04 DIGESTION Learning Outcomes 1.9, 1.10, 1.11 What I Will Learn
• to describe the basic structure of the digestive system • to explain the basic functions of the digestive system
4.1
Key Words 3Enzyme 3Physical 3Chemical 3Alimentary canal 3Amylase 3Saliva
3Oesophagus 3Gastric juice 3Chyme 3Hydrochloric acid 3Diaphragm 3Abdomen
3Pepsin 3Peristalsis 3Pancreas 3Pancreatic juice 3Liver 3Gall bladder
3Bile 3Duodenum 3Villi 3Colon 3Absorption 3Faeces
Food provides the energy and nutrients that the body needs to stay alive and keep healthy.
Before the body can make use of food, the macronutrients (protein, carbohydrates and fats) must be broken down to release the individual components – this breaking-down process is called digestion.
The micronutrients (vitamins and minerals) do not need to be digested and can be used by the body as they are. Water is absorbed into the bloodstream. Fibre is not digested – it absorbs water and is used to push waste materials from the body in the form of faeces. Once nutrients have been digested, they are absorbed into the bloodstream and taken into the cells where they can be used.
During digestion, food goes through both physical (or mechanical) and chemical changes.
