The human body requires energy to function properly. Energy is obtained from the external environment by ingesting food. The digestive system’s main function is to transfer the energy found in food by breaking it down into small accessible units (nutrients) for cells to use. Material which is unnecessary is excreted.
There are four processes that the digestive system performs to achieve its function.
- Motility: refers to the mixing and movement of food from the mouth to the anus with the help of smooth muscle that is found along the gastrointestinal tube.
- Secretion: the discharge of enzymes, water and other substances into the lumen of the digestive track by specialized tissues called exocrine glands.
- Digestion: the breakdown of food into smaller pieces or the degradation of large molecules into smaller ones.
- Absorption: the transport of nutrients in the blood or lymph to be circulated around the body.
The digestive system consists of structures along the gastrointestinal tube (mouth, oesophagus, stomach, small and large intestine) as well as accessory organs such as the salivary glands, pancreas, liver and gallbladder.