FRANCIS LEROY & CHRIS LIPPENS, BIOCOSMOS / SCIENCE PHOTO LIBRARY FRANCIS LEROY & CHRIS LIPPENS, BIOCOSMOS / SCIENCE PHOTO LIBRARY
Swallowing mechanism. Animation showing the process of swallowing (deglutition) in humans. Muscles in the tongue, pharynx and oesophagus are involved in this process, which is divided into three phases: the oral phase, pharyngeal phase and oesophageal phase. The oral phase starts when food (green) enters the mouth. Then the tongue (start of clip) pushes the mass of food (the bolus) towards the back of the mouth and the pharynx. As the bolus descends down the throat, the uvula and soft palate move upwards to cover the nasopharynx and prevent the passage of food towards the nose and nasal cavities. At the same time, the swallowing reflex starts and propels the food towards the oesophagus and away from the lungs. A flap of tissue called the epiglottis folds down covers the larynx and prevents the food entering the trachea (airway). During this process, deglutition apnea occurs, in which breathing stops for a very short time.
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