swallowing

Swallowing, or deglutition, is the process by which a bolus of food or liquid is moved from the mouth to the stomach while protecting the airway. It relies on coordinated movements of the tongue, lips, palate, pharynx, esophagus, and larynx and is traditionally divided into oral, pharyngeal, and esophageal stages.

In the oral phase, the bolus is formed and propelled toward the oropharynx by the tongue and jaw movements. This phase is voluntary and ends as the bolus reaches the back of the throat, where the pharyngeal phase begins.

In the pharyngeal phase, the swallow becomes reflexive. The soft palate elevates to seal the nasopharynx, the larynx rises and the airway is protected by epiglottic closure, and the pharyngeal constrictors propel the bolus downward while the upper esophageal sphincter relaxes to allow entry into the esophagus. The esophageal phase follows, with peristaltic waves carrying the bolus through the esophagus into the stomach, aided by gravity for liquids.

Neural control centers in the brainstem coordinate swallowing with peripheral sensory input from the mouth and throat. Motor commands travel through cranial nerves V, VII, IX, X, and XII, enabling efficient and timely transit while minimizing aspiration risk. Swallowing changes with development, from infancy to older adulthood, and can be affected by disorders of the nervous system, muscles, or structures of the head and neck.

Dysphagia, or difficulty swallowing, is a common clinical concern that can lead to aspiration and malnutrition. Evaluation methods include videofluoroscopic swallow studies and fiberoptic endoscopic evaluation of swallowing. Management ranges from compensatory strategies and therapy to treatment of underlying conditions.