10.1 The digestive system . . . . . . . . 99 10.2 Food . . . . . . . . . . . . . . . 99 10.3 Food and health . . . . . . . . . . 101 10.4 Structure of the human digestive system . . . . . . . . . . . . . . 104
10.5 Nutrition . . . . . . . . . . . . . 104 10.6 The mouth . . . . . . . . . . . . 105 10.7 The stomach. . . . . . . . . . . . 108 10.8 The small intestine . . . . . . . . . 109 10.9 The large intestine . . . . . . . . 111 10.10 Interactions of the digestive system 112
Why it matters
The body needs food for energy, and to grow and repair itself. The food we eat is composed of substances called nutrients. Many of these nutrients must be broken down into simpler molecules so that they can be absorbed and transported around the body in the bloodstream. It is the role of the digestive system to break down these nutrients and pass them into the bloodstream where they can be transported to every cell in the body.
10.1 The digestive system
Each meal we eat takes about 20 to 30 hours to travel through the digestive system. The digestive system consists of an approximately nine-metre long tube and the associated organs, the salivary glands, pancreas and liver. As food travels through this muscular tube it is broken down into simple molecules that can be absorbed into the bloodstream. The circulatory system transports these nutrients around the body to provide energy to every cell and to provide the building blocks for growth and repair of the body. Food that has not been digested is passed out of the body through the anus.
10.2 Food
Food is composed of one or more of these nutrients: l Carbohydrates l Proteins l Fats l Vitamins l Minerals These nutrients are the building blocks of food. Water is also a major component of food.
99
LO 4, 6 Biological World strand LO 6, 7 Nature of Science strand
