During the pharyngeal stage of swallowing, food entry into the nasopharynx and larynx is prevented primarily by elevation of the soft palate and closure of the glottis. This stage differs from the oral stage because it is:

• A Entirely voluntary and controlled by the cerebral cortex
• B Involuntary but driven by the enteric nervous system without central involvement
• C Involuntary, coordinated by the swallowing centre in the medulla, and accompanied by temporary inhibition of respiration ✓
• D Voluntary at onset but dependent on continuous cortical input until the bolus reaches the stomach

Explanation

The pharyngeal and oesophageal stages are involuntary, coordinated by the deglutition centre in the medulla and lower pons, and breathing is briefly inhibited during bolus passage through the pharynx. The oral (buccal) stage is the only voluntary stage, so option A describes the wrong stage. The enteric plexus coordinates distal gut motility but cannot orchestrate pharyngeal contraction, killing option B.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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