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.
View of the larynx from behind. The epiglottis is the structure at the top of the image.
|Precursor||Fourth pharyngeal arch|
|Function||Prevent food from entering the respiratory tract.|
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). 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.
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. The epiglottis forms a space between itself and the tongue called the vallecula.
The epiglottis has two surfaces; a forward-facing (in Estonian) surface, and a posterior surface facing the larynx. 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. 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. The body of the epiglottis consists of elastic cartilage.
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. The position of the epiglottis also changes with ageing. In infants, it touches the soft palate, whereas in adults, it position is lower.
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. The front surface of the epiglottis is occasionally notched.
During swallowing, 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 incompletely understood. 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. 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.
In many languages, the epiglottis is not essential for producing sounds. In some languages, the epiglottis is used to produce epiglottal consonant speech sounds, though this sound-type is rather rare.
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. Behind the root of the tongue is an epiglottic vallecula which is an important anatomical landmark in intubation.
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. One reason aspiration can occur is because of failure of the oesophagus 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.
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