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Function of the Digestive System

Updated on February 8, 2015

The Function of the digestive system is to break down food into smaller units that can be used by cells of the body. The sections below show how the digestive system is organized and how it works.

Diagram of the Digestive System
Diagram of the Digestive System | Source

What is digestion?

Digestion is the process whereby food is mechanically and chemically broken down into small components that can be easily absorbed into the blood stream.

The digestive system consists of the digestive tract and a series of organs joined together by a long twisting tube starting from the mouth to the anus. These organs all work together to break down and absorb food.

Parts and Function of the Digestive system

The digestive system is made up of the mouth, the salivary glands, pharynx, esophagus, stomach, pancreas, liver, gall bladder, duodenum, small intestine, colon, cecum, rectum and anus. This collection of organs is known as the alimentary canal.


The mouth is the beginning of the digestive system, it is also where digestion starts. Food is chewed here and broken down into smaller pieces to increase the surface area for digestion. Salivary glands secrete salivary into the mouth to break down certain types of food into smaller components for further processing and absorption down the alimentary canal.


When food is swallowed it moves from the mouth, via the Pharynx and into the esophagus. In the pharynx, the Soft plate and the Epiglottis prevent food from entering the respiratory tract. Food is directed from the pharynx to the stomach via the esophagus by means of a process of wave-like muscular contraction called peristalsis.


The stomach holds food while it is being mixed with digestive juices. Digestive juices and enzymes secreted into the stomach break down food into components that can be easily absorbed into the bloodstream. When the process in the stomach is done, the contents of the stomach are pushed into the small intestine.

Small intestine (and the Pancreas)

The small intestine is a long muscular tube in which further digestion and absorption of nutrients take place. Digestive enzymes and bile are secreted into the small intestine from the pancreas and the liver.


Function of the liver in the digestive system: The liver has many functions, but in the digestive system the liver secretes enzymes in the small intestine that break down food into smaller components that can easily be absorbed into the bloodstream. The gall bladder stores bile produced by the liver. During digestion, there are processes that would cause the gallbladder to contract and push bile into the duodenum for the digestion of fat.


The colon or the large intestine processes the waste from the digestive process. The colon is made up of the cecum, ascending, transverse and descending colon, and the rectum. Stool from the descending colon is emptied into the rectum where these will be expelled via the anus. The anus is located at the end of the digestive tract. It has specialized muscles that help hold up stool. When the time is right, these muscles relaxes to release the contents of the rectum into the toilet bowl.

Mechanical Digestion and Chemical Digestion

Function of the digestive system: Mechanical Digestion and Chemical Digestion
Function of the digestive system: Mechanical Digestion and Chemical Digestion | Source

Mechanical Digestion and Chemical Digestion

Digestion can be divided into two parts; Chemical and Mechanical digestion. These two major types of digestion function as a unit to help us get the vital nutrients we need to survive.

Mechanical digestion is the crushing, pulling, pushing and churning of food particles. This does not change the chemical composition of the food. The teeth are very important in crushing food into smaller pieces. The stomach is lined with layers of muscles which churn food to further break it down to smaller pieces.

Chemical digestion takes place in the mouth, stomach and small intestine. This type of digestion changes the chemical composition of the food by enzyme action. The brain signals for the release of these enzymes.

As the food travels through the small intestine, enzymes will be released to break down the food. The first step of chemical digestion takes place in the mouth where carbohydrate is broken down into simple sugars called monosaccharides, The type enzyme that act on carbohydrate is called salivary amylase. In the stomach protein is broken down into smaller components called amino acids. The enzyme that breaks down protein is called pepsin. Fats digestion starts in the stomach with the help of a substance called bile. But it is finally broken down into its components (called fatty acids) in the small intestine with the help of pancreatic enzymes.


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