Vocal Cords (Vocal Folds)

What Are the Vocal Cords?

The vocal cords are a pair of soft, flexible folds inside the larynx that can open, close and vibrate, and they are the source of the human voice. Anatomists prefer the name vocal folds, because they are not loose strings but ledges of tissue that jut in from the side walls of the airway.

Every breath passes between them. The gap they leave is called the rima glottidis, and the folds plus that gap together make up the glottis. Because they guard the entrance to the trachea, the vocal cords are both a voice organ and a working part of the airway.

Larynx vs vocal cords

The larynx is the whole voice box, a frame of nine laryngeal cartilages with its muscles, ligaments and lining, while the vocal cords are just one pair of folds inside it. In other words, the vocal cords are part of the larynx, in the same way that strings are part of a guitar.

Explained simply

Imagine two curtains hung across a doorway. When you breathe they are pulled apart so air can pass. When you speak they are drawn together, and air pushing through makes their edges flutter and buzz. When you swallow they are shut tight, like a door locked against food.

Where Are the Vocal Cords Located?

The vocal cords are located in the middle of the larynx, directly behind the Adam's apple, where they stretch from front to back across the airway at the level of the glottis. They lie below the epiglottis and the false vocal cords and above the subglottis, the short space that leads down into the trachea.

Each fold attaches in front to the inner surface of the thyroid cartilage, close to the midline, where the two folds meet at a point called the anterior commissure. At the back, each one ends on the vocal process of an arytenoid cartilage, which can rotate and slide. The front of each fold therefore stays fixed, and the back swings open and shut like a gate on a hinge.

Seen from above with a mirror or a camera, the two folds form a V, with its point at the front. Between the true vocal cords and the false ones above sits a small side pocket on each side called the laryngeal ventricle. In adults the glottis is the narrowest part of the airway.

Vocal Cords Anatomy: What Are They Made Of?

Each vocal cord is made of a thin surface epithelium, a layered connective tissue called the lamina propria and, at its core, the vocalis muscle, arranged so that a loose outer cover can ripple over a firmer body. This layered design is what lets the folds vibrate hundreds of times a second without tearing.

The layers

• Epithelium: a non-keratinized stratified squamous layer, tougher than the ciliated respiratory epithelium lining most of the airway, which gives the folds their pearly white look.
• Superficial lamina propria: a loose, jelly-like layer, also called Reinke's space, that lets the surface slide and wave freely.
• Intermediate and deep lamina propria: layers rich in elastic and then collagen fibers that together form the vocal ligament.
• Vocalis muscle: the inner part of the thyroarytenoid muscle, which stiffens or slackens the fold.

Muscles, nerves and blood supply

The small intrinsic muscles of the larynx move the arytenoid and thyroid cartilages to open, close, stretch and shorten the folds. All of them are supplied by the recurrent laryngeal nerve except the cricothyroid muscle, which is supplied by the external branch of the superior laryngeal nerve. Blood reaches the folds through the superior and inferior laryngeal arteries, branches of the thyroid arteries, and the true folds have very few lymph vessels.

What Is the Function of the Vocal Cords?

The vocal cords have three main functions: they open to let air in and out during breathing, they close to protect the lower airway, and they vibrate to produce voice for speech and singing. Their function in the respiratory system comes first; voice is a later use of the same valve.

Vocal cords function in the respiratory system

During quiet breathing the folds rest partly apart. With each breath in they widen slightly, and during a deep or forceful breath the posterior cricoarytenoid muscles pull them wide open to lower resistance to airflow. During breathing out they drift a little closer together, which slows the outflow of air. Through these small movements the vocal cords help control how fast air enters and leaves the lungs.

Protecting the airway

When you swallow, the vocal cords close tightly together with the false vocal cords and the epiglottis, so food and drink are steered into the esophagus instead of the trachea. They also make a cough possible: the folds shut, pressure builds in the chest, and then they burst open to blast out mucus or a foreign particle. Holding the folds closed also fixes the chest when lifting something heavy.

Vocal folds function in speech

To make voice, the folds are brought together and air from the lungs pushes them apart; their elasticity and the drop in pressure between them pull them back, and the cycle repeats, producing a buzzing sound. A typical adult male speaking voice vibrates around 100 to 150 times per second, and a female voice around 180 to 250 times. The throat, mouth and nose then shape that buzz into words, as explained on our page on how the voice is produced.

What Do the False Vocal Cords (Vestibular Folds) Do?

The false vocal cords, or vestibular folds, are a second, thicker pair of folds just above the true vocal cords whose main function is to help seal the airway and to keep the true folds moist; they do not normally vibrate in speech. They contain the vestibular ligament and only a little muscle.

Each vestibular fold is lined with respiratory epithelium and contains many mucous glands. Their secretions drain into the laryngeal ventricles and coat the true vocal cords, which have no glands of their own and need constant lubrication to vibrate smoothly. During swallowing, coughing and straining, the false folds close as a second barrier above the true ones.

In some styles of singing, such as certain kinds of throat singing, the false folds can be made to vibrate on purpose and produce a rough, low sound. In ordinary speech, voice made with the false folds is a sign that the true folds are not closing properly.

How Do the Vocal Cords Change With Age?

The vocal cords are short and high in the neck in infants, grow quickly at puberty, especially in boys, and become thinner and less elastic in older age, which is why the voice changes across life. Their length is the main reason adult men usually have deeper voices than women and children.

At puberty the male larynx enlarges, the thyroid cartilage forms a visible Adam's apple and the vocal cords become longer and thicker, so the pitch drops by roughly an octave; the voice can crack while the muscles adjust. Girls' vocal cords also grow, but less, and their pitch drops only a little. In older adults the vocalis muscle can thin and the folds may bow slightly, making the voice weaker or breathier, a change sometimes called presbyphonia.

Common Conditions That Affect the Vocal Cords

Most conditions of the vocal cords cause hoarseness, a change in the voice, or noisy breathing, and they range from short-term swelling to lasting nerve damage. Our respiratory diseases section covers airway conditions, and hoarseness that lasts more than a few weeks is a reason to see a doctor.

• Laryngitis: inflammation and swelling of the folds, often from a cold or voice strain.
• Vocal cord nodules: small, firm bumps on both folds, usually from heavy voice use, at the point where the folds strike hardest.
• Polyps and cysts: soft growths, usually on one fold, that stop the edges from meeting cleanly.
• Reinke's edema: fluid swelling of the superficial lamina propria, strongly linked to smoking, which lowers the voice.
• Vocal cord paralysis: loss of movement of one or both folds after damage to the recurrent laryngeal nerve; the left nerve, which loops down around the aorta, is affected more often.
• Vocal cord dysfunction: the folds close when they should open during breathing in, which can be mistaken for asthma.
• Laryngeal cancer: the glottis is the most common site of cancer of the larynx, and tobacco smoke is the main risk factor.