Digestive system - Class 4 Notes & Olympiad Questions

Digestion

a) When we eat food, our body needs to break it down into smaller pieces so that it can give us energy. This breaking-down process is called digestion.
b) The digestive system is responsible for the process of digestion. This process starts in the mouth and continues until it reaches the small intestine. Anything that our body cannot digest is eliminated from the body through the anus.
c) The digestive system consists of various organs that work together to break down and process our food.

Process of Digestion in the Digestive System

1. Mouth

a) The process of digestion begins in the mouth. The sharp teeth at the front help to cut the solid food into small pieces, while the flat teeth at the back grind the food.
b) When we chew, digestive juices and saliva mix with the food. These juices break down the starch or complex carbohydrates in the food into simpler sugars.
c) They also make the food soft and easy to swallow.
d) The tongue helps in mixing the saliva with the food.

2. Oesophagus

a) After the mouth, the food travels through the food pipe or oesophagus to reach the stomach

3. Stomach

a) The stomach is like a muscular bag. Inside the stomach, the food is churned and mixed with digestive juices produced by the stomach walls.
b) These juices break down the food into simple and soluble substances.
c) The digestion of proteins starts in the stomach.
d) The food is mixed and soaked in a strong chemical called hydrochloric acid in the stomach.
e) The food remains in the stomach for around 1 to 4 hours, and it becomes partly digested food mixed with stomach acid, called chyme.

4. Liver

a) The liver is an important organ that makes bile.
b) Bile helps in digesting fats in the small intestine.
c) The bile produced by the liver is stored in a small sac called the gallbladder.

5. Pancreas

a) The pancreas is another organ involved in digestion.
b) It makes special juices called digestive juices.
c) These juices help break down carbohydrates, fats, and proteins in the small intestine.

6. Small Intestine

a) After leaving the stomach, the food enters the small intestine. The small intestine is a long and curled tube inside our body.
b) It has three parts: the duodenum, jejunum, and ileum.
c) In the small intestine, special juices called intestinal juices help to digest the food.
d) The liver and pancreas also send their digestive juices to the small intestine to help with the digestion process.
e) The small intestine is where digestion is completed. The digested food is absorbed by tiny blood vessels in the walls of the small intestine. These blood vessels carry the nutrients from the digested food to different parts of the body.
f) Any food that is not digested and absorbed by the blood vessels moves into the large intestine.

7. Large Intestine

a) The large intestine is wider and shorter than the small intestine. Its job is to hold undigested food and absorb extra water from it.
b) The large intestine forms a stool or semi-solid waste.
c) The final stage of digestion happens in the rectum, where any leftover or unabsorbed food and water are stored.
d) Solid waste stays in the rectum until it is eliminated from the body through the anus.