Role of Epiglottis

The epiglottis is a leaf-shaped flap in the throat that stops food and water from entering the windpipe and the lungs. It remains open when breathing, enabling air into the larynx. During swallowing, it shuts to prevent aspiration of food into the lungs, pushing the ingested liquids or food to proceed up the oesophagus into the stomach instead. It is therefore the valve that diverts flow to either the trachea or the oesophagus. 

The epiglottis is formed of elastic cartilage coated with a mucous membrane, linked to the entrance of the larynx. It extends upwards and rearward behind the tongue and the hyoid bone.

The epiglottis may be inflamed in a disorder termed epiglottitis, which is most usually caused by the vaccine-preventable bacterium Haemophilus influenzae. Dysfunction may induce the inhaling of food, termed aspiration, which may lead to pneumonia or airway blockage. The epiglottis is also an essential marker during intubation. The epiglottis has been recognised as early as Aristotle, and receives its name from being above the glottis

Structure of Epiglottis

The epiglottis is made of elastic cartilage in the shape of a leaf. The stalk (petioles) is its slender base, and it is linked to the thyroid cartilage’s laryngeal prominence by an elastic ligamentous band termed the thyroepiglottic ligament. The aryepiglottic folds link the epiglottis’s lateral edges to the larynx’s arytenoid cartilages. Each fold includes the aryepiglottic muscle, which is critical for epiglottis movement. The epiglottis’s upper end is free and extends posterosuperiorly from the stalk, prior to the laryngeal intake and posterior to the hyoid bone’s body and the base of the tongue. The epiglottis has two surfaces: the lingual (anterior) surface and the laryngeal (posterior) surface (posterior). 

1. Lingual surface – The epiglottis’s lingual surface is covered by the oral cavity’s mucosa. More precisely, by the non-keratinized stratified squamous epithelium, which typically includes taste buds. The lingual surface mucosa reflects onto the lateral pharyngeal walls and the tongue’s pharyngeal surface, generating two lateral glossoepiglottic folds and a middle glossoepiglottic fold, respectively. This results in a shallow depression termed the epiglottic vallecula on either side of the median and lateral glossoepiglottic folds. The inferior portion of the epiglottis’s lingual side is posterior to the hyoid bone and thyrohyoid membrane. The pre-epiglottic gap is the space between this surface and the thyrohyoid membrane. It is filled with adipose tissue and lymphatics. The hyoepiglottic ligament links the lingual surface to the hyoid bone’s superior border.
2. Laryngeal surface – The laryngeal surface shares an epithelial layer with the respiratory system: the ciliated pseudostratified columnar epithelium. It is responsible for forming the front wall of the laryngeal vestibule

Function of Epiglottis 

The epiglottis’s job is to close the laryngeal inlet during swallowing, preventing food and liquid aspiration into the lungs. The epiglottis’s motions are governed by the tongue and hyoid bone’s passive movements, as well as by the activities of the aryepiglottic muscles.

• The tongue moves the food towards the oropharynx during the earliest stages of swallowing. The base of the tongue applies pressure on the epiglottis, bending it posteriorly.
• The suprahyoid muscles pull anterosuperiorly on the hyoid bone. The hyoid bone then pushes the epiglottis stalk in the same direction owing to its relationship to the epiglottis through the hyoepiglottic ligament. This results in the free end of the epiglottis continuing to move in the opposite direction, posteriorly toward the laryngeal intake.
• The aryepiglottic muscles, which connect to the epiglottis’s lateral edges, draw the epiglottis toward the larynx, sealing the laryngeal intake. They work in conjunction with the oblique arytenoid and transverse arytenoid muscles to accomplish this.

Glottis

The glottis, often called rima glottidis anatomically, is the gap between the vocal cords. The size of the gap varies according to the larynx’s activity. During normal breathing, the glottis is shaped like a narrow wedge; during forced respiration, it takes on a broad triangular form.

The glottis is slit-like during phonation, while the vocal cords are closed. When the vocal cords vibrate during pronunciation, the buzzing sounds of the human voice are produced.

Conclusion 

The epiglottis is a cartilaginous flap that extends forward and above the laryngeal intake, more precisely the rima glottidis (glottis). The epiglottis’s job is to block the laryngeal inlet during swallowing, therefore preventing food and fluids from entering the lungs (aspiration). This is why we cannot (and should not attempt) to speak and breathe simultaneously when swallowing. The epiglottis is connected to the thyroid cartilage and hyoid bone in the larynx. Its motions are governed by the tongue’s passive pressure as it pulls food down the throat, as well as by the aryepiglottic muscle’s contractions.