We will discuss about the process of digestion and what happens to the undigested food.
Digestion starts in the mouth. The food is first broken into smaller pieces by our teeth when we chew it. The sharp teeth in front help us to bite and cut the food into smaller pieces. The back teeth are flat and help to grind the food into a paste.
The saliva is a digestive juice made by the salivary glands that mixes well with the food while chewing. This softens the food so that the food can be easily swallowed. Saliva also starts breaking down starches into simpler soluble substances. Our tongue helps to mix the food with the saliva, and to push the food into the food pipe.
From mouth digestion continues in the stomach. The food goes to the stomach through the food pipe. The stomach muscles churn the food with more digestive juices. They break down proteins and other substances into simple soluble substances. The food remains in the stomach for upto three hours.
From the stomach, the food goes into a pipe called the small intestine. Here the food is mixed with more digestive juices and breaks down further. Some of these juices are made in the small intestine. Others are made in other body organs such as the liver and pancreas. These juices complete the digestion of food.
The food is now in a simple soluble form. It is absorbed into the blood through the walls of the small intestine. The blood takes it to all the cells in the body and then the digestion is completed in the small intestine.
So, digestion starts in the mouth, continues in the stomach and is completed in the small intestine.
Undigested food is thrown out of the body. Some parts of food cannot be digested by the body. They pass into a pipe called the large intestine. Here water is absorbed from the undigested food. The solid part is thrown out of the body as waste through the openings called the anus.