Larynx: What is it? Structure, Location, Development, Function and Generation of Sound

It contains the vocal cords and manipulates pitch and volume, which are essential for phonation.

The larynx, commonly called the voice box, is an organ in the upper neck of tetrapods involved in breathing, producing a sound, and protecting the windpipe from aspiration of food.

It is located just below the pharyngeal tract and divides into the trachea and esophagus. The word larynx (plural larynges) comes from a similar ancient Greek word (λάρυγξ lárynx).



In adult humans, the larynx is located in the anterior part of the neck at the level of the C3-C6 vertebrae. It connects the lower part of the pharynx (hypopharynx) with the trachea. The laryngeal skeleton comprises six cartilages: three simple (epiglottic, thyroid, and cricoid) and three pairs (arytenoid, corniculate, and cuneiform).

The hyoid bone is not part of the larynx, although the larynx is suspended from the hyoid. Its interior can be divided into supraglottis, glottis, and subglottis.


There are six cartilages, three unpaired and three pairs, that support the larynx of mammals and form their skeleton.

Unpaired cartilages
Thyroid cartilage

The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx. It does not surround the larynx; only the cricoid cartilage does.


The thyroid cartilage is a hyaline cartilage structure located in front of the larynx and above the thyroid gland. Cartilage comprises two halves, which meet in the middle in a peak called the laryngeal prominence, Adam’s apple.

On the midline above, the prominence is the superior thyroid notch. A homologous notch in the lower part of the cartilage is called a lower thyroid notch.

The two halves of the cartilage that make up the outer surfaces extend obliquely to cover the sides of the trachea. The posterior border of each half articulates with the cricoid cartilage inferiorly at a joint called the cricothyroid joint.

The most posterior part of the cartilage also has two projections up and down.

The upper projection is called the upper horn (cornu), and the lower arm is reached the lower horn. The prominent horn is long and narrow, posteriorly and medially, and ends in a conical extremity, which provides attachment to the lateral thyrohyoid ligament.

The lower horn is short and thick; it is directed downwards, with a slight forward and inward inclination, and presents, on the medial side of its tip, a tiny oval articular facet for articulation with the side of the cricoid cartilage.

The entire upper border of the thyroid cartilage is attached to the hyoid bone by the thyrohyoid membrane. The thyroid cartilage is located between the vertebrae C4 to C5.

The oblique line is a line on the thyroid cartilage. It marks the upper lateral borders of the thyroid gland. Two muscles originate along the line, the thyrohyoid muscle, and the inferior pharyngeal constrictor. The sternothyroid is inserted along the line.

The cartilage movement in this joint produces a change in the tension in the vocal cords, which in turn creates variation in the voice.

The thyroid cartilage forms most of the front wall of the larynx. It protects the vocal cords, which are directly behind it.

When the angle of the thyroid cartilage changes relative to the cricoid cartilage, this changes the tone of the voice. Cartilage also serves as an accessory for various muscles.

Cricoid cartilage

The cricoid cartilage / ˌkraɪkɔɪd kɑːrtɪlɪdʒ, or simply cricoids (from the Greek krikoeides meaning “ring”) or cricoid ring, is the only complete ring of cartilage around the trachea.

It forms the back of the voice box and functions as a binding site for muscles, cartilage, and ligaments involved in opening and closing the airways and producing speech.

The cricoid cartilage is found just below the thyroid cartilage in the neck, at the level of the C6 vertebra. It is attached medially by the median cricothyroid ligament and posterolaterally to the cricothyroid joints. It is made of hyaline cartilage and can calcify or even ossify, especially in old age.

Inferior to it are the cartilage rings around the trachea (which are not continuous but rather are C-shaped with a posterior gap). The cricoid is attached to the first tracheal ring by the cricotracheal ligament, and this can be felt like a more flexible area between the firm thyroid cartilage and the firmer cricoid.

It is also anatomically related to the thyroid gland; Although the thyroid isthmus is inferior to it, the thyroid’s two lobes extend upward on either side of the cricoid until they reach the thyroid cartilage above it.

The posterior part of the cricoid is slightly wider than the anterior and lateral parts, and is called the lamina, while the anterior portion is the band; This may be the reason for the standard comparison made between the cricoid and a signet ring.

The role of the cricoid cartilage is to provide attachments for the cricothyroid muscle, the posterior cricoarytenoid muscle, and the muscles of the lateral cricoarytenoid muscle, cartilage, and ligaments that are involved in the opening and closing of the airways and the production of speech.


The epiglottis gets its name from being above the glottis (epi- + glottis); it is a large piece of elastic cartilage in the shape of a spoon or a purslane leaf, with the stem attached to the inner surface of the thyroid cartilage.

During swallowing, the pharynx and larynx rise. The epiglottis is a flap in the throat that prevents food from entering the windpipe and lungs.

It stays open during breathing, allowing air to enter the larynx. It closes to prevent aspiration during swallowing, forcing swallowed liquids or food to go down the esophagus. Therefore, the valve diverts the passage into the trachea or esophagus.

Elevation of the pharynx widens it to receive food and drink; the height of the larynx causes the epiglottis to move downward and form a lid over the glottis, closing it. It serves as part of the anterior part of the pharynx during swallowing.

The body of the epiglottis consists of elastic cartilage. The epiglottis has two surfaces, a forward-facing surface that faces the tongue and a posterior surface that meets the larynx.

The entire lingual surface and the apical portion of the laryngeal surface (as it is vulnerable to abrasion due to its relationship to the digestive tract) are covered by non-keratinized stratified squamous epithelium.

However, some parts of the laryngeal surface, related to the respiratory system, have respiratory epithelium: pseudostratified, columnar and cylindrical cells, and mucus-secreting goblet cells.

The epiglottis arises from the fourth pharyngeal arch. It can be seen as a distinct structure later than the other cartilage of the pharynx, visible around the fifth month of development.

A high-growth epiglottis is a normal anatomical variation visible during an oral exam that does not cause serious problems other than a slight foreign body sensation in the throat. It is seen more often in children than adults and does not need any medical or surgical intervention.

The epiglottis usually points upward during breathing, with its lower part functioning as part of the pharynx.

The epiglottis prevents food from entering the windpipe and instead directs it to the esophagus behind it. Ingestion with little or no aspiration of food can occur even when the epiglottis is absent (such as when it is destroyed by disease).

If food or liquid enters the trachea due to the epiglottis not closing correctly, the gag reflex is induced to protect the respiratory system.

The glossopharyngeal nerve sends fibers to the superior epiglottis that contribute to the afferent limb of the gag reflex. (The gag reflex is variable in people from a limited response to a hypersensitive reaction.)

The superior laryngeal branch of the vagus nerve sends fibers to the inferior epiglottis that contribute to the efferent limb of the cough reflex. This initiates an attempt to dislodge food or fluid from the windpipe.

In some languages, the epiglottis produces epiglottal consonant speech sounds, although this type of sound is quite rare.

Paired cartilage
Arytenoid cartilages

The arytenoid cartilages (/ ærɪtiːnɔɪd /) are a pair of small, three-sided pyramids that are part of the larynx, to which the vocal cords attach. These allow and assist in the movement of the vocal cords.

Each of them has a pyramidal or ladle-shaped shape (arytenoid comes from the Greek Prytania, which means ladle + eidos, which means body) and has three surfaces, a base and an apex. The posterior surface is triangular, smooth, concave, and gives fixation to the arytenoid and transverse muscles.

The anterolateral surface is somewhat convex and rough. In it, near the apex of the cartilage, there is a rounded elevation (colliculus) from which a ridge (crista arcuata) curves at first backward and then downwards and forwards to the vocal process.

The lower part of this crest intervenes between two depressions or foveæ, an upper one, triangular and a lower oblong shape; the latter gives attachment to the vocalis muscle.

The medial surface is narrow, smooth, and flattened, covered by a mucous membrane, and forms the lateral limit of the intercartilaginous part of the glottic rhyme. The base of each cartilage is broad, and it has a smooth concave surface for articulation with the cricoid cartilage.

Its lateral angle is called the muscular process, and its anterior tilt is called the vocal process. The apex of each cartilage is pointed, curved back and medially, and surmounted by a small conical cartilaginous nodule, the corniculate cartilage.

The arytenoid cartilage allows the vocal cords to be tightened, relaxed, or approximated. The arytenoids articulate with the superolateral parts of the cricoid cartilage lamina, forming the cricoarytenoid joints in which they can join, separate, tilt forward or backward, and rotate.

Corniculate cartilage

Horn-shaped pieces of elastic cartilage are located at the apex of each arytenoid cartilage.

The corniculate cartilages (Santorini cartilages) are two small conical nodules consisting of elastic cartilages, which articulate with the summits of the arytenoid cartilages and serve to prolong them posteriorly and medially.

They are located in the posterior parts of the aryepiglottic folds of the mucous membrane, and sometimes they fuse with the arytenoid cartilages.

It is named after Giovanni Domenico Santorini. The word “Corniculate” has the Latin root “cornu.” Cornu means trumpet-like projections. Corniculate cartilage projections look like “horns,” hence the name.

Cuneiform cartilages

Club-shaped elastic cartilage pieces are located in front of the corniculate cartilages.

In the human larynx, cuneiform cartilages (from Latin: cunei, “wedge-shaped,” also known as Wrisberg cartilages) are two small elongated pieces of yellow elastic cartilage, placed one on each side in the aryepiglottic fold.

Cuneiforms are paired cartilages that sit on top of and move with the arytenoids. They are located above and in front of the corniculate cartilages, and the presence of these two pairs of cartilages produces small protrusions on the surface of the mucous membrane.

It was covered by the aryepiglottic folds, the cuneiforms from the lateral face of the laryngeal inlet, while the corniculate form the posterior face and the epiglottis the anterior.

The function of the cuneiform cartilages is to support the vocal cords and the lateral aspects of the epiglottis. They also provide a degree of solidity to the folds in which they are embedded.


The muscles of the larynx are divided into intrinsic and extrinsic muscles. The intrinsic muscles are divided into the respiratory and phonatory muscles (the muscles of phonation). The respiratory muscles separate the vocal cords and serve the breath.

The phonatory muscles move the vocal cords together and serve for voice production. It is irrelevant, passing between the larynx and its parts, and intrinsic, wholly confined.

The leading respiratory muscles are the posterior cricoarytenoid muscles. The phonatory powers are divided into adductors (lateral cricoarytenoid muscles, arytenoid muscles) and tensors (cricothyroid muscles, thyroarytenoid muscles).


The intrinsic laryngeal muscles are responsible for controlling sound production. The cricothyroid muscle lengthens and tightens the vocal cords.

The posterior cricoarytenoid muscles abduct and externally rotate the arytenoid cartilages, resulting in abducted vocal folds. Adduction of the lateral cricoarytenoid muscles and internally rotating the arytenoid cartilages increase medial compression.

The transverse arytenoid muscle adds the arytenoid cartilages, resulting in adducted vocal folds. The oblique arytenoid muscles narrow the entrance to the larynx by restricting the distance between the arytenoid cartilages.

Notably, the posterior cricoarytenoid is the only muscle capable of separating the vocal cords for normal respiration. If this muscle is disabled on both sides, the inability to separate the vocal cords (abduction) will cause shortness of breath.

Bilateral recurrent laryngeal nerve injury could cause this condition. It is also worth noting that all muscles are innervated by the recurrent laryngeal branch of the vagus, except for the cricothyroid power, which is innervated by the external laryngeal branch of the superior laryngeal nerve (a component of the vagus).

In addition, intrinsic laryngeal muscles have a constitutive Ca2 + buffer profile that predicts their better ability to handle calcium changes than other muscles.

This profile is consistent with their function as speedy muscles with a well-developed capacity for prolonged work.

Studies suggest that the mechanisms involved in rapid Ca2 + sequestration (sarcoplasmic reticulum Ca2 + proteins – recapture, plasma membrane pumps, and cytosolic Ca2 + proteins) are particularly elevated in laryngeal muscles, indicating their importance for function—myofiber and protection against disease, such as Duchenne muscular dystrophy.

Furthermore, differential levels of the Orai1 gene in rat intrinsic laryngeal muscles and extraocular muscles on limb muscles suggest a role for store-operated calcium input channels in muscle functional properties and signaling mechanisms.


The extrinsic laryngeal muscles support and position the larynx within the mid-cervical region. [windpipe.]

  • The sternothyroid muscles lower the larynx.
  • The omohyoid muscles lower the larynx.
  • The sternohyoid muscles lower the larynx.
Inferior constrictor muscles
  • The thyrohyoid muscles elevate the larynx.
  • Digastric elevates the larynx.
  • Stylohyoid elevates the larynx.
  • The Mylohyoid elevates the larynx.
  • Geniohyoid elevates the larynx.
  • Hyoglossus elevates the larynx.
  • Genioglossus elevates the larynx.


The larynx is innervated by branches of the vagus nerve on each side. Sensory innervation of the glottis and laryngeal vestibule is by the internal component of the superior laryngeal nerve.

The external branch of the superior laryngeal nerve supplies the cricothyroid muscle. The recurrent laryngeal nerve produces motor innervation to all other powers of the larynx and sensory innervation to the subglottis.

While the sensory input described above is (generally) visceral sensation (diffuse, poorly localized), the vocal fold also receives general somatic sensory innervation (proprioceptive and tactile) by the superior laryngeal nerve.

Injury to the external laryngeal nerve causes weakened phonation because the vocal cords cannot be tightened. Injury to one of the recurrent laryngeal nerves causes hoarseness; if both are damaged, the voice may or may not be preserved, but breathing becomes difficult.


In newborns, the larynx is initially at the level of the C2-C3 vertebrae and is further forward and higher relative to its position in the adult body. The larynx descends as the child grows.


Sound generation

Sound is generated in the larynx, where tone and volume are manipulated. The force of expiration of the lungs also contributes to the book.

Manipulation of the larynx is used to generate a source sound with a particular fundamental frequency or pitch. This source sound is altered as it travels through the vocal tract, configured differently depending on the position of the tongue, lips, mouth, and pharynx.

The process of altering a source sound as it passes through the vocal tract filter creates the many different vowels and consonant sounds of the world’s languages, pitch, certain stress realizations, and other types of linguistic prosody.

The larynx also has a function similar to that of the lungs in creating the pressure differences required for sound production; a constricted larynx can be raised or lowered by affecting the volume of the oral cavity as needed in glothatatic consonants.

The vocal cords can be held together (by adduction of the arytenoid cartilages) to vibrate (see phonation). The muscles attached to the arytenoid cartilages control the degree of opening.

The length and tension of the vocal folds can be controlled by moving the thyroid cartilage back and forth over the cricoid cartilage (either directly contracting the cricothyroid or indirectly changing the vertical position of the larynx), manipulating the tension of the muscles within the vocal cords and moving the arytenoids forwards or backwards.

This causes the pitch produced during phonation to increase or decrease. In most men, the vocal cords are longer and more massive than most of the vocal cords in women, having a lower pitch.

The vocal apparatus consists of two pairs of mucosal folds. These are false vocal folds (vestibular folds) and true vocal folds (folds). The false vocal cords are covered by respiratory epithelium, while the true vocal cords are covered by stratified squamous epithelium.

The false vocal cords are not responsible for sound production but resonance. Exceptions to this are found in Tibetan Chant and Kargyraa, a style of Tuvan throat chanting.

They both use false vocal folds to create an undertone. These false vocal cords do not contain muscle, whereas the true vocal cords do have skeletal muscle.


The most crucial role of the larynx is its protective function, preventing foreign objects from entering the lungs when coughing and other thoughtful actions.

Coughing is initiated by a deep inhalation through the vocal cords, followed by elevation of the larynx and tight adduction (closure) of the vocal cords.

The forced expiration that follows, assisted by the expiratory tissue and muscles recoil, separates the vocal cords, and the high pressure pushes the irritating object out of the throat.

Throat clearance is less violent than coughing but is a similar increased respiratory effort counteracted by tightening the laryngeal musculature.

Both coughing and throat clearing are predictable and necessary actions because they clear the respiratory passage, but both put the vocal cords under significant strain.

Another essential function of the larynx is abdominal fixation, a kind of Valsalva maneuver in which the lungs are filled with air to stiffen the chest so that the forces applied to lift can be transferred to the legs.

This is accomplished by a deep inhalation followed by the adduction of the vocal folds. Grunting when lifting heavy objects results from some air escaping through the adducted vocal folds ready for phonation.

Vocal cord sequestration is significant during physical exercise. During normal breathing, the vocal cords are approximately 8 mm (0.31 in), but this width doubles during forced breathing.

During swallowing, raising the posterior portion of the tongue (inverts) the epiglottis over the glottis opening to prevent ingested material from entering the larynx leading to the lungs and providing a pathway for a liquid bolus or food they “slide” into the esophagus.

The hyo-laryngeal complex is also stretched upward to assist in this process. Stimulating the larynx by aspirated food or fluids produces a strong cough reflex to protect the lungs.

Additionally, the intrinsic laryngeal muscles are spared some muscle wasting disorders, such as Duchenne muscular dystrophy, which may facilitate the development of new strategies for preventing and treating muscle wasting in various clinical settings.

The intrinsic muscles of the larynx have a profile of the calcium regulation system that suggests a better ability to handle calcium changes than other muscles, which may provide mechanistic insight into their unique pathophysiological properties.