The epiglottis is a leaf-shaped flap in the
throat
In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebrae. It contains the pharynx and larynx. An important section of it is the epiglottis, separating the esophagus from the trachea (windpipe ...
that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During
swallowing
Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. Swallowing i ...
, it closes to prevent
aspiration of food into the lungs, forcing the swallowed liquids or food to go along the
oesophagus
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 ...
toward the stomach instead. It is thus the valve that diverts passage to either the
trachea
The trachea, also known as the windpipe, is a Cartilage, 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 ...
or the oesophagus.
The epiglottis is made of
elastic cartilage
Elastic cartilage, fibroelastic cartilage or yellow fibrocartilage is a type of cartilage present in the pinnae (auricles) of the ear giving it shape, provides shape for the lateral region of the external auditory meatus, medial part of the audito ...
covered with a
mucous membrane
A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
, attached to the entrance of the
larynx
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 against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...
. It projects upwards and backwards behind the
tongue
The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...
and the
hyoid bone
The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebr ...
.
The epiglottis may be inflamed in a condition called
epiglottitis
Epiglottitis is the inflammation of the epiglottis—the flap at the base of the tongue that prevents food entering the trachea (windpipe). Symptoms are usually rapid in onset and include trouble swallowing which can result in drooling, changes t ...
, which is most commonly due to the vaccine-preventable bacteria ''
Haemophilus influenzae
''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria ...
''. Dysfunction may cause the inhalation of food, called aspiration, which may lead to
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...
or
airway obstruction
Airway obstruction is a blockage of respiration in the airway that hinders the free flow of air. It can be broadly classified into being either in the upper airway (UPA) or lower airway (LOA).
Airway obstruction is a life-threatening condition ...
. The epiglottis is also an important landmark for
intubation
Intubation (sometimes entubation) is a medical procedure involving the insertion of a tube into the body. Patients are generally anesthetized beforehand. Examples include tracheal intubation, and the balloon tamponade with a Sengstaken-Blakemo ...
.
The epiglottis has been identified as early as Aristotle, and gets its name from being above the
glottis
The glottis is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing vowels and voiced consonants.
Etymology
From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γλῶττα'' (glôtta), va ...
(''
epi-'' + ''glottis'').
Structure
![Epiglottis (PSF)](https://upload.wikimedia.org/wikipedia/commons/7/7e/Epiglottis_%28PSF%29.png)
The epiglottis sits at the entrance of the
larynx
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 against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...
. It is shaped like a leaf of
purslane Purslane is a common name for several mostly unrelated plants with edible leaves and may refer to:
* Portulacaceae, a family of succulent flowering plants, and especially:
** ''Portulaca oleracea'', a species of ''Portulaca'' eaten as a leaf vegeta ...
and has a free upper part that rests behind the tongue, and a lower stalk ( la, petiolus).
The stalk originates from the back surface of 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 ...
, connected by a
thyroepiglottic ligament
The thyroepiglottic ligament is an intrinsic ligament of the larynx. It connects the stalk of the epiglottis to the angle formed by the two laminæ of the thyroid cartilage
The thyroid cartilage is the largest of the nine cartilages that make up ...
. At the sides, the stalk is connected to the
arytenoid cartilage
The arytenoid cartilages () are a pair of small three-sided pyramids which form part of the larynx. They are the site of attachment of the vocal cords. Each is pyramidal or ladle-shaped and has three surfaces, a base, and an apex. The arytenoid ...
s at the walls of the larynx by
folds.
The epiglottis originates at the entrance of the
larynx
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 against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...
, and is attached to the hyoid bone. From there, it projects upwards and backwards behind the
tongue
The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...
.
The space between the epiglottis and the tongue is called the
vallecula
Vallecula is an anatomic term for a crevice, depression, or furrow in something.Vallecula
at .
Microanatomy
The epiglottis has two surfaces; a forward-facing surface, and a surface facing the larynx.
The forward-facing surface is covered with several layers of thin cells (
stratified squamous epithelium
A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural i ...
), and is
not covered with keratin, the same surface as the back of the tongue.
The back surface is covered in a layer of
column-shaped cells with
cilia
The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...
, similar to the rest of the
respiratory tract
The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa.
Air is breathed in through the nose to th ...
. It also has
mucous
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
-secreting
goblet cells
Goblet cells are simple columnar epithelial cells that secrete gel-forming mucins, like mucin 5AC. The goblet cells mainly use the merocrine method of secretion, secreting vesicles into a duct, but may use apocrine methods, budding off their secre ...
.
There is an intermediate zone between these surfaces that contains cells that transition in shape.
The body of the epiglottis consists of
elastic cartilage
Elastic cartilage, fibroelastic cartilage or yellow fibrocartilage is a type of cartilage present in the pinnae (auricles) of the ear giving it shape, provides shape for the lateral region of the external auditory meatus, medial part of the audito ...
.
Development
The epiglottis arises from the fourth
pharyngeal arch
The pharyngeal arches, also known as visceral arches'','' are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arch ...
. It can be seen as a distinct structure later than the other cartilage of the pharynx, visible around the fifth month of development.
The position of the epiglottis also changes with ageing. In infants, it touches the
soft palate
The soft palate (also known as the velum, palatal velum, or muscular palate) is, in mammals, the soft tissue constituting the back of the roof of the mouth. The soft palate is part of the palate of the mouth; the other part is the hard palate. ...
, whereas in adults, its position is lower.
Variation
![High rising epiglottis](https://upload.wikimedia.org/wikipedia/commons/e/ec/High_rising_epiglottis.JPG)
A high-rising epiglottis is a normal anatomical variation, visible during an examination of the mouth. It does not cause any serious problem apart from maybe a mild sensation of a foreign body in the throat. It is seen more often in children than adults and does not need any medical or surgical intervention.
The front surface of the epiglottis is occasionally notched.
Function
The epiglottis is normally pointed upward during
breathing
Breathing (or ventilation) is the process of moving air into and from the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen.
All aerobic creatures need oxygen for cellular ...
with its underside functioning as 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 struc ...
.
[ There are ]taste bud
Taste buds contain the taste receptor cells, which are also known as gustatory cells. The taste receptors are located around the small structures known as lingual papillae, papillae found on the upper surface of the tongue, soft palate, upper e ...
s on the epiglottis.
Swallowing
During swallowing
Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. Swallowing i ...
, the epiglottis bends backwards, folding over the entrance to the trachea, and preventing food from going into it. The folding backwards is a complex movement the causes of which are not completely understood. It is likely that during swallowing the hyoid bone
The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebr ...
and the larynx
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 against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...
move upwards and forwards, which increases passive pressure from the back of the tongue; because the aryepiglottic muscle
The aryepiglottic muscle, or aryepiglotticus muscle is an intrinsic muscle of the larynx.
The muscle originates from the muscular process of arytenoid cartilage and inserts to the aryepiglottic fold and lateral border of epiglottis. The aryepigl ...
s contract; because of the passive weight of the food pushing down; and because of contraction of laryngeal and because of contraction of thyroarytenoid muscles. The consequence of this is that during swallowing the bent epiglottis blocks off the trachea
The trachea, also known as the windpipe, is a Cartilage, 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 ...
, preventing food from going into it; food instead travels down 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 ...
, which is behind it.
Speech sounds
In many languages, the epiglottis is not essential for producing sounds. In some languages, the epiglottis is used to produce epiglottal consonant
A pharyngeal consonant is a consonant that is articulated primarily in the pharynx. Some phoneticians distinguish upper pharyngeal consonants, or "high" pharyngeals, pronounced by retracting the root of the tongue in the mid to upper pharynx, ...
speech sounds, though this sound-type is rather rare.
Clinical significance
Inflammation
Inflammation of the epiglottis is known as epiglottitis. Epiglottitis is mainly caused by ''Haemophilus influenzae
''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria ...
''. A person with epiglottitis may have a fever, sore throat, difficulty swallowing, and difficulty breathing. For this reason, acute epiglottitis is considered a medical emergency
A medical emergency is an acute injury or illness that poses an immediate risk to a person's life or long-term health, sometimes referred to as a situation risking "life or limb". These emergencies may require assistance from another, qualified p ...
, because of the risk of obstruction of the pharynx. Epiglottitis is often managed with antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...
s, inhaled aerosolised epinephrine
Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...
to act as a bronchodilator
A bronchodilator or broncholytic (although the latter occasionally includes secretory inhibition as well) is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lun ...
, and may require tracheal intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic catheter, tube into the vertebrate trachea, trachea (windpipe) to maintain an open airway or to serve as a conduit through which to administer ce ...
or a tracheostomy
Tracheotomy (, ), or tracheostomy, is a surgical airway management procedure which consists of making an incision (cut) on the anterior aspect (front) of the neck and opening a direct airway through an incision in the Vertebrate trachea, trache ...
if breathing is difficult.
The incidence of epiglottitis has decreased significantly in countries where vaccination
Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating ...
against ''Haemophilus influenzae'' is administered.
Aspiration
When food or other objects travel down the respiratory tract rather than down the esophagus to the stomach, this is called . This can lead to airway obstruction
Airway obstruction is a blockage of respiration in the airway that hinders the free flow of air. It can be broadly classified into being either in the upper airway (UPA) or lower airway (LOA).
Airway obstruction is a life-threatening condition ...
, inflammation of lung tissue, and aspiration pneumonia
Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may inclu ...
; and in the long term, atelectasis
Atelectasis is the collapse or closure of a lung resulting in reduced or absent gas exchange. It is usually unilateral, affecting part or all of one lung. It is a condition where the alveoli are deflated down to little or no volume, as distinct ...
and bronchiectasis
Bronchiectasis is a disease in which there is permanent enlargement of parts of the bronchi, airways of the lung. Symptoms typically include a chronic cough with sputum, mucus production. Other symptoms include shortness of breath, hemoptysis, co ...
. One reason aspiration can occur is because of failure of the epiglottis to close completely.
Should food or liquid enter the airway due to the epiglottis failing to close properly, throat clearing or the cough reflex may occur to protect the respiratory system and expel material from the airway. Where there is impairment in laryngeal vestibule sensation, silent aspiration (entry of material to the airway that does not result in a cough reflex) may occur.
Other
The epiglottis and vallecula are important anatomical landmarks in intubation. Abnormal positioning of the epiglottis is a rare cause of obstructive sleep apnoea
Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial obstruction of the upper airway leading to reduced or absent breathing during sleep. These episo ...
.
Other animals
The epiglottis is present in mammals
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
, including land mammals and cetaceans
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
, also as a cartilaginous structure. Like in humans, it functions to prevent entry of food into the trachea during swallowing. The position of the larynx is flat in mice and other rodents, as well as rabbits. For this reason, because the epiglottis is located behind the soft palate in rabbits, they are obligate nose breathers, as are mice and other rodents. In rodents and mice, there is a unique pouch in front of the epiglottis, and the epiglottis is commonly injured by inhaled substances, particularly at the transition zone between the flattened and cuboidal epithelium. It is also common to see taste buds on the epiglottis in these species.
History
The epiglottis was noted by Aristotle
Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of phil ...
, although the epiglottis' function was first defined by Vesalius
Andreas Vesalius (Latinized from Andries van Wezel) () was a 16th-century anatomist, physician, and author of one of the most influential books on human anatomy, ''De Humani Corporis Fabrica Libri Septem'' (''On the fabric of the human body'' '' ...
in 1543. The word has Greek roots. The epiglottis gets its name from being above ( grc, ἐπί, translit=epi-) the glottis
The glottis is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing vowels and voiced consonants.
Etymology
From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γλῶττα'' (glôtta), va ...
( grc, γλωττίς, translit=glottis, lit=tongue).
Additional images
File:Illu larynx.jpg, Cross-section of the larynx, with structures including the epiglottis labelled.
File:Kehlkopf Pferd.jpg, Cross-section of the larynx of a horse. The epiglottis here is shown as '2'.
File:Larynx normal.jpg, Structures of the larynx as viewed during laryngoscopy
Laryngoscopy () is endoscopy of the larynx, a part of the throat. It is a medical procedure that is used to obtain a view, for example, of the vocal folds and the glottis. Laryngoscopy may be performed to facilitate tracheal intubation during ge ...
. The leaf-like epiglottis is shown as number '3'. Other structures: 1=vocal folds, 2=vestibular fold, 3=epiglottis, 4=plica aryepiglottica, 5=arytenoid cartilage, 6=sinus piriformis, 7=dorsum of the tongue
See also
* Epiglottal consonant
A pharyngeal consonant is a consonant that is articulated primarily in the pharynx. Some phoneticians distinguish upper pharyngeal consonants, or "high" pharyngeals, pronounced by retracting the root of the tongue in the mid to upper pharynx, ...
* Epiglotto-pharyngeal consonant
A pharyngeal consonant is a consonant that is articulated primarily in the pharynx. Some phoneticians distinguish upper pharyngeal consonants, or "high" pharyngeals, pronounced by retracting the root of the tongue in the mid to upper pharynx, ...
* Pharyngeal consonant
A pharyngeal consonant is a consonant that is articulated primarily in the pharynx. Some phoneticians distinguish upper pharyngeal consonants, or "high" pharyngeals, pronounced by retracting the root of the tongue in the mid to upper pharynx, ...
References
External links
* ()
Where is the Epiglottis?
at Study Sciences
{{Authority control
Digestive system
Larynx
Human throat