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Peristalsis: Formation of Bolus in Medical Terms

Human physiology is a mysterious one. The functions of all the organs are designed in such a way that no one will interfere with the other even when they are in the same system. One such excellent function of the gastrointestinal tract is bolus formation. The scientific term to describe this is called peristalsis. In this section, we will elaborately discuss the peristaltic movement, its anatomy, definition, and how it is executed by the digestive tracts in different locations.

What is Bolus?

The digestive tract of human physiology ranges from the mouth to the rectal end. What we eat gets digested in the path and the necessary nutrients are absorbed on the way. The function of the organs and tissues is designed and evolved accordingly. In fact, it has the ability to digest food first in an acidic environment and then convert it to alkaline chyme to do the rest of the digestion. It shows how efficiently our body produces enzymes digestive enzymes that work in the acidic and basic environment separately. To make this unique functioning possible, the digestive tract performs a brilliant movement of the consumed solid and liquid food. It is called peristalsis or bolus formation.   

In medical terms, the bolus meaning depicts peristaltic movement. As the grammatical meaning suggests, a bolus is a food ball that is chewed and swallowed. This swallowed food forms a ball-like lump that travels accordingly in the digestive tract. This ball is carried by a simple involuntary rhythmic muscular contraction in the digestive tract. After crossing the esophagus, it reaches the stomach. This function is then not seen in the gastric area.

When the semi-digested food crosses the stomach, bolus forms again in the small intestine. The alimentary bolus forms to travel in the small intestine without leaving any residue back. It also occurs due to the rhythmic contraction and relaxation of the smooth muscles present in the walls of the small intestine. The last part of the digestive function is accomplished here. The motion of the food particles in the form of the bolus is slow but continuous.

How the Peristaltic Movement Occurs?

The bolus meaning medical term suggests that the gulped masticated food particles run through the alimentary canal in the form of a ball. This ball maintains its fragile consistency with the help of the coordinated relaxation and contraction of the smooth muscles. These muscles in the alimentary canal are involuntary in nature. They are not controlled by our will. It is a reflex that our brain controls with the help of sensory neurons connected to these smooth muscles. Let us discuss the process step by step.

The food is masticated, reduced to small particles in the buccal cavity, and then swallowed. It then reaches the food canal of the esophagus. It forms an alimentary bolus or a food ball that slowly runs into the stomach. The bolus is passed down by excellently coordinated contraction and relaxation of the alimentary smooth muscles present in the walls of the tube.

Upon contraction, the bolus is pushed to the consecutive location in the canal. The muscles surrounding the bolus then relax to give space to it. They contract to push the food further. This is how the alimentary bolus is carried down to the stomach via the cardiac end guarded by a sphincter muscle.

After the first phase of digestion in the acidic medium of the stomach in presence of gastric juices, the food forms a chyme and then passed again to the small intestine via the pyloric end. The same process of peristaltic movement continues and the active ingredients are being absorbed by the villi in the internal surface of the small intestine. The bolus again experiences digestion by the small intestinal enzymes and pancreatic enzymes. The final step of digestion is completed throughout the small intestinal path.

Nutrients and water are absorbed from here to make the byproduct of digestion harder and more solid. It then reaches the large intestine and proceeds to be excreted from the rectal opening. In the large intestine also, the smooth muscles perform the same function to propagate the undigested food particles and then release them through excretion.


You have understood the bolus meaning and its anatomical function. Understand the biological process of involuntary smooth muscle action to realize how the food particles move in the alimentary canal and how it is controlled. This movement is so strong that even the slippery food particles will not come out even if the consumer is upside down. In fact, astronauts who live in gravity-less environments can also eat food without any hassle.

This proves that the muscular contraction and relaxation of the alimentary canal are responsible for the peristaltic movement of the food bolus. It is not dependent on gravity. This is how the masticated food travels from one point to the other in the alimentary canal of the digestive system experiencing stepwise digestion performed by different organs.

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FAQs on Bolus

1. What Do You Mean by Peristalsis?

The formation and movement of bolus in medical terms is called peristalsis. It is a process where the smooth muscles in the alimentary canal contract and relax in accordance with the sensory control of the brain. It is involuntary which means that we cannot control this movement. The bolus formed will slowly travel in the esophagus to reach the stomach. It will then convert into a slimy liquid called chyme. The chyme will then pass to the small intestine for the final digestion and absorption of nutrients and water.

2. What is the Prime Function of Bolus?

As per the bolus meaning medical term, it is a food ball that travels at a slow pace due to the coordinated contraction and relaxation of the smooth muscles in the alimentary canal. The coordinated movement of the food particles helps us digest food without any hassle or interruption. The alimentary canal can carry more than one bolus at a time. In fact, the undigested food particles or faeces form the bolus and move in the large intestine.