Final answer:
In the pharyngeal phase of swallowing, there is a risk of food entering the respiratory pathways. This risk is mitigated by the closing of the epiglottis, which blocks the trachea and directs the swallowed material towards the esophagus, coinciding with deglutition apnea where breathing ceases momentarily.
Step-by-step explanation:
Bedside Swallowing Evaluation
The Bedside Swallowing Evaluation is a clinical assessment to determine if a person has difficulty swallowing (dysphagia) and to what extent this impairment affects their ability to swallow safely without aspirating food or liquids into the respiratory pathways. The process of swallowing, or deglutition, involves several stages. The pharyngeal phase is the stage of swallowing during which there is a risk of food entering respiratory pathways. This risk is blocked by the closure of the epiglottis over the tracheal opening, which prevents food from entering the airway and directs it towards the esophagus.
During the pharyngeal phase, receptors in the oropharynx send signals to the swallowing center in the medulla oblongata, initiating a sequence of involuntary actions. This includes the movement of the uvula and soft palate upward to close off the nasopharynx and the constriction of laryngeal muscles to avoid aspiration. A brief cessation of breathing, known as deglutition apnea, occurs to let the swallowing process complete without interference from respiration.