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.
DIFFERENCES
| PROPULSION | RETROPULSION |
|---|---|
| The process in which food is moved throughout the system and involves swallowing and peristalsis. | In Retropulsion, some of the chyme is forced back up against the walls of the stomach. |
| LEADS TO | |
| The Propulsion enables the food to mix with digestive juices. | The retropulsion leads to intense contractions and it causes backwardness of food into the stomach. |
| PROCESS | |
| Peristaltic waves move food from one part to the other. | Small amounts of chyme is pushed into duodenum and forcing most of the food back into the stomach. |
The peristalsis in the small intestine is stimulated by smooth muscles, which serves to expose food to the intestinal wall for the absorption and to move it forward. On the other side, Peristaltic wave in the large intestine includes pushing waste material into the rectum. The food chyme which is digested incompletely is sent reverse into the Oesophagus, it is called as Vomit. While Vomiting, the peristalsis occurs in reverse direction, then the partially digested food comes out along with HCl, so we feel burning sensation.
