Pharynx

The pharynx (Latin: pharynx) is a muscular, funnel-shaped tube that connects the nasal and oral cavities to the larynx and the esophagus. It is a unique anatomical region where the respiratory and digestive tracts share a common passage. Accordingly, it serves both systems.

The pharynx extends from the base of the skull to the level of the sixth cervical vertebra (C6), where it continues as the esophagus. Its walls are formed by the pharyngeal constrictor muscles and the longitudinal pharyngeal muscles, which together coordinate the complex act of swallowing.

Anatomical Structure and Regions

The pharynx is divided into three regions, each with distinct structural and functional features.

Regions of the pharynx:

• Nasopharynx (upper region; epipharynx):
  • Location: posterior to the nasal cavity, at the level of the first and second cervical vertebrae (C1–C2).
  • Function: exclusively respiratory. It is lined by respiratory epithelium (ciliated pseudostratified columnar epithelium).
  • Key structures: the pharyngeal tonsil (adenoids) is located in the roof; the lateral walls contain the pharyngeal openings of the auditory (Eustachian) tubes.
• Oropharynx (middle region; mesopharynx):
  • Location: posterior to the oral cavity, extending from the soft palate to the laryngeal inlet.
  • Function: mixed (both respiratory and digestive). It is lined by non-keratinized stratified squamous epithelium, which is more resistant to mechanical stress.
  • Key structures: includes the palatine tonsils and the lingual tonsil.
• Laryngopharynx (lower region; hypopharynx):
  • Location: posterior to the larynx, extending from the level of the epiglottis to the pharyngoesophageal junction.
  • Function: predominantly digestive; it directs the bolus into the esophagus.

Functions of Pharynx

Because of its structure and location, the pharynx performs several vital functions.

Main functions:

• Respiratory: conducts air from the nasal and oral cavities to the larynx.
• Digestive: actively propels the bolus from the oral cavity into the esophagus during swallowing. During swallowing, the soft palate elevates to seal off the nasopharynx, and the epiglottis helps protect the laryngeal inlet, preventing food from entering the nasopharynx and larynx.
• Protective: Waldeyer’s ring (the tonsillar ring) provides an immunologic barrier against pathogens. In addition, the pharyngeal (gag) reflex helps protect against aspiration and foreign-body entry.
• Speech (resonance): by changing its shape and volume, the pharynx contributes to voice production as a resonating chamber, influencing vocal timbre and projection.

Clinical significance

Clinically, the pharynx is a common site of disease. The most common problems are acute and chronic inflammatory conditions, such as pharyngitis (inflammation of the pharyngeal mucosa), tonsillitis, and adenoiditis. Tonsillar hypertrophy may contribute to upper airway obstruction and may also impair middle-ear ventilation through Eustachian tube dysfunction, leading to hearing problems. In addition, the pharynx is a common site of foreign-body impaction. Malignancies in this region are most often squamous cell carcinomas, with risk closely linked to tobacco use, alcohol consumption, and HPV infection (particularly in the oropharynx).