| Epiglottis | |
|---|---|
 View of thelarynx from behind. The epiglottis is the structure at the top of the image. | |
| Details | |
| Precursor | Fourthpharyngeal arch[1] |
| Function | Prevent food from entering therespiratory tract |
| Identifiers | |
| Latin | epiglottis |
| Greek | ἐπιγλωττίς |
| MeSH | D004825 |
| TA98 | A06.2.07.001 |
| TA2 | 3190 |
| FMA | 55130 |
| Anatomical terminology | |
Theepiglottis (pl.:epiglottises orepiglottides) is a leaf-shaped flap in thethroat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. Duringswallowing, it closes to preventaspiration of food into the lungs, forcing the swallowed liquids or food to go along theesophagus toward the stomach instead. It is thus the valve that diverts passage to either thetrachea or the esophagus.
The epiglottis is made ofelastic cartilage covered with amucous membrane, attached to the entrance of thelarynx. It projects upwards and backwards behind thetongue and thehyoid bone.
The epiglottis may be inflamed in a condition calledepiglottitis, which is most commonly due to the vaccine-preventable bacteriumHaemophilus influenzae. Dysfunction may cause the inhalation of food, called aspiration, which may lead topneumonia orairway obstruction. The epiglottis is also an important landmark forintubation.
The epiglottis has been identified as early as Aristotle, and gets its name from being above theglottis (epi- +glottis).
.png)
The epiglottis sits at the entrance of thelarynx. It is shaped like a leaf ofpurslane and has a free upper part that rests behind the tongue, and a lower stalk (Latin:petiolus).[2] The stalk originates from the back surface of thethyroid cartilage, connected by athyroepiglottic ligament. At the sides, the stalk is connected to thearytenoid cartilages at the walls of the larynx byfolds.[2]
The epiglottis originates at the entrance of thelarynx, and is attached to the hyoid bone. From there, it projects upwards and backwards behind thetongue.[3] The space between the epiglottis and the tongue is called thevallecula.[3]
The epiglottis has two surfaces; a forward-facinganterior surface, and aposterior surface facing the larynx.[2] The forward-facing surface is covered with several layers of thin cells (stratified squamous epithelium), and isnot covered with keratin, the same surface as the back of the tongue.[2] The back surface is covered in a layer ofcolumn-shaped cells withcilia, similar to the rest of therespiratory tract. It also hasmucus-secretinggoblet cells.[2] There is an intermediate zone between these surfaces that contains cells that transition in shape.[4] The body of the epiglottis consists ofelastic cartilage.[2]
The epiglottis arises from the fourthpharyngeal arch. It can be seen as a distinct structure later than the other cartilage of the pharynx, visible around the fifth month of development.[1] The position of the epiglottis also changes with ageing. In infants, it touches thesoft palate, whereas in adults, its position is lower.[3]
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.[5] The front surface of the epiglottis is occasionally notched.[2]
The epiglottis is normally pointed upward duringbreathing with its underside functioning as part of thepharynx.[2] There aretaste buds on the epiglottis.[6]
Duringswallowing, the epiglottis bends backwards, folding over the entrance to the trachea, and preventing food from going into it.[2] The folding backwards is a complex movement the causes of which are not completely understood.[2] It is likely that during swallowing thehyoid bone and thelarynx move upwards and forwards, which increases passive pressure from the back of the tongue; thearyepiglottic muscles contract; the passive weight of the food pushes down; and the laryngeal and thyroarytenoid muscles contract.[2] The consequence of this is that during swallowing the bent epiglottis blocks off thetrachea, preventing food from going into it; food instead travels down theesophagus, which is behind it.[3]
In many languages, the epiglottis is not essential for producing sounds.[2] In some languages, the epiglottis is used to produceepiglottal consonant speech sounds, though this sound-type is rather rare.[7]
Inflammation of the epiglottis is known as epiglottitis. Epiglottitis is mainly caused byHaemophilus influenzae. A person with epiglottitis may have a fever, sore throat, difficulty swallowing, and difficulty breathing. For this reason, acute epiglottitis is considered amedical emergency, because of the risk of obstruction of the pharynx. Epiglottitis is often managed withantibiotics, inhaled aerosolisedepinephrine to act as abronchodilator, and may requiretracheal intubation or atracheostomy if breathing is difficult.[8]
The incidence of epiglottitis has decreased significantly in countries wherevaccination againstHaemophilus influenzae is administered.[9][10]
When food or other objects travel down the respiratory tract rather than down the esophagus to the stomach, this is calledaspiration. This can lead tothe obstruction of airways,inflammation of lung tissue, andaspiration pneumonia; and in the long term,atelectasis andbronchiectasis.[3] One reason aspiration can occur is because of failure of the epiglottis to close completely.[2][3]
If food or liquid enters the airway due to the epiglottis failing to close properly, throat-clearing or a cough reflex may occur to protect the respiratory system and expel material from the airway.[3][11] 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.[3][12]
The epiglottis and vallecula are important anatomical landmarks in intubation.[13] Abnormal positioning of the epiglottis is a rare cause ofobstructive sleep apnoea.[14]
The epiglottis is present inmammals,[15] including land mammals andcetaceans,[16] also as a cartilaginous structure.[17] Like in humans, it functions to prevent entry of food into the trachea during swallowing.[17] The position of the larynx is flat in mice and other rodents, as well as rabbits.[4] For this reason, because the epiglottis is located behind the soft palate in rabbits, they are obligate nose breathers,[18][19] as are mice and other rodents.[4] 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.[20][4] It is also common to see taste buds on the epiglottis in these species.[4]
The epiglottis was noted byAristotle,[15] although the epiglottis' function was first defined byVesalius in 1543.[21] The word has Greek roots.[22] The epiglottis gets its name from being above (Ancient Greek:ἐπί,romanized: epi-) theglottis (Ancient Greek:γλωττίς,romanized: glottis,lit. 'tongue').[23]
{{cite book}}: CS1 maint: location missing publisher (link)
