Physiology of swallowing

Swallowing, or deglutition, is a complex process involving voluntary and involuntary actions to move food or liquid from the mouth to the stomach. It can be divided into three phases:

1. Oral Phase (Voluntary)

• The tongue pushes food or liquid backward into the pharynx.
• The soft palate rises to seal off the nasal cavity, preventing food from entering the nose.

2. Pharyngeal Phase (Involuntary)

• The epiglottis covers the opening of the larynx (windpipe) to prevent aspiration into the lungs.
• The vocal cords also close.
• The pharyngeal muscles contract, propelling the bolus downward.
• The upper esophageal sphincter relaxes, allowing the bolus to enter the esophagus.

3. Esophageal Phase (Involuntary)

• Peristalsis, a series of wave-like muscular contractions, moves the bolus down the esophagus.
• The lower esophageal sphincter relaxes to allow the bolus to enter the stomach.