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The epiglottis is a leaf-shaped flap in the throat that keeps food from entering the windpipe and the lungs. The flap is made of elastic cartilage covered with a mucous membrane, attached to the entrance of the larynx. It projects upwards and backwards behind the tongue and the hyoid bone. It stands open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration and forcing the swallowed liquids or food to go along the esophagus instead. It is thus the valve that diverts passage to either the trachea or the esophagus.

Epiglottis
Gray958.png
View of the larynx from behind. The epiglottis is the structure at the top of the image.
Details
PrecursorFourth pharyngeal arch[1]
FunctionPrevent food from entering the respiratory tract.
Identifiers
LatinEpiglottis
MeSHD004825
TAA06.2.07.001
FMA55130
Anatomical terminology

The epiglottis gets its name from being above the glottis (epi- + glottis). There are taste buds on the epiglottis.[2]

StructureEdit

The epiglottis sits at the entrance of the larynx. It is shaped like a leaf[a] and has a free upper part that rests behind the tongue, and a lower stalk (Latin: petiolus).[3] The stalk originates from the back surface of the thyroid cartilage, connected by a thyroepiglottic ligament. At the sides, the stalk is connected to the arytenoid cartilages at the walls of the larynx by folds.[3]

The epiglottis originates at the entrance of the larynx, and is attached to the hyoid bone. From there, it projects upwards and backwards behind the tongue.[4] The epiglottis forms a space between itself and the tongue called the vallecula.[4]

MicroanatomyEdit

The epiglottis has two surfaces; a forward-facing (in Estonian) surface, and a posterior surface facing the larynx.[3] The forward-facing surface is covered with several layers of thin cells (non-keratinised stratified squamous epithelium), the same surface as the back of the tongue.[3] The back surface is covered in a layer of column-shaped cells with cilia, similar to the rest of the respiratory tract. It also has mucous-secreting goblet cells.[3] The body of the epiglottis consists of elastic cartilage.[3]

DevelopmentEdit

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.[1] The position of the epiglottis also changes with ageing. In infants, it touches the soft palate, whereas in adults, it position is lower.[4]

VariationEdit

 
A high rising epiglottis

A high-rising epiglottis is a normal anatomical variation, visible during an oral examination, which does not cause any serious problem apart from 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.[3]

FunctionEdit

The epiglottis is normally pointed upward during breathing with its underside functioning as part of the pharynx.[3]

SwallowingEdit

During swallowing, the epiglottis bends backwards, folding over the entrance to the trachea, and preventing food from going into it.[3] The folding backwards is a complex movement the causes of which are incompletely understood.[3] It is likely that during swallowing the hyoid bone and the larynx move upwards and forwards, which increases passive pressure from the back of the tongue; because the ariepiglottic muscles contract; because of the passive weight of the food pushing down; and because of contraction of laryngeal and because of contraction of thyroarytenoid muscles.[3] The consequence of this is that during swallowing the bent esophagus blocks off the trachea, preventing food from going into it; food instead travels down the esophagus, which is behind it.[4]

Speech soundsEdit

In many languages, the epiglottis is not essential for producing sounds.[3] In some languages, the epiglottis is used to produce epiglottal consonant speech sounds, though this sound-type is rather rare.[6]

Clinical significanceEdit

InflammationEdit

Inflammation of the epiglottis is known as epiglottitis. Epiglottitis is mainly caused by Haemophilus influenzae. 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, because of the risk of obstruction of the pharynx. Epiglottitis is often managed with antibiotics, racemic epinephrine (a sympathomimetic bronchodilator that is delivered by aerosol), and may require tracheal intubation or a tracheostomy if breathing is difficult.[7] Behind the root of the tongue is an epiglottic vallecula which is an important anatomical landmark in intubation.

The incidence of epiglottitis has decreased significantly in countries where vaccination against Haemophilus influenzae is administered.[8][9]

AspirationEdit

When food or other objects travel down the respiratory tract rather than down the oesophagus to the stomach, this is called aspiration. This can lead to airway obstruction, inflammation of lung tissue, and aspiration pneumonia; and in the long term, atelectasis and bronchiectasis.[citation needed][4] One reason aspiration can occur is because of failure of the oesophagus to close completely.[4][3]

Should food or liquid enter the airway due to the epiglottis failing to close properly, throat clearing,[4] or the cough reflex may occur to protect the respiratory system and expel material from the airway.[10] 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.[11][4]

HistoryEdit

The epiglottis was first described by Aristotle, although the epiglottis' function was first defined by Vesalius in 1543. It also has Greek roots.[12]

Additional imagesEdit

See alsoEdit

NotesEdit

ReferencesEdit

  1. ^ a b Schoenwolf, Gary C.; et al. (2009). ""Development of the Urogenital system"". Larsen's human embryology (4th ed., Thoroughly rev. and updated. ed.). Philadelphia: Churchill Livingstone/Elsevier. p. 362. ISBN 9780443068119.
  2. ^ Jowett, Adrian; Shrestha, Rajani (November 1998). "Mucosa and taste buds of the human epiglottis". Journal of Anatomy. 193 (4): 617–618. doi:10.1046/j.1469-7580.1998.19340617.x. PMC 1467887. PMID 10029195.
  3. ^ a b c d e f g h i j k l m Standring, Susan, ed. (2016). Gray's anatomy : the anatomical basis of clinical practice (41st ed.). Philadelphia. pp. 586–8. ISBN 9780702052309. OCLC 920806541.
  4. ^ a b c d e f g h Matsuo, Koichiro; Palmer, Jeffrey B. (November 2008). "Anatomy and Physiology of Feeding and Swallowing – Normal and Abnormal". Physical medicine and rehabilitation clinics of North America. 19 (4): 691–707. doi:10.1016/j.pmr.2008.06.001. ISSN 1047-9651. PMC 2597750. PMID 18940636.
  5. ^ Petkar N, Georgalas C, Bhattacharyya A (2007). "High-rising epiglottis in children: should it cause concern?". J Am Board Fam Med. 20 (5): 495–6. doi:10.3122/jabfm.2007.05.060212. PMID 17823468.
  6. ^ Shahin, Kimary (2011), "Pharyngeals", The Blackwell Companion to Phonology, American Cancer Society, pp. 1–24, doi:10.1002/9781444335262.wbctp0025, ISBN 9781444335262, retrieved 2019-10-06
  7. ^ Nicki R. Colledge; Brian R. Walker; Stuart H. Ralston, eds. (2010). Davidson's principles and practice of medicine. illustrated by Robert Britton (21st ed.). Edinburgh: Churchill Livingstone/Elsevier. p. 681. ISBN 978-0-7020-3084-0.
  8. ^ Reilly BK, Reddy SK, Verghese ST (April 2013). "Acute epiglottitis in the era of post-Haemophilus influenzae type B (HIB) vaccine". J Anesth. 27 (2): 316–7. doi:10.1007/s00540-012-1500-9. PMID 23076559.
  9. ^ Hermansen MN, Schmidt JH, Krug AH, Larsen K, Kristensen S (April 2014). "Low incidence of children with acute epiglottis after introduction of vaccination". Dan Med J. 61 (4): A4788. PMID 24814584.
  10. ^ Widdicombe, J. (1 July 2006). "Cough: what's in a name?". European Respiratory Journal. 28 (1): 10–15. doi:10.1183/09031936.06.00096905. PMID 16816346.
  11. ^ Ramsey, Deborah; Smithard, David; Kalra, Lalit (13 December 2005). "Silent Aspiration: What Do We Know?". Dysphagia. 20 (3): 218–225. doi:10.1007/s00455-005-0018-9. PMID 16362510.
  12. ^ Lydiatt DD, Bucher GS (March 2010). "The historical Latin and etymology of selected anatomical terms of the larynx". Clin Anat. 23 (2): 131–44. doi:10.1002/ca.20912. PMID 20069644.

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