When we eat, our food is processed by different parts of the digestive system. Digestion is the body’s way of breaking down foods into nutrients in preparation for absorption.
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). The gastrointestinal tract is a flexible muscular tube that extends from the mouth, through the oesophagus, stomach, small intestine, large intestine, and rectum to the anus (Figure 2.1).
The gastrointestinal tract takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as faeces. Most absorption of nutrients takes place in the small intestine.
