Corpus: Epiglottis
1. Definition
2. Anatomy
2.1. Location
The epiglottis is located at the entrance to the larynx at the level of the hyoid bone, to which it is connected by the hyoepiglottic ligament. The space between the front of the epiglottis and the tongue is called the epiglottic vallecula. The position of the epiglottis changes with age. In children, the epiglottis is narrower and longer than in adults and can still touch the soft palate. In adults, the epiglottis is significantly lower.
2.2. Structure
The epiglottis is formed by the epiglottic cartilage. It is a plate of elastic cartilage that has numerous small perforations for vessels. It tapers caudally towards the stalk of epiglottis. At its end, the stalk of epiglottis is connected to the back of the thyroid cartilage by the thyroepiglottic ligament and is padded there by a fatty body, the preepiglottic fat.
2.3. Innervation
The upper part of the epiglottic mucosa is sensitively innervated by the glossopharyngeal nerve (IX nerve) and the lower part by the vagus nerve (X nerve). These afferents can trigger the gag and cough reflex.
3. Histology
The epiglottis has two histologically different surfaces, an anterior and a posterior surface facing the larynx. The anterior surface is covered with multilayered non-keratinized squamous epithelium, in which isolated taste receptors occur, while the posterior surface is covered with respiratory epithelium with mucus-producing goblet cells. There is a narrow transition zone between the two tissue types.
4. Embryology
The epiglottis develops from tissue of the 4th and 6th gill arch ("hypobranchial bulge").
5. Function
At rest, the epiglottis is directed cranially. During the act of swallowing, it is pulled backwards over the laryngeal outlet by the movements of the tongue and laryngeal muscles, thus preventing the aspiration of food particles into the trachea. The associated movement sequence is complex and not yet (2024) fully understood. The hyoid bone and the larynx are probably moved upwards and forwards during swallowing, thereby increasing the pressure of the back of the tongue on the epiglottis.
6. Clinic
Inflammation of the epiglottis is called epiglottitis. It is usually caused by bacteria (e.g. Haemophilus influenzae) and can lead to obstruction of the airways.
During intubation, the epiglottis is adjusted by the practitioner and pulled forwards and caudally by the tip of the laryngoscope blade located in the vallecula.