Digestive System
ICSE Class 6 · Biology · Chapter 4
What this chapter covers
- Why your body needs digestion
- Organs of the digestive system and their functions
- The process of digestion
- Digestion of carbohydrates, proteins and fats
- Indigestion and healthy food habits
Key definitions
Digestion is the process by which the body breaks down large pieces of food into small, simple substances that it can absorb and use.
Saliva is the watery juice made by the salivary glands in and around the mouth.
Ingestion is the taking in of food through the mouth.
Absorption is the passing of digested food through the wall of the small intestine into the blood.
Assimilation is the use of absorbed food by the cells of the body for energy, growth and repair.
Egestion is the removal of undigested waste from the body through the anus.
Glucose is the simple sugar that is the end product of carbohydrate digestion.
Amino acids are the simple substances that are the end products of protein digestion.
Fatty acids and glycerol are the end products of fat digestion.
Indigestion is the discomfort a person feels when food is not digested properly.
Fibre is the part of plant food, such as the skins of fruit and the husk of grains, that the body cannot digest.
Key points
- Digestion breaks food into small, simple substances that the body can absorb and use.
- The alimentary canal runs from the mouth to the anus: mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus.
- The salivary glands, liver and pancreas are the main digestive glands.
- The five steps are ingestion, digestion, absorption, assimilation and egestion.
- Enzymes speed up the breaking down of food, and each enzyme acts on one kind of food.
- Starch digestion begins in the mouth, protein digestion in the stomach and fat digestion in the small intestine.
- All three are completed in the small intestine, where villi absorb the digested food.
- The end products are glucose, amino acids, and fatty acids with glycerol.
- Bile from the liver breaks fat into tiny droplets but contains no enzyme.
- The large intestine absorbs water from undigested waste.
- Eating too fast, overeating and too much oily food can cause indigestion.
- Chewing well, eating on time, drinking water, eating fibre and exercising keep the digestive system healthy.