The voice box is the common term for the mammalian larynx, a structure located in the neck that serves multiple functions. Only mammals have vocal folds, commonly called vocal chords, within the larynx. These are responsible for the ability of mammals to vocalize and humans to speak. The human voice box is located at the upper front of the neck and is made up of cartilage, connective tissue, mucous membrane and muscle. In addition to vocalizations, the voice box functions to keep the airway open and prevent food from passing into the trachea.
Nine cartilages form the structure of the larynx, six in pairs and three single. These are joined by connective tissues and moved with muscles. A mucous membrane forms a continuous lining from the mouth and pharynx above the larynx through the trachea extending towards the lungs. After puberty, the male's larynx becomes significantly larger than the female's and makes the characteristic Adam's apple at the front of a man's neck. Centered within the larynx are the vocal folds, which are made of two strong ligaments and responsible for the production of sound.
Serving as a guard to the lower respiratory tract, the main function of the voice box is to provide a safe, open passage for air. While breathing, the passageway remains open, with the epiglottis upright and vocal folds open. When eating, the epiglottis at the top of the larynx closes, as do the vocal folds to assure food does not pass into the airway and cause choking. Vocalizations are produced by complex interactions between the larynx, the lungs and chest, and the nose and mouth. Unique to humans, speech is formed by these interactions with the vocal folds creating the pitch of the voice.
A healthy larynx has white vocal folds that meet symmetrically at the center of the larynx, while the rest of the voice box is a healthy pink color. This is in contrasted to the appearance of a larynx that is diseased. One of the most common disorders is the presence of nodules or polyps on the vocal folds. These nodules prevent the vocal folds from meeting completely, giving the voice a rough or raspy sound as air escapes. Larynx surgery can correct nodules and some other voice box problems.
Other larynx problems include vocal fold polyps, which are more common in men and also prevent the vocal chords from meeting symmetrically, giving the voice a hoarse or raspy sound. Laryngitis is the swelling of the larynx and interferes with the production of vocalizations. It can be temporary during a cold or flu or chronic from smoking or misuse of the vocal folds. Frequently, vocal folds thin as aging occurs, causing gaps between them and a change in vocalizations. Another issue is cancer of the larynx, the primary cause of which is believed to be the chronic use of tobacco and alcohol.