Example s of propulsion and retropulsion
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Answer:
After the food is swallowed through the mouth, it enters into Oesophagus, and then the swallowing becomes an involuntary act. When the food enters into Oesophagus, the muscles present in its wall contract and relax alternatively producing the peristaltic movement.
The Persistalsis involves the contraction of the muscle behind the food and the relaxation of the muscle in front of the food giving rise to a thrust that pushes the food forward through the digestive canal. This peristaltic movement in the stomach has three stages, they are as follows,
01. Propulsion
The peristaltic waves move the food toward the Pylorus ( the next part of the food processing in the digestive system).
02. Grinding
The most vigorous peristaltic and mixing action occur close to the Pylorus.
03. Retropulsion
The Pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum, simultaneously forcing most of its contained material backwards into the stomach.