The digestive system

The stages of digestion

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The tongue pushes the alimentary bolus into the pharynx. After passing through the pharynx, the alimentary bolus moves into the oesophagus. During this operation, the epiglottis lowers to close the larynx and prevent food from going into the lungs.

This mechanical operation is called swallowing. Next, the alimentary bolus goes down to the stomach thanks to the rhythmic contractions of the oesophagus known as peristaltic waves.

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The oesophagus

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DEGLUTITION

The action of swallowing food is called deglutition. The epiglottis closes to send the bolus of food toward the back of the throat, an area called the pharynx. In doing this, the epiglottis blocks the larynx, a tube leading to the lungs.

Sometimes food may get into the larynx. This is called the false passage of food or simply food going down the wrong way. At this stage in the digestive tract, the air we breathe and the food we swallow mix together.

The bolus of food then passes down the oesophagus. It moves in successive waves until it reaches the stomach. These rhythmic contractions are called peristaltic waves. The force of gravity helps these mechanical movements to move food through the digestive tract.

THE ROLE OF SALIVA

It is worth pointing out that saliva also has a role to play at this stage of digestion. It makes swallowing easier and protects the mucous membrane covering the digestive tract. Initially, swallowing is a voluntary action, meaning that we control when we swallow our food. However, once the food has reached the pharynx, the movement is a reflex, so we do not have to consciously think, “I have to lower my epiglottis to make sure food doesn’t go down the wrong way!”

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