Larynx (Voice Box)

What Is the Larynx?

The larynx is the hollow, cartilage-walled organ at the top of the windpipe that works as the airway's gatekeeper and as the body's sound source. It is also known as the voice box, and the name is pronounced "LAIR-inks" (not "LAR-nix"). Air reaches it from the pharynx (throat) and leaves it through the trachea on the way to the lungs. Because the paths for air and for food cross just above it, the larynx belongs to the breathing system but works closely with the digestive system as well.

Most anatomy books place the larynx at the lower end of the upper respiratory tract, together with the nose, nasal cavity and pharynx. Some textbooks count it as the first part of the lower tract instead, because everything from the larynx down is normally kept free of food and germs.

What does the larynx look like?

From the front, the larynx looks like a short, slightly flattened tube with a pointed ridge, the Adam's apple, in the middle. Inside, its passage narrows to a slit between two pale, shiny bands, the vocal folds, which open into a V shape when we breathe and close into a straight line when we speak. Above them sits the leaf-shaped epiglottis, which stands up behind the root of the tongue.

Explained simply

Think of the larynx as a valve with a built-in musical instrument. When you breathe, the valve stays open so air can flow freely. When you swallow, it snaps shut so food slides past into the food pipe. When you talk, it closes almost all the way, and air from your lungs makes the two edges of the valve buzz like the lips of a trumpet player.

Where Is the Larynx Located?

The larynx is located in the front of the neck, in the midline, below the hyoid bone and above the trachea. In adults it spans the third to sixth cervical vertebrae (C3 to C6), and it lies directly in front of the lowest part of the throat, the laryngopharynx, into which its upper opening faces.

Where is the larynx in relation to the pharynx and trachea?

• Above: the larynx hangs from the U-shaped hyoid bone by the thyrohyoid membrane, and its inlet opens backward into the laryngopharynx.
• Below: at the lower border of the cricoid cartilage, level with C6, it continues into the trachea.
• Behind: the laryngopharynx, which leads down into the esophagus, the food pipe.
• In front: skin, fat and the thin infrahyoid "strap" muscles of the neck.
• To the sides: the lobes of the thyroid gland, which wrap around the lower larynx and upper trachea, and the large blood vessels of the neck.

Where is the larynx located in the throat?

In everyday language the whole front of the neck is "the throat", but anatomically the larynx sits in front of the throat (pharynx), not inside it. You can feel it by placing a finger on the Adam's apple and swallowing: the whole larynx moves up and then down again. Just below the Adam's apple lies a soft gap, the cricothyroid membrane, and below that the firm ring of the cricoid cartilage.

The larynx sits higher in babies than in adults. In a newborn it lies roughly opposite the first to fourth cervical vertebrae, and it gradually descends through childhood, which changes both breathing and the sound of the voice.

What Is the Larynx Made Of?

The larynx is made of 9 cartilages, 3 single and 3 paired, held together by joints, ligaments and membranes, moved by small muscles and lined with mucous membrane. The cartilages give it a stiff frame that cannot collapse when we breathe in, while the joints let some of them tilt and slide to change the shape of the airway.

The unpaired cartilages

The thyroid cartilage is the largest. It is formed by two flat plates (laminae) that meet in front at an angle, creating the laryngeal prominence, or Adam's apple. The angle is sharper, about 90 degrees, in men and wider, about 120 degrees, in women, which is why the prominence is easier to see in men. Its upper horns are tied to the hyoid bone, and its lower horns form small joints with the cricoid cartilage.

The cricoid cartilage lies below it and is shaped like a signet ring, narrow in front and broad at the back. It is the only complete ring of cartilage anywhere in the airway, so it keeps the bottom of the larynx open at all times. The epiglottis is a flexible, leaf-shaped plate of elastic cartilage attached to the back of the thyroid angle and rising behind the tongue.

The paired cartilages

The two arytenoid cartilages are small pyramids that sit on the upper back edge of the cricoid lamina. Each has a vocal process, to which the vocal ligament attaches, and a muscular process, where the muscles that move it pull. Because the arytenoids can glide and rotate, they open and close the vocal folds. The tiny corniculate cartilages perch on the tips of the arytenoids, and the rod-like cuneiform cartilages lie inside the aryepiglottic folds, where they stiffen the edges of the laryngeal inlet.

Membranes and ligaments

The thyrohyoid membrane slings the larynx from the hyoid bone, and the cricotracheal ligament joins it to the first ring of the trachea. Inside, two sheets of connective tissue shape the cavity: the quadrangular membrane, whose free lower edge is the vestibular ligament inside each false vocal cord, and the conus elasticus, whose thickened upper edge is the vocal ligament inside each true vocal cord. The front of the conus elasticus forms the cricothyroid ligament, the soft spot below the Adam's apple used for an emergency airway when the airway above is blocked.

Larynx Anatomy: Inside the Laryngeal Cavity and Vocal Cords

The inside of the larynx, the laryngeal cavity, runs from the laryngeal inlet at the top to the lower edge of the cricoid cartilage, and two pairs of folds divide it into three levels: the supraglottis, the glottis and the subglottis.

• Laryngeal inlet: the oval entrance, bordered by the epiglottis in front, the aryepiglottic folds at the sides and the notch between the arytenoids at the back.
• Supraglottis: everything above the true vocal folds, including the epiglottis, the vestibule, the vestibular folds (false vocal cords) and the laryngeal ventricles, two small side pockets between the false and true folds.
• Glottis: the true vocal folds and the gap between them, called the rima glottidis. In adults this is the narrowest part of the airway, and its width changes constantly with breathing, speaking and swallowing.
• Subglottis: the short space from below the vocal folds to the lower border of the cricoid cartilage, where the larynx becomes the trachea.

True and false vocal cords

The true vocal folds (vocal cords) are two smooth, pearly-white bands that stretch from the inside of the thyroid angle in front to the vocal processes of the arytenoids at the back. Each contains the vocal ligament and the vocalis muscle, the inner part of the thyroarytenoid. The false vocal folds lie just above them; they are thicker, pinker and contain only a little muscle, so they do not normally vibrate in speech. Their main job is to help seal the airway, for example when holding the breath to lift something heavy.

Larynx histology: the lining

Most of the larynx is lined by respiratory epithelium, a pseudostratified ciliated columnar layer with mucus-making goblet cells, the same lining found in the nose and trachea. The true vocal folds and the upper part of the epiglottis are different: they are covered by non-keratinized stratified squamous epithelium, a tougher, many-layered surface that withstands the constant rubbing of vibration. Under the vocal fold epithelium lies a loose, jelly-like layer called Reinke's space, which lets the surface ripple freely over the deeper ligament and muscle.

The thyroid, cricoid and most of the arytenoid cartilages are hyaline cartilage, while the epiglottis, corniculate and cuneiform cartilages and the tips of the vocal processes are elastic cartilage, which bends and springs back.

Muscles, Nerves and Blood Supply of the Larynx

The larynx is moved by two groups of muscles, controlled by two branches of the vagus nerve, and fed by two pairs of laryngeal arteries, with the vocal folds forming the dividing line for both its nerve supply and its lymph drainage.

Extrinsic muscles

Extrinsic muscles run from the larynx or the hyoid bone to structures outside it and move the whole larynx up or down. The suprahyoid group (digastric, geniohyoid, mylohyoid and stylohyoid) lifts the hyoid and larynx during swallowing. The infrahyoid group (omohyoid, sternohyoid, sternothyroid and thyrohyoid) pulls them back down afterward. You can feel this up-and-down movement every time you swallow.

Intrinsic muscles

The intrinsic muscles lie entirely within the larynx and change the position and tension of the vocal folds, which controls the size of the rima glottidis. They are the posterior cricoarytenoid, lateral cricoarytenoid, transverse arytenoid, oblique arytenoid, thyroarytenoid and cricothyroid muscles. All come in left and right pairs except the transverse arytenoid, which is a single muscle bridging the two arytenoids. The table below sums up what each one does.

Nerve supply

Both sensory and motor nerves of the larynx come from the vagus nerve (cranial nerve X) through two branches. The superior laryngeal nerve arises from the inferior ganglion of the vagus and splits in two: its internal branch carries sensation from the lining above the vocal folds, and its external branch supplies a single muscle, the cricothyroid. The recurrent laryngeal nerve supplies every other intrinsic muscle and carries sensation from below the vocal folds. On the left it loops under the arch of the aorta and on the right under the subclavian artery before climbing back up beside the trachea, so the left nerve is longer.

Arteries, veins and lymph

The superior laryngeal artery, a branch of the superior thyroid artery, pierces the thyrohyoid membrane with the internal laryngeal nerve to feed the glands, muscles and lining of the upper larynx. The inferior laryngeal artery comes from the inferior thyroid artery, a branch of the thyrocervical trunk, and enters near the junction of the trachea and esophagus alongside the recurrent laryngeal nerve. Matching veins follow the same paths: the superior laryngeal vein drains through the superior thyroid vein to the internal jugular vein, and the inferior laryngeal vein drains through the inferior thyroid veins to the left brachiocephalic vein.

Lymph from above the vocal folds follows the superior laryngeal artery to the deep cervical lymph nodes, while lymph from below the vocal folds follows the inferior thyroid artery to nodes in front of and beside the upper trachea. The true vocal folds themselves have very few lymph vessels.

What Does the Larynx Do?

The larynx does three main jobs: it keeps an open passage for air between the throat and the lungs, it closes to protect the airway when we swallow, and it produces the sound of the voice. It also powers coughing and lets us hold the breath against a closed airway.

Function of the larynx in the respiratory system

During breathing, air drawn in through the nose or mouth passes down the pharynx, through the larynx and into the trachea, which splits into the two bronchi leading to the lungs. The rigid cartilage frame keeps this passage from collapsing under the suction of a breath in, and the cilia and mucus of its lining help trap dust and sweep it upward. The larynx also adjusts airflow: the vocal folds open wider on a deep breath and narrow slightly as we breathe out, which helps control how fast the lungs empty.

Function of the larynx in the digestive system

The larynx is where the paths for air and food separate, so it must close every time we swallow. In a fraction of a second the larynx is pulled up and forward under the base of the tongue, the epiglottis tips backward over the inlet, the aryepiglottic and false vocal folds squeeze together, and the true vocal folds shut. Breathing stops briefly, food and drink slide around the sides of the inlet into the esophagus, and then everything reopens. If anything still slips into the larynx, its very sensitive lining triggers a strong cough to blast it back out.

Other jobs of the larynx

• Coughing: the vocal folds close, pressure builds in the chest, and the folds fly open to release a burst of air that clears the airway.
• Effort closure: shutting the glottis traps air in the chest and stiffens the trunk for lifting, pushing or straining.
• Voice: vibration of the true vocal folds makes the sound we shape into speech and song.

How Does the Larynx Produce Sound and Speech?

The larynx produces sound when air pushed up from the lungs makes the closed true vocal folds vibrate, chopping the airflow into rapid puffs that we hear as a buzzing tone. That tone is then shaped into words by the pharynx, the oral cavity, the tongue, the lips and the nasal passages.

1. The lateral cricoarytenoid and arytenoid muscles bring the vocal folds together near the midline.
2. Air pressure from the lungs builds up below the closed folds until it pushes them apart.
3. The elastic folds spring back together, partly sucked inward by the fast-moving air, and the cycle repeats many times a second.
4. Each opening releases a tiny puff of air; the stream of puffs is the raw sound of the voice.

What controls pitch and loudness?

Pitch depends on how fast the vocal folds vibrate, which depends on their length, thickness and tension. The cricothyroid muscle tilts the thyroid cartilage forward, stretching and thinning the folds to raise the pitch, while the thyroarytenoid shortens and relaxes them to lower it. In a typical speaking voice the folds vibrate roughly 100 to 150 times per second in adult men and around 200 times per second in adult women. Loudness depends mainly on how hard air is pushed from the lungs and how firmly the folds press together.

The larynx makes the sound, but it does not make words. Vowels and consonants are formed above it, in the resonating spaces of the throat, mouth and nose, which also give each person's voice its own color. That is why people who whisper can still be understood: whispering uses air passing through a partly open glottis without vibration.

Pharynx vs Larynx vs Trachea: What Is the Difference?

The pharynx, larynx and trachea are three linked sections of the airway: the pharynx is the shared muscular throat behind the nose and mouth, the larynx is the cartilage valve and voice box below it, and the trachea is the windpipe that carries air from the larynx down into the chest. Air passes through all three in that order, but only the pharynx also carries food.

The pharynx is divided into the nasopharynx, the oropharynx and the laryngopharynx. Its walls are mostly muscle, which squeezes food downward. The larynx opens off the front of the laryngopharynx, and at that point air turns forward into the larynx while food continues backward into the esophagus. Below the cricoid cartilage, the trachea takes over as a tube of 16 to 20 C-shaped cartilage rings, open at the back where it rests against the esophagus.

In short, the pharynx belongs to both the respiratory and digestive systems, the larynx guards the split between them and makes the voice, and the trachea belongs only to the respiratory system. The comparison table sums up the main differences.

For more detail on the first pair, see our larynx vs pharynx comparison.

How Does the Larynx Develop and Change With Age?

The larynx begins forming in about the fourth week of embryonic life, sits high in the neck at birth, descends during childhood, grows quickly at puberty, especially in boys, and stiffens slowly in later life.

Before birth

The larynx and trachea develop from a groove in the floor of the embryonic foregut, the same bud that later forms the lungs. The laryngeal cartilages and muscles come from the fourth and sixth pharyngeal arches, which is why the larynx is supplied by the nerves of those arches: the superior laryngeal nerve (fourth arch) and the recurrent laryngeal nerve (sixth arch). The epiglottis develops from a separate swelling in the floor of the pharynx. For a while the inside of the larynx is temporarily sealed by its own lining and then opens up again; failure to reopen fully can leave a thin web across the glottis.

Infancy and childhood

A baby's larynx sits high, so the epiglottis can almost touch the soft palate, which helps an infant breathe through the nose while feeding. The infant epiglottis is relatively long, narrow and soft, and the subglottic region is small, so even mild swelling there can noticeably narrow the airway. Over the first years of life the larynx moves down the neck, creating a longer throat above it that adult speech depends on.

Puberty and older age

At puberty the larynx enlarges under the influence of sex hormones. In boys the thyroid cartilage grows forward to form a visible Adam's apple and the vocal folds become longer and thicker, so the voice drops by about an octave, often with a period of cracking. Girls' voices deepen too, but much less. From early adulthood onward the hyaline cartilages slowly begin to calcify and turn partly to bone. In older age the vocal folds can lose some muscle bulk and elasticity, a change called presbylarynx, which may make the voice thinner, breathier or weaker.

Common Conditions That Affect the Larynx

Most disorders of the larynx change the voice, so hoarseness, loss of voice, a sore throat, cough and trouble swallowing are the most common signs. The list below names the main conditions and the part of the larynx each one involves; our respiratory diseases guide covers the wider airway, and anyone with lasting hoarseness or breathing changes should see a doctor.

• Laryngitis: inflammation of the larynx, usually from a viral infection or voice overuse. It can bring a burning or painful throat, swollen glands in the neck, trouble swallowing, tiredness and a mild fever along with hoarseness.
• Croup: a childhood viral infection that swells the subglottis and upper trachea, causing a barking cough and noisy breathing in.
• Vocal fold nodules, polyps, cysts and granulomas: benign growths on the vocal folds that keep them from closing evenly, leading to a rough or breathy voice.
• Laryngeal cancer: most often squamous cell carcinoma of the lining, strongly linked to smoking and heavy alcohol use. It may cause lasting hoarseness, a persistent cough or sore throat, painful swallowing, a lump in the neck and ear pain.
• Vocal fold paralysis: loss of movement of one or both vocal folds when a laryngeal nerve, most often the recurrent laryngeal nerve, is damaged.
• Laryngopharyngeal reflux (LPR): stomach contents travel up the esophagus and reach the larynx. It differs from typical heartburn and can be harder to recognize; adults may notice hoarseness, throat clearing or a bitter taste, while infants may have a chronic barking cough, pauses in breathing or feeding trouble.
• Laryngospasm: a sudden, involuntary closure of the vocal folds, often during a breath in, that briefly stops breathing and speech. Though frightening, it is usually short-lived.
• Irritable larynx syndrome: an oversensitive larynx that reacts with cough, throat tightness, a lump feeling, swallowing difficulty or episodes of laryngospasm, sometimes linked to chronic reflux or nerve changes.
• Laryngeal fracture or dislocation: injury from a hard blow to the neck, for example in a sports collision or car crash, which can threaten the airway.
• Laryngomalacia: the most common cause of noisy breathing (stridor) in newborns; soft, floppy tissue above the glottis falls inward on each breath in. Most cases improve on their own by about 18 to 24 months of age.
• Laryngeal cleft: a rare birth defect in which a gap between the larynx and esophagus lets food and liquid enter the airway, causing feeding and breathing problems.

Doctors examine the larynx by looking at it with a mirror or a thin camera (laryngoscopy), and may use imaging such as CT scans, ultrasound or X-rays, or take a small tissue sample (biopsy).