Peristalsis can be defined as muscular contractions that take place in the digestive tract. These contractions are also very common in organs that link the kidney to the bladder. This is an involuntary process, and it is very important.
Through peristalsis:
Peristalsis is a series of muscle relaxations and contractions that take place in the lining of the intestines. This process makes it possible for waste and food products to be pushed through the intestines. Sometimes, it is actually possible to feel these muscular contractions as they take place. This is especially common for the large intestines. Peristalsis is only possible because the human digestive system is adapted to peristaltic pumps. These are muscular devices that make use of the same technique as those used by the system to push fluids through the body.
In this process, when water or food enters the gastro-intestinal tract, the muscles in this tract relax and compress in a motion that is wave like to allow the content to pass through. For instance, when you swallow an apple, smooth muscles in the esophagus relax and contract to allow the apple to pass through. The contracted muscles allow the content to pass to the area with relaxed muscles lower in the esophagus. This continues until the food reaches the stomach. The muscles above remain contracted to prevent the food from flowing back.
For a clearer picture of this process from the esophagus to the stomach, watch this video:
Once the food has moved from the esophagus to the stomach, the stomach forces the contents through the intestines. First, the food is moved to the small intestines for digestion. This process facilitates the removal of gas from the digestive system to avoid build-up. While there are several contractions in the small intestines, the large intestines only experience two or three contractions and relaxations, which enable fecal to be excreted from the body through the anus.
What is peristalsis and what about the whole process? Watch this video for a clearer perspective on this process: