The channel connecting the mouth and nose to the esophagus and larynx is known as the pharynx, or throat. During respiration, the pharynx transports air to and from the trachea, or windpipe, and allows the passage of swallowed solids and liquids into the esophagus, or gullet. By way of the Eustachian tube, which connects the pharynx to the middle ear cavity on either side, the pharynx also allows for equalization of air pressure on the eardrum membrane, which divides the middle ear cavity from the external ear canal. The pharynx resembles a funnel that has been flattened in shape. Although it is fixed to the nearby structures, it is free enough to allow the pharyngeal wall to glide against them during swallowing motions. The three pharyngeal constrictors, which slightly overlap one another and make up the primary musculature of the side and rear pharyngeal walls, are the main pharyngeal muscles involved in the mechanics of swallowing.
The oral pharynx, nasal pharynx, and laryngeal pharynx are the pharynx's three primary divisions. While the oral pharynx is shared by the digestive and respiratory systems, the latter two are airways. A palatine tonsil, so named because to its proximity to the palate, can be seen on either side of the aperture between the mouth cavity and the oral pharynx. Each palatine tonsil is situated between two glossopalatine arches, which are two vertical folds of mucous tissue. The soft palate divides the nasal pharynx from the oral pharynx in the image above. On the roof of the nasal pharynx, there is another set of tonsils. The pharyngeal tonsils, sometimes referred to as the adenoids, are a component of the immune system of the body. The airway is blocked when the pharyngeal tonsils swell to an abnormally large size, which frequently happens in childhood. The root of the tongue conceals the laryngeal pharynx and the lower portion of the oral pharynx.
The bolus is passed voluntarily into the pharynx during the first step of deglutition, often known as swallowing. The back half of the tongue is elevated and retracted against the hard palate, mastication stops, breathing is hindered, and the front part of the tongue is depressed and retracted. The bolus is forced from the mouth into the pharynx by this movement, which is caused by the powerful tongue muscles. The soft palate is raised up against the posterior pharyngeal wall to block the bolus from entering the nasal pharynx. The larynx slides forward and upward under the base of the tongue as the bolus is driven into the pharynx. The bolus is propelled forward when the superior pharyngeal constrictor muscles contract, starting a fast pharyngeal peristaltic contraction that proceeds down the pharynx. The lower pharynx's walls and structures are raised to engulf the approaching quantity of food. The bolus is redirected to the pharynx by the epiglottis, a lid-like covering that guards the larynx's opening. As the bolus draws near, the cricopharyngeal muscle, or upper esophageal sphincter, which has been keeping the esophagus shut up to this point, relaxes and permits the bolus to enter the upper esophagus. The major esophageal peristaltic contraction results from the continuation of the pharyngeal peristaltic contraction into the esophagus.
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