Chapter 40: Pharynx Anatomy

Pharynx Anatomy focuses on the pharynx, a vital 12–14 centimeter long, inverted musculomembranous tube that extends from the cranial base down to the level of the cricoid cartilage, where it becomes continuous with the esophagus. Functionally and anatomically, the pharynx is divided into three regions: the nasopharynx (behind the nasal cavity), the oropharynx (behind the oral cavity), and the laryngopharynx (hypopharynx, behind the larynx). The structure is maintained by two layers of fascia—the buccopharyngeal and the pharyngobasilar fasciae—and surrounded by clinically important tissue areas, notably the retropharyngeal space and the specialized, suprahyoid parapharyngeal space. Pharyngeal movement is governed by three pairs of circular constrictor muscles and three pairs of longitudinal elevator muscles, which insert into the midline pharyngeal raphe. The muscles of the soft palate, including the levator veli palatini and the tensor veli palatini, are essential for elevating the palate to seal off the nasopharynx during swallowing, while the tensor veli palatini also helps open the pharyngotympanic tube. The lymphoid tissue of the pharynx forms Waldeyer’s ring, comprised anteriorly by the palatine tonsils (in the oropharynx) and posterosuperiorly by the pharyngeal tonsil (adenoid), which is often implicated in airway obstruction in young children. Blood flow is supplied by branches of the external carotid artery, and primary motor and sensory innervation is provided by the pharyngeal plexus. The pharyngeal stage of deglutition (swallowing) is an involuntary, critical process that requires rapid hyolaryngeal elevation to protect the airway while coordinated muscle contractions propel the food bolus downward. The inferior constrictor muscle contains the cricopharyngeus, which is the primary component maintaining the tonic closure of the upper esophageal sphincter (UES). Failure in this coordinated mechanism can lead to conditions like obstructive sleep apnoea (OSA), characterized by reduced muscle tone during sleep, or the formation of hypopharyngeal diverticula, such as Zenker’s diverticulum, which often forms at the weakness known as Killian’s triangle.