Pharynx Anatomy and Function Explained

The pharynx is a muscular tube connecting the nasal and oral cavities to the larynx and esophagus, composed of skeletal muscle lined by mucous membrane. It divides into the nasopharynx (respiration only), oropharynx, and laryngopharynx (both digestive and respiratory functions).

The nasopharynx lies above the oral cavity and functions solely in respiration. It's bordered superiorly by adenoid tissue and communicates with the nasal cavities. The Eustachian tube opening is located on its lateral walls, connecting the middle ear to equalize pressure.

The Eustachian tube in children is shorter and more horizontal, predisposing them to middle ear infections (otitis media). Adenoids (pharyngeal tonsils) are lymphoid tissue in the nasopharynx, part of the Waldeyer's tonsillar ring. Inflammation (adenoiditis) can obstruct airways and the Eustachian tube.

The oropharynx lies behind the oral cavity, bordered by the tongue, soft palate, and laryngopharynx. Palatine tonsils are located on its lateral walls and also make up the Waldeyer's ring structure. Tonsillitis (inflamed tonsils) and pharyngitis (inflammation of the pharyngeal mucosa) are common issues.

The laryngopharynx aka hypopharynx, is the caudal part of the pharynx, with the epiglottis and upper esophageal opening lining this structure. The superior border is the oropharynx and epiglottis; the inferior border is the cricoid cartilage where it connects to the esophagus. The epiglottis prevents food from entering the trachea.

Epiglottitis, commonly caused by Haemophilus influenzae type B, involves inflammation of the epiglottis, potentially obstructing the airway. The piriform fossa, lateral to the laryngeal inlet, can trap foreign objects like bones. The structure is a continuation of the oral pharynx.

The pharynx has outer circular (constrictor muscles) and inner longitudinal muscle layers. Zenker's diverticulum is an outpouching at the laryngopharynx level, between the thyropharyngeus and cricopharyngeus muscles, causing dysphagia, halitosis, and regurgitation.

The nasopharynx functions in respiration, while the oropharynx and laryngopharynx have both digestive and respiratory roles. During swallowing, the uvula closes the posterior nares, breathing is inhibited, the epiglottis closes the larynx, and pharyngeal muscles propel the bolus to the esophagus.