of the larynx is the subglottis.
During swallowing the larynx (and the epiglottis) close to prevent swallowed material entering the lungs, there is also a strong cough reflex to protect the lungs. Sensation is transferred by the superior laryngeal nerve (glottis and supraglottis) and the recurrent laryngeal nerve (subglottis and muscles), both branches of the vagus nerve.
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