Peristalsis: Digestion is the complex process that pertains to the mechanical and chemical processes of breaking down of food molecules into smaller components that can be absorbed or assimilated. How does food move through the oesophagus to the stomach? In human beings, the food moves through the oesophagus to the stomach by a special wave-like contraction and relaxation known as Peristalsis.

The Peristaltic movement in the digestive system occurs in four different organs. These four organs are the oesophagus, the stomach, the small intestine, and the large intestine. In this article, we will provide detailed information on Peristalsis, peristaltic movement, oesophageal peristalsis and more. Read on to learn more.

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What is Peristalsis? Know Peristalsis Meaning

Peristalsis is a contraction and relaxation of food in the oesophagus where the food is forced to move down to the stomach. It can be referred to as successive wave-like contractions of the muscles that are involved in the food movement and in the movement of other particles in the digestive tract to other various processing organs that are located in the digestive system.

It is involuntary in function, and it is necessary for the movement of food down the stomach and bowels down the anus. This process called Peristalsis occurs in the body parts like the oesophagus, stomach, and intestines, and the waves may be short, continuous, or continual and transit within the complete length of the organs, based on their location.

Fig: Peristalsis

Peristalsis in the Digestive System

In the digestive system, the Peristaltic movement takes place in four different organs. These Four organs are the oesophagus, the stomach, the small intestine, and the large intestine.

 1. Oesophageal Peristalsis

i. Peristalsis that occurs in Oesophagus, starts at the upper portion of the food pipe or the oesophagus tube and then moves to the stomach by passing through the complete length driving all the food particles along the food pipe. One wave travels the complete length of the oesophagus tube in about nine seconds.
ii. If there are any leftover food particles in the oesophagus tube, then the second wave takes away these particles. This complete process is known as oesophageal peristalsis.
iii. The peristaltic waves will disappear after the stomach gets filled with food. The excess fats that are present in the food particles stop these peristaltic movements until it gets diluted with gastric juices.

Fig: Oesophageal Peristalsis

2. Peristalsis in the Stomach

i. After oesophageal peristalsis, the stomach receives ball-like food particles which are also known as bolus.

ii. Through stomach peristalsis, stomach muscles compress and break down the bolus even to a smaller size that is followed by a certain degree of hydrolysis process of the food particles in the body.

iii. It is usually observed that peristaltic waves start as weak contractions at the starting of the stomach and then become stronger at the distal regions or parts of the digestive system.

iv. The process of hydrolysis of food particles is assisted by an enzyme called pepsin. After the process of hydrolysis, all food particles are partially digested, and it is now known as chyme.

v. The chyme or the partially digested food will now stay in the stomach for a while until further peristaltic movement propels or moves it into the duodenum, the first part of the small intestine, for further processing.

vi. The stomach plays a very important role in the storage of food and can store up to \(4 – 5\) litres of food at a time. That is why the partially digested food will stay in the stomach for a small duration of time.

Fig: Peristalsis in Stomach

3. Intestinal Peristalsis

This Intestinal Peristalsis occurs in two organs, i.e., the small intestine and large intestine.

a. Small Intestine

i. When this chyme reaches the small intestine from the stomach, one peristaltic movement lasts only a couple of seconds and travels a few centimetres per second.

ii. The preliminary or the primary function of the small intestine peristaltic movement is to continue the digestion of food and absorb nutrients from the food.

iii. Once these functions are done, the chyme makes its way to the large intestine through the small intestine.

Fig: Intestinal Peristalsis in Small Intestine

b. Large Intestine

i. The peristaltic movement in the large intestine is also the same as in the small intestine.

ii. Although the large intestine has peristalsis of the type that the small intestine uses, it is not the primary propulsion.

iii. Instead, general contractions called mass movements occur one to three times per day in the large intestine, propelling the chyme (now faecal matter) toward the rectum.

Fig: Intestinal Peristalsis in Large Intestine

Peristalsis in Urinary System

Urine is also moved along through the body with the help of peristaltic movement. Two tubes in the urinary tract known as ureters use peristalsis to move liquid from the kidneys to the bladder. This liquid then leaves the body through the urethra as urine.

Disorders Associated with Peristalsis

Some of the disorders caused by improper functioning of peristalsis are as follows:

1. Gastroesophageal Reflux Disease (GERD)

I. Gastroesophageal reflux disease (GERD) is mild acid reflux that occurs when stomach acid frequently flows back into the oesophagus, and this can irritate the lining of the oesophagus.
II. In this disease, the ring of muscle between the oesophagus and stomach, also called the lower oesophageal sphincter (LES), is affected.

2. Hirschsprung Disease

I. In Hirschsprung disease, the Enteric Nervous System (ENS) is non-functional and leads to intestinal blockage.
II. The ENS controls motility, and a lack of this system will affect peristalsis where it can no longer function properly, and the food contents cannot pass through further.
III. Both the submucosal plexus and myenteric plexus are then affected.

3. Dysphagia

In dysphagia, the peristalsis in the oesophagus is affected, and people with this condition have difficulty in swallowing food, and thus it means that it takes more time and effort to move food or liquid from mouth to stomach.

4. Oesophageal spasms

I. There are a few distinct forms of disorders that can cause spasms of the muscles in the oesophagus.
II. Spasms can be intermittent and/or severe and may result in regurgitation of food.

5. Reverse Peristalsis

I. This type of peristalsis is a wave of intestinal contraction that takes place in the opposite direction of the normal wave in which food present in the tube is driven in the backward or reverse direction. Hence, it is known as reverse peristalsis or anti-peristalsis, or retro peristalsis.
II. It is the converse of the contractions of the smooth muscles, which are involuntary in function and appears as a precursor to the action of vomiting. Irritation of the stomach, in particular, food poisoning, activates the emetic centre of the brain, which in response triggers an immediate vomiting reflex.

Functions of Peristalsis

Some of the functions of Peristalsis are as follows:

i. The peristaltic movement pushes the food down the oesophagus and into the stomach.
ii. In the stomach, the peristaltic movement helps in storing food and breaking down the food particles and mixing them with gastric juices that are secreted from the stomach lining. It also functions in the partial digestion process of food that is known as chyme.
iii. In the small intestine, the peristaltic movement pushes the partially digested food from the stomach to the small intestine and helps in the digestion process. It also helps in absorbing nutrients from the digested food into the bloodstream.
iv. Complete digestion is carried out in the small intestine.
v. In the large intestine, the peristaltic movement helps in moving the bodily waste along with the organ via the colon and into the rectum, and finally, this is expelled out of the body through the anus.

Do You Know!

The peristaltic movement is also seen in cattle like cows! Yes, in cud-chewing animals like cattle, camels, sheep, and also giraffes, they can always be seen chewing. In these animals, reverse peristalsis happens such that the food is brought back to the mouth for chewing.

Fig: Peristalsis in Cattle

Summary

Peristalsis is a series of involuntary wave-like muscle contractions that help in the movement of food along the digestive tract. Through this article, we understood that peristalsis plays a very important role in the digestion of food in animals and also in human beings. It also occurs in a reverse pattern in cattle like cows, buffaloes, etc. The peristalsis process starts from the oesophagus, i.e., the food pipe, and ends at the anus through the stomach, the small intestine, and finally through the large intestine.

FAQs on Peristalsis

Q.1: What is peristalsis, and what is its function?
Ans: Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. It is important because it helps for the movement of bolus or food in the stomach.

Q.2: What are the 2 functions of peristalsis?
Ans: The two functions of peristalsis are as follows:
i. The peristaltic waves push the swallowed bolus down the oesophagus.
ii. In the stomach, peristalsis churns or mixes the swallowed food with gastric juices.

Q.3: How does peristalsis protect against intestinal infection?
Ans: Peristaltic waves are important in removing the gas from the large intestine, and it helps in controlling bacterial growth and their infections.

Q.4: What organ does peristalsis occur in?
Ans: The organs where peristalsis occurs are the oesophagus, stomach, small and large intestines.

Q.5: What happens to food during reverse peristalsis?
Ans: It usually occurs as a precursor to vomiting. In this reverse peristalsis, the food moves in the opposite direction, often from the duodenum into the stomach.

Q.6. What is dysphagia?
Ans: Dysphagia occurs when the peristalsis in the oesophagus is affected. People having dysphagia have difficulty in swallowing food and it takes more time and effort to move food or liquid from mouth to stomach.

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