The larynx (), commonly called the voice box, is an
organ in the top of the
neck involved in breathing, producing sound and protecting the
trachea
The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
against food aspiration. The opening of larynx into
pharynx
The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
known as the
laryngeal inlet
The laryngeal inlet (laryngeal aditus, laryngeal aperture) is the opening that connects the pharynx and the larynx.
Borders
Its borders are formed by:
* the free curved edge of the epiglottis, anteriorly
* the arytenoid cartilages, the cornicul ...
is about 4–5 centimeters in
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...
.
The larynx houses the
vocal cords
In humans, vocal cords, also known as vocal folds or voice reeds, are folds of throat tissues that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for speec ...
, and manipulates
pitch and
volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...
, which is essential for
phonation. It is situated just below where the tract of the
pharynx
The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
splits into the trachea and the
esophagus
The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
. The word ʻlarynxʼ (plural ʻlaryngesʼ) comes from the
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
word ''lárunx'' ʻlarynx, gullet, throat.ʼ
Structure
![Larynx](https://upload.wikimedia.org/wikipedia/commons/9/9c/Larynx.svg)
The triangle-shaped larynx consists largely of cartilages that are attached to one another, and to surrounding structures, by muscles or by fibrous and elastic tissue components. The larynx is lined by a
ciliated columnar epithelium except for the vocal folds. The
cavity of the larynx extends from its triangle-shaped
inlet, to the
epiglottis
The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food in ...
, and to the circular outlet at the lower border of the
cricoid cartilage
The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
, where it is continuous with the lumen of the trachea. The mucous membrane lining the larynx forms two pairs of lateral folds that project inward into its cavity. The upper folds are called the
vestibular fold
The vestibular fold (ventricular fold, superior or false vocal cord) is one of two thick folds of mucous membrane, each enclosing a narrow band of fibrous tissue, the vestibular ligament, which is attached in front to the angle of the thyroid car ...
s. They are also sometimes called the false vocal cords for the rather obvious reason that they play no part in vocalization. The
Kargyraa
Tuvan throat singing, the main technique of which is known as ''khoomei'' ( tyv, хөөмей, xöömej, mn, хөөмий; ᠬᠦᠭᠡᠮᠡᠢ, khöömii, russian: хоомей, Chinese: 呼麦, pinyin: ''hūmài''), includes a type of overto ...
style of
Tuvan throat singing
Tuvan throat singing, the main technique of which is known as ''khoomei'' ( tyv, хөөмей, xöömej, mn, хөөмий; ᠬᠦᠭᠡᠮᠡᠢ, khöömii, russian: хоомей, Chinese: 呼麦, pinyin: ''hūmài''), includes a type of overt ...
makes use of these folds to sing an octave lower, and they are used in
Umngqokolo, a type of Xhosa throat singing. The lower pair of folds are known as the vocal cords, which produce sounds needed for speech and other vocalizations. The slit-like space between the left and right vocal cords, called the rima glottidis, is the narrowest part of the larynx. The vocal cords and the rima glottidis are together designated as the glottis. The laryngeal cavity above the vestibular folds is called the vestibule. The very middle portion of the cavity between the vestibular folds and the vocal cords is the ventricle of the larynx, or laryngeal ventricle. The infraglottic cavity is the open space below the glottis.
Location
In adult humans, the larynx is found in the
anterior neck at the level of the
cervical vertebrae C3–C6. It connects the inferior part of the
pharynx
The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
(hypopharynx) with the
trachea
The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
. The laryngeal
skeleton consists of nine
cartilages: three single (
epiglottic,
thyroid
The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...
and
cricoid
The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment sit ...
) and three paired (
arytenoid,
corniculate, and
cuneiform
Cuneiform is a logo-syllabic script that was used to write several languages of the Ancient Middle East. The script was in active use from the early Bronze Age until the beginning of the Common Era. It is named for the characteristic wedge-sh ...
).
The
hyoid bone is not part of the larynx, though the larynx is suspended from the hyoid. The larynx extends vertically from the tip of the
epiglottis
The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food in ...
to the inferior border of the
cricoid cartilage
The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
. Its interior can be divided in supraglottis,
glottis and
subglottis
The subglottis or subglottic region is the lower portion of the larynx, extending from just beneath the vocal cords down to the top of the trachea. .
Cartilages
There are nine cartilages, three unpaired and three paired (3 pairs=6), that support the mammalian larynx and form its 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 completely encircle the larynx (only the cricoid cartilage ...
: This forms the
Adam's apple (also called the laryngeal prominence). It is usually larger in males than in females. The
thyrohyoid membrane
The thyrohyoid membrane (or hyothyroid membrane) is a broad, fibro-elastic sheet of the larynx. It connects the upper border of the thyroid cartilage to the hyoid bone.
Structure
The thyrohyoid membrane is attached below to the upper border of ...
is a ligament associated with the thyroid cartilage that connects it with the hyoid bone. It supports the front portion of the larynx.
*
Cricoid cartilage
The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
: A ring of hyaline cartilage that forms the inferior wall of the larynx. It is attached to the top of the trachea. The
median cricothyroid ligament
The cricothyroid ligament (also known as the cricothyroid membrane or cricovocal membrane) is a ligament in the neck. It connects the cricoid cartilage to the thyroid cartilage. It prevents these cartilages from moving too far apart. It is cut dur ...
connects the cricoid cartilage to the thyroid cartilage.
*
Epiglottis
The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food in ...
: A large, spoon-shaped piece of elastic cartilage. During
swallowing, the pharynx and larynx rise. Elevation of the pharynx widens it to receive food and drink; elevation of the larynx causes the epiglottis to move down and form a lid over the glottis, closing it off.
Paired cartilages:
*
Arytenoid cartilages: Of the paired cartilages, the arytenoid cartilages are the most important because they influence the position and tension of the
vocal cords
In humans, vocal cords, also known as vocal folds or voice reeds, are folds of throat tissues that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for speec ...
. These are triangular pieces of mostly hyaline cartilage located at the posterosuperior border of the cricoid cartilage.
*
Corniculate cartilages
The corniculate cartilages (cartilages of Santorini) are two small conical nodules consisting of elastic cartilage, which articulate with the summits of the arytenoid cartilages and serve to prolong them posteriorly and medially.
They are situate ...
: Horn-shaped pieces of elastic cartilage located at the apex of each arytenoid cartilage.
*
Cuneiform cartilages
In the human larynx, the cuneiform cartilages (from Latin: ''cunei'', "wedge-shaped"; also known as cartilages of Wrisberg) are two small, elongated pieces of yellow elastic cartilage, placed one on either side, in the aryepiglottic fold.
The cu ...
: Club-shaped pieces of elastic cartilage located anterior to the corniculate cartilages.
Muscles
The muscles of the larynx are divided into ''intrinsic'' and ''extrinsic'' muscles. The extrinsic muscles act on the region and pass between the larynx and parts around it but have their origin elsewhere; the intrinsic muscles are confined entirely within the larynx and have their origin and insertion there.
The intrinsic muscles are divided into respiratory and the phonatory muscles (the muscles of
phonation). The respiratory muscles move the
vocal cord
In humans, vocal cords, also known as vocal folds or voice reeds, are folds of throat tissues that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for speec ...
s apart and serve breathing. The phonatory muscles move the vocal cords together and serve the production of voice. The main respiratory muscles are the
posterior cricoarytenoid muscle
The posterior cricoarytenoid muscles are small, paired intrinsic muscles of the larynx that extend between cricoid cartilage to the arytenoid cartilages in the larynx.
Structure Origin and insertion
The posterior cricoarytenoid originates f ...
s. The phonatory muscles are divided into adductors (
lateral cricoarytenoid muscle
The lateral cricoarytenoid (also anterior cricoarytenoid) muscles extend from the lateral cricoid cartilage to the muscular process of the arytenoid cartilage. By rotating the arytenoid cartilages medially, these muscles adduct the vocal cords an ...
s,
arytenoid muscle
The arytenoid muscle is a single muscle of the larynx. It passes from one arytenoid cartilage to the opposite arytenoid cartilage. It has oblique and transverse fibres. It is supplied by the recurrent laryngeal nerve. It approximates the arytenoi ...
s) and tensors (
cricothyroid muscle
The cricothyroid muscle is the only tensor muscle of the larynx aiding with phonation. It is innervated by the superior laryngeal nerve. Its action tilts the thyroid forward to help tense the vocal cords.
Structure
The cricothyroid muscle o ...
s,
thyroarytenoid muscle
The thyroarytenoid muscle is a broad, thin muscle that forms the body of the vocal fold and that supports the wall of the ventricle and its appendix. It functions to shorten the vocal folds.
Structure
It arises in front from the lower half of the ...
s).
Intrinsic
The intrinsic laryngeal muscles are responsible for controlling sound production.
*
Cricothyroid muscle
The cricothyroid muscle is the only tensor muscle of the larynx aiding with phonation. It is innervated by the superior laryngeal nerve. Its action tilts the thyroid forward to help tense the vocal cords.
Structure
The cricothyroid muscle o ...
lengthen and tense the vocal cords.
*
Posterior cricoarytenoid muscle
The posterior cricoarytenoid muscles are small, paired intrinsic muscles of the larynx that extend between cricoid cartilage to the arytenoid cartilages in the larynx.
Structure Origin and insertion
The posterior cricoarytenoid originates f ...
s abduct and externally rotate the arytenoid cartilages, resulting in abducted vocal cords.
*
Lateral cricoarytenoid muscle
The lateral cricoarytenoid (also anterior cricoarytenoid) muscles extend from the lateral cricoid cartilage to the muscular process of the arytenoid cartilage. By rotating the arytenoid cartilages medially, these muscles adduct the vocal cords an ...
s adduct and internally rotate the arytenoid cartilages, increase medial compression.
*
Transverse arytenoid muscle
The arytenoid muscle is a single muscle of the larynx. It passes from one arytenoid cartilage to the opposite arytenoid cartilage. It has oblique and transverse fibres. It is supplied by the recurrent laryngeal nerve. It approximates the aryteno ...
adduct the arytenoid cartilages, resulting in adducted vocal cords.
*
Oblique arytenoid muscle
The oblique arytenoid, the more superficial arytenoid muscle, forms two fasciculi, which pass from the base of one cartilage to the apex of the opposite one, and therefore cross each other like the limbs of the letter X; a few fibers are continued ...
s narrow the
laryngeal inlet
The laryngeal inlet (laryngeal aditus, laryngeal aperture) is the opening that connects the pharynx and the larynx.
Borders
Its borders are formed by:
* the free curved edge of the epiglottis, anteriorly
* the arytenoid cartilages, the cornicul ...
by constricting the distance between the arytenoid cartilages.
*
Thyroarytenoid muscle
The thyroarytenoid muscle is a broad, thin muscle that forms the body of the vocal fold and that supports the wall of the ventricle and its appendix. It functions to shorten the vocal folds.
Structure
It arises in front from the lower half of the ...
s narrow the laryngeal inlet, shortening the vocal cords, and lowering voice pitch. The internal thyroarytenoid is the portion of the thyroarytenoid that vibrates to produce sound.
Notably the only muscle capable of separating the vocal cords for normal breathing is the posterior cricoarytenoid. If this muscle is incapacitated on both sides, the inability to pull the vocal cords apart (abduct) will cause difficulty breathing. Bilateral injury to the recurrent laryngeal nerve would cause this condition. It is also worth noting that all muscles are innervated by the recurrent laryngeal branch of the vagus except the cricothyroid muscle, which is innervated by the external laryngeal branch of the superior laryngeal nerve (a branch of the vagus).
Additionally, intrinsic laryngeal muscles present a constitutive
Ca2+-buffering profile that predicts their better ability to handle calcium changes in comparison to other muscles.
This profile is in agreement with their function as very fast muscles with a well-developed capacity for prolonged work. Studies suggests that mechanisms involved in the prompt sequestering of Ca
2+ (sarcoplasmic reticulum Ca
2+-reuptake proteins, plasma membrane pumps, and cytosolic Ca
2+-buffering proteins) are particularly elevated in laryngeal muscles, indicating their importance for the myofiber function and protection against disease, such as
Duchenne muscular dystrophy
Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis follow ...
.
Furthermore, different levels of Orai1 in rat intrinsic laryngeal muscles and
extraocular muscle
The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the oth ...
s over the limb muscle suggests a role for store operated
calcium entry channels in those muscles' functional properties and signaling mechanisms.
Extrinsic
The extrinsic laryngeal muscles support and position the larynx within the mid-cervical cereal region.
Extrinsic laryngeal muscles
*
Sternothyroid muscle
The sternothyroid muscle, or sternothyroideus, is an infrahyoid muscle in the neck. It acts to depress the hyoid bone. It is below the sternohyoid muscle. It is shorter and wider than the sternohyoid.
Structure
The sternothyroid arises from the ...
s depress the larynx. (Innervated by ansa cervicalis)
*
Omohyoid muscles depress the larynx. (Ansa cervicalis)
*
Sternohyoid muscle
The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone.
Structure
The sternohyo ...
s depress the larynx. (Ansa cervicalis)
*
Inferior constrictor muscle
The inferior pharyngeal constrictor muscle is a skeletal muscle of the neck. It is the thickest of the three outer pharyngeal muscles. It arises from the sides of the cricoid cartilage and the thyroid cartilage. It is supplied by the vagus nerve ...
s. (CN X)
*
Thyrohyoid muscle
The thyrohyoid muscle is a small skeletal muscle on the neck. It originates from the lamina of the thyroid cartilage, and inserts into the greater cornu of the hyoid bone. It is supplied by the hypoglossal nerve, and a branch of the ventral rami o ...
s elevates the larynx. (C1)
*
Digastric
The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle belli ...
elevates the larynx. (CN V
3, CN VII)
*
Stylohyoid
The stylohyoid muscle is a slender muscle, lying anterior and superior of the posterior belly of the digastric muscle. It is one of the suprahyoid muscles. It shares this muscle's innervation by the facial nerve, and functions to draw the hyoid ...
elevates the larynx. (CN VII)
*
Mylohyoid elevates the larynx. (CN V
3)
*
Geniohyoid
The geniohyoid muscle is a narrow muscle situated superior to the medial border of the mylohyoid muscle. It is named for its passage from the chin ("genio-" is a standard prefix for "chin") to the hyoid bone.
Structure
It arises from the inf ...
elevates the larynx. (C1)
*
Hyoglossus
The hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the styloglossus and the inf ...
elevates the larynx. (CN XII)
*
Genioglossus
The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue.
Structure
Genioglossus is the fan-shaped extrinsic tongue muscle that forms the ma ...
elevates the larynx. (CN XII)
Nerve supply
The larynx is
innervated by branches of the
vagus nerve
The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and righ ...
on each side. Sensory innervation to the glottis and laryngeal vestibule is by the internal branch of the
superior laryngeal nerve
The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of vagus nerve and in its course receives a branch from the superior cervical ganglion of the sympathetic nervous system.
The superi ...
. The external branch of the superior laryngeal nerve innervates the
cricothyroid muscle
The cricothyroid muscle is the only tensor muscle of the larynx aiding with phonation. It is innervated by the superior laryngeal nerve. Its action tilts the thyroid forward to help tense the vocal cords.
Structure
The cricothyroid muscle o ...
. Motor innervation to all other muscles of the larynx and sensory innervation to the subglottis is by the
recurrent laryngeal nerve
The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve ( cranial nerve X) that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles. There are two recurrent laryngeal nerves, right and ...
. While the sensory input described above is (general) visceral sensation (diffuse, poorly localized), the vocal cords also receives general somatic sensory innervation (proprioceptive and touch) by the superior laryngeal nerve.
Injury to the external branch of the superior laryngeal nerve causes weakened phonation because the vocal cords cannot be tightened. Injury to one of the recurrent laryngeal nerves produces
hoarseness
A hoarse voice, also known as dysphonia or hoarseness, is when the voice involuntarily sounds breathy, raspy, or strained, or is softer in volume or lower in pitch. A hoarse voice, can be associated with a feeling of unease or scratchiness in the ...
, if both are damaged the voice may or may not be preserved, but breathing becomes difficult.
Development
In newborn infants, 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.
Laryngeal cavity
The laryngeal cavity (cavity of the larynx) extends from the
laryngeal inlet
The laryngeal inlet (laryngeal aditus, laryngeal aperture) is the opening that connects the pharynx and the larynx.
Borders
Its borders are formed by:
* the free curved edge of the epiglottis, anteriorly
* the arytenoid cartilages, the cornicul ...
downwards to the lower border of the
cricoid cartilage
The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
where it is continuous with that of the
trachea
The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
.
It is divided into two parts by the projection of the
vocal fold
The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound product ...
s, between which is a narrow triangular opening, the
rima glottidis
The rima glottidis is the opening between the two true vocal cords anteriorly, and the two arytenoid cartilages posteriorly. It is part of the larynx.
Anatomy
The rima glottidis is the narrowest part of larynx. It is longer (~23 mm) in males ...
.
The portion of the cavity of the larynx above the vocal folds is called the
laryngeal vestibule; it is wide and triangular in shape, its base or anterior wall presenting, however, about its center the backward projection of the tubercle of the epiglottis.
It contains the
vestibular fold
The vestibular fold (ventricular fold, superior or false vocal cord) is one of two thick folds of mucous membrane, each enclosing a narrow band of fibrous tissue, the vestibular ligament, which is attached in front to the angle of the thyroid car ...
s, and between these and the vocal folds are the
laryngeal ventricles.
The portion below the vocal folds is called the infraglottic cavity. It is at first of an elliptical form, but lower down it widens out, assumes a circular form, and is continuous with the tube of the trachea.
Function
Sound generation
Sound is generated in the larynx, and that is where
pitch and
volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...
are manipulated. The strength of
expiration
Expiration or expiration date may refer to:
Expiration
Expiration may refer to:
*Death
*Exhalation of breath, breathing out
*Expiration (options), the legal termination of an option to take an action
*Shelf life, or the time after which a product ...
from the lungs also contributes to loudness.
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
The vocal tract is the cavity in human bodies and in animals where the sound produced at the sound source ( larynx in mammals; syrinx in birds) is filtered.
In birds it consists of the trachea, the syrinx, the oral cavity, the upper part of th ...
, configured differently based on the position of the
tongue
The tongue is a muscular organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive process, and is the primary organ of taste. The tongue's upper surface (dorsum) is covered by taste ...
,
lip
The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
s,
mouth, and
pharynx
The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
. The process of altering a source sound as it passes through the filter of the vocal tract creates the many different vowel and consonant sounds of the world's languages as well as tone, certain realizations of stress and other types of linguistic prosody. The larynx also has a similar function to the lungs in creating pressure differences required for sound production; a constricted larynx can be raised or lowered affecting the volume of the oral cavity as necessary in glottalic consonants.
The vocal cords can be held close together (by adducting the arytenoid cartilages) so that they vibrate (see
phonation). The muscles attached to the arytenoid cartilages control the degree of opening. Vocal cord length and tension can be controlled by rocking the
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 completely encircle the larynx (only the cricoid cartilage ...
forward and backward on the
cricoid cartilage
The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
(either directly by contracting the cricothyroids or indirectly by changing the vertical position of the larynx), by manipulating the tension of the muscles within the vocal cords, and by moving the arytenoids forward or backward. This causes the pitch produced during
phonation to rise or fall. In most males the vocal cords are longer and have a greater mass than most females' vocal cords, producing a lower pitch.
The vocal apparatus consists of two pairs of folds, the
vestibular fold
The vestibular fold (ventricular fold, superior or false vocal cord) is one of two thick folds of mucous membrane, each enclosing a narrow band of fibrous tissue, the vestibular ligament, which is attached in front to the angle of the thyroid car ...
s (false vocal cords) and the true
vocal cords
In humans, vocal cords, also known as vocal folds or voice reeds, are folds of throat tissues that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for speec ...
. The vestibular folds are covered by
respiratory epithelium
Respiratory epithelium, or airway epithelium, is a type of ciliated columnar epithelium found lining most of the respiratory tract as respiratory mucosa, where it serves to moisten and protect the airways. It is not present in the vocal cords o ...
, while the vocal cords are covered by
stratified squamous epithelium. The vestibular folds are not responsible for sound production, but rather for resonance. The exceptions to this are found in
Tibetan chanting and Kargyraa, a style of
Tuvan throat singing
Tuvan throat singing, the main technique of which is known as ''khoomei'' ( tyv, хөөмей, xöömej, mn, хөөмий; ᠬᠦᠭᠡᠮᠡᠢ, khöömii, russian: хоомей, Chinese: 呼麦, pinyin: ''hūmài''), includes a type of overt ...
. Both make use of the vestibular folds to create an undertone. These false vocal cords do not contain muscle, while the true vocal cords do have skeletal muscle.
Other
![Normal Epiglottis](https://upload.wikimedia.org/wikipedia/commons/d/d6/Normal_Epiglottis.jpg)
The most important role of the larynx is its protective function, the prevention of foreign objects from entering the lungs by
coughing and other reflexive actions. A cough is initiated by a deep inhalation through the vocal cords, followed by the elevation of the larynx and the tight adduction (closing) of the vocal cords. The forced expiration that follows, assisted by tissue recoil and the muscles of expiration, blows the vocal cords apart, and the high pressure expels the irritating object out of the throat. Throat clearing is less violent than coughing, but is a similar increased respiratory effort countered by the tightening of the laryngeal musculature. Both coughing and throat clearing are predictable and necessary actions because they clear the respiratory passageway, but both place the vocal cords under significant strain.
Another important role of the larynx is abdominal fixation, a kind of
Valsalva maneuver
The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air out as if blowing up a balloon. Variations of the maneuver can ...
in which the lungs are filled with air in order to stiffen the thorax so that forces applied for lifting can be translated down to the legs. This is achieved by a deep inhalation followed by the adduction of the vocal cords. Grunting while lifting heavy objects is the result of some air escaping through the adducted vocal cords ready for
phonation.
Abduction of the vocal cords is important during physical exertion. The vocal cords are separated by about during normal respiration, but this width is doubled during forced respiration.
During
swallowing, elevation of the posterior portion of the tongue levers (inverts) the epiglottis over the glottis' opening to prevent swallowed material from entering the larynx which leads to the
lungs, and provides a path for a food or liquid bolus to "slide" into the esophagus; the hyo-laryngeal complex is also pulled upwards to assist this process. Stimulation of the larynx by aspirated food or liquid produces a strong
cough
A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three ph ...
reflex to protect the lungs.
In addition, intrinsic laryngeal muscles are spared from some muscle wasting disorders, such as
Duchenne muscular dystrophy
Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis follow ...
, may facilitate the development of novel strategies for the prevention and treatment of muscle wasting in a variety of clinical scenarios. ILM have a calcium regulation system profile suggestive of a better ability to handle calcium changes in comparison to other muscles, and this may provide a mechanistic insight for their unique pathophysiological properties
Clinical significance
Disorders
![Larynx endo 3](https://upload.wikimedia.org/wikipedia/commons/d/d3/Larynx_endo_3.jpg)
There are several things that can cause a larynx to not function properly. Some symptoms are hoarseness, loss of voice, pain in the throat or ears, and breathing difficulties.
*
Acute laryngitis is the sudden inflammation and swelling of the larynx. It is caused by the common cold or by excessive shouting. It is not serious.
Chronic laryngitis
Laryngitis is inflammation of the larynx (voice box). Symptoms often include a hoarse voice and may include fever, cough, pain in the front of the neck, and trouble swallowing. Typically, these last under two weeks.
Laryngitis is categorise ...
is caused by smoking, dust, frequent yelling, or prolonged exposure to polluted air. It is much more serious than acute laryngitis.
*
Presbylarynx is a condition in which age-related atrophy of the soft tissues of the larynx results in weak voice and restricted vocal range and stamina. Bowing of the anterior portion of the vocal colds is found on laryngoscopy.
*
Ulcers
An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...
may be caused by the prolonged presence of an
endotracheal tube
A tracheal tube is a catheter that is inserted into the Vertebrate trachea, trachea for the primary purpose of establishing and maintaining a patent airway and to ensure the adequate Gas exchange, exchange of oxygen and carbon dioxide.
Many diffe ...
.
*
Polyps
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) end i ...
and
vocal cord nodule
Vocal cord nodules are bilaterally symmetrical benign white masses that form at the midpoint of the vocal folds. Although diagnosis involves a physical examination of the head and neck, as well as perceptual voice measures, visualization of the ...
s are small bumps caused by prolonged exposure to
tobacco smoke
Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C d ...
and vocal misuse, respectively.
* Two related types of
cancer of the larynx
Laryngeal cancers are mostly squamous-cell carcinomas, reflecting their origin from the epithelium of the larynx.
Cancer can develop in any part of the larynx. The prognosis is affected by the location of the tumour. For the purposes of staging ...
, namely
squamous cell carcinoma and
verrucous carcinoma
Verrucous carcinoma (VC) is an uncommon variant of squamous cell carcinoma. This form of cancer is often seen in those who chew tobacco or use snuff orally, so much so that it is sometimes referred to as "Snuff dipper's cancer".
Signs and symp ...
, are strongly associated with repeated exposure to cigarette smoke and alcohol.
*
Vocal cord paresis
Vocal cord paresis, also known as recurrent laryngeal nerve paralysis or vocal fold paralysis, is an injury to one or both recurrent laryngeal nerves (RLNs), which control all intrinsic muscles of the larynx except for the cricothyroid muscle. The ...
is weakness of one or both vocal cords that can greatly impact daily life.
* Idiopathic
laryngeal spasm
Laryngospasm is an uncontrolled or involuntary muscular contraction (spasm) of the vocal folds. The condition typically lasts less than 60 seconds, but in cases partial blocking it may last 20 to 30 minutes and hinder inspiration, while exhala ...
.
*
Laryngopharyngeal reflux
Laryngopharyngeal reflux (LPR) is the retrograde flow of gastric contents into the larynx, oropharynx and/or the nasopharynx. LPR causes respiratory symptoms such as cough and wheezing and is often associated with head and neck complaints such a ...
is a condition in which acid from the stomach irritates and burns the larynx. Similar damage can occur with
gastroesophageal reflux disease
Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases where stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/ ...
(GERD).
*
Laryngomalacia
Laryngomalacia (literally, "soft larynx") is the most common cause of chronic stridor in infancy, in which the soft, immature cartilage of the upper larynx collapses inward during inhalation, causing airway obstruction. It can also be seen in o ...
is a very common condition of infancy, in which the soft, immature cartilage of the upper larynx collapses inward during inhalation, causing airway obstruction.
*
Laryngeal perichondritis
Perichondritis is inflammation of the perichondrium, a layer of connective tissue which surrounds cartilage. A common form, auricular perichondritis (''perichondritis auriculae'') involves infection of the pinna (anatomy), pinna due to infection o ...
, the inflammation of the
perichondrium
The perichondrium (from Greek el, περί, peri, around, label=none and el, χόνδρος, chondros, cartilage, label=none) is a layer of dense irregular connective tissue that surrounds the cartilage of developing bone. It consists of two se ...
of laryngeal cartilages, causing airway obstruction.
*
Laryngeal paralysis is a condition seen in some mammals (including
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s) in which the larynx no longer opens as wide as required for the passage of air, and impedes
respiration
Respiration may refer to:
Biology
* Cellular respiration, the process in which nutrients are converted into useful energy in a cell
** Anaerobic respiration, cellular respiration without oxygen
** Maintenance respiration, the amount of cellul ...
. In mild cases it can lead to exaggerated or "raspy" breathing or
panting, and in serious cases can pose a considerable need for treatment.
*
Duchenne muscular dystrophy
Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis follow ...
, intrinsic laryngeal muscles (ILM) are spared from the lack of
dystrophin
Dystrophin is a rod-shaped cytoplasmic protein, and a vital part of a protein complex that connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane. This complex is variously known as the cost ...
and may serve as a useful model to study the mechanisms of muscle sparing in
neuromuscular disease
A neuromuscular disease is any disease affecting the peripheral nervous system (PNS), the neuromuscular junction, or skeletal muscle, all of which are components of the motor unit. Damage to any of these structures can cause muscle atrophy and wea ...
s.
Dystrophic ILM presented a significant increase in the expression of
calcium-binding proteins Calcium-binding proteins are proteins that participate in calcium cell signalling pathways by binding to Ca2+, the calcium ion that plays an important role in many cellular processes. Calcium-binding proteins have specific domains that bind to cal ...
. The increase of calcium-binding proteins in dystrophic ILM may permit better maintenance of calcium homeostasis, with the consequent absence of
myonecrosis
Gas gangrene (also known as clostridial myonecrosis and myonecrosis) is a bacterial infection that produces tissue gas in gangrene. This deadly form of gangrene usually is caused by ''Clostridium perfringens'' bacteria. About 1,000 cases of gas g ...
. The results further support the concept that abnormal calcium buffering is involved in these neuromuscular diseases.
Treatments
Patients who have lost the use of their larynx are typically prescribed the use of an
electrolarynx
An electrolarynx, sometimes referred to as a "throat back", is a medical device about the size of a small electric razor used to produce clearer speech by those people who have lost their voice box, usually due to cancer of the larynx. The most ...
device.
Larynx
transplants are a rare procedure.
The world's first successful operation took place in 1998 at the
Cleveland Clinic
Cleveland Clinic is a nonprofit American academic medical center based in Cleveland, Ohio. Owned and operated by the Cleveland Clinic Foundation, an Ohio nonprofit corporation established in 1921, it runs a 170-acre (69 ha) campus in Cleveland, ...
, and the second took place in October 2010 at the University of California Davis Medical Center in Sacramento.
Other animals
![Kehlkopf Pferd](https://upload.wikimedia.org/wikipedia/commons/b/b6/Kehlkopf_Pferd.jpg)
Pioneering work on the structure and evolution of the larynx was carried out in the 1920s by the British comparative anatomist
Victor Negus
Sir Victor Ewings Negus, MS, FRCS (6 February 1887 – 15 July 1974) was a British surgeon who specialised in laryngology and also made fundamental contributions to comparative anatomy with his work on the structure and evolution of the larynx ...
, culminating in his monumental work ''The Mechanism of the Larynx'' (1929). Negus, however, pointed out that the descent of the larynx reflected the reshaping and descent of the human tongue into the pharynx. This process is not complete until age six to eight years. Some researchers, such as
Philip Lieberman
Philip Lieberman (October 25, 1934 – July 12, 2022) was a cognitive scientist at Brown University, Providence, Rhode Island, United States. Originally trained in phonetics, he wrote a dissertation on intonation. His career focused on topic ...
,
Dennis Klatt,
Bart de Boer and
Kenneth Stevens using computer-modeling techniques have suggested that the species-specific human tongue allows the vocal tract (the airway above the larynx) to assume the shapes necessary to produce speech sounds that enhance the robustness of human speech. Sounds such as the vowels of the words and ,
and
(in phonetic notation), have been shown to be less subject to confusion in classic studies such as the 1950 Peterson and Barney investigation of the possibilities for computerized speech recognition.
In contrast, though other species have low larynges, their tongues remain anchored in their mouths and their vocal tracts cannot produce the range of speech sounds of humans. The ability to lower the larynx transiently in some species extends the length of their vocal tract, which as Fitch showed creates the acoustic illusion that they are larger. Research at Haskins Laboratories in the 1960s showed that speech allows humans to achieve a vocal communication rate that exceeds the fusion frequency of the auditory system by fusing sounds together into syllables and words. The additional speech sounds that the human tongue enables us to produce, particularly
allow humans to unconsciously infer the length of the vocal tract of the person who is talking, a critical element in recovering the
phoneme
In phonology and linguistics, a phoneme () is a unit of sound that can distinguish one word from another in a particular language.
For example, in most dialects of English, with the notable exception of the West Midlands and the north-wes ...
s that make up a word.
Non-mammals
Most
tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...
species possess a larynx, but its structure is typically simpler than that found in mammals. The cartilages surrounding the larynx are apparently a remnant of the original
gill arch
Branchial arches, or gill arches, are a series of bony "loops" present in fish, which support the gills. As gills are the primitive condition of vertebrates, all vertebrate embryos develop pharyngeal arches, though the eventual fate of these arc ...
es in fish, and are a common feature, but not all are always present. For example, the thyroid cartilage is found only in mammals. Similarly, only mammals possess a true
epiglottis
The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food in ...
, although a flap of non-cartilagenous
mucosa is found in a similar position in many other groups. In modern amphibians, the laryngeal skeleton is considerably reduced;
frog
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...
s have only the cricoid and arytenoid cartilages, while
salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
s possess only the arytenoids.
An example of a frog that possesses a larynx is
túngara frog
The Túngara frog (''Engystomops pustulosus'') is a species of frog in the family Leptodactylidae. It is a small nocturnal terrestrial frog found in Mexico, Central America, and the northeastern regions of South America.
The tungara frog exhib ...
. While larynx is the main sound producing organ in
túngara frog
The Túngara frog (''Engystomops pustulosus'') is a species of frog in the family Leptodactylidae. It is a small nocturnal terrestrial frog found in Mexico, Central America, and the northeastern regions of South America.
The tungara frog exhib ...
s, it serves a higher significance due to its contribution to mating call, which consist of two components: ‘whine’ and ‘chuck’.
While ‘whine’ induces female phonotaxis and allows species recognition, ‘chuck’ increases mating attractiveness.
In particular,
túngara frog
The Túngara frog (''Engystomops pustulosus'') is a species of frog in the family Leptodactylidae. It is a small nocturnal terrestrial frog found in Mexico, Central America, and the northeastern regions of South America.
The tungara frog exhib ...
produces ‘chuck’ by vibrating the fibrous mass attached to the larynx.
Vocal folds are found only in mammals, and a few
lizards. As a result, many reptiles and amphibians are essentially voiceless; frogs use ridges in the trachea to modulate sound, while
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s have a separate sound-producing organ, the
syrinx.
[
]
History
The ancient Greek physician Galen
Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
first described the larynx, describing it as the "first and supremely most important instrument of the voice".
Additional images
File:Slide14rom.JPG, Larynx. Deep dissection. Anterior view.
File:Slide36uru.JPG, Larynx. Deep dissection. Posterior view.
See also
* Articulatory phonetics
The field of articulatory phonetics is a subfield of phonetics that studies articulation and ways that humans produce speech. Articulatory phoneticians explain how humans produce speech sounds via the interaction of different physiological stru ...
* Electrolarynx
An electrolarynx, sometimes referred to as a "throat back", is a medical device about the size of a small electric razor used to produce clearer speech by those people who have lost their voice box, usually due to cancer of the larynx. The most ...
* Histology of the vocal cords
Histology is the study of the minute structure, composition, and function of tissues. Mature human vocal cords are composed of layered structures which are quite different at the histological level.
Structure
The glottis is defined as the true vo ...
* Origin of speech
References
Notes
Sources
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{{Authority control
Human head and neck
Human voice
Phonetics
Human throat
Respiratory system
Speech organs