Digestion is the process of breaking down food that is ingested into products that are usable by the body. The digestive system is made up of the mouth, oesophagus, stomach, small intestine, large intestines and the pancreas. The process of digestion involves many different enzymes.
There are three main types of digestive enzymes:
- Amylases that break down starch and larger sugars into the more simple sugars such as glucose
- Proteases and peptidases that break down proteins and larger peptides into smaller peptides and amino acids
- Lipases that break down fats into fatty acids and glycerol.
Digestion begins in the mouth where the food is chewed to form a bolus - a ball-like mixutre of food and saliva. The breakdown of starch is also catalysed by salivary amylase. The bolus moves down the oesophagus (by peristalsis) and into the stomach, where it is further digested by enzymes (primarily protein-digesting enzymes), stomach acid and the mechanical action of the stomach. The digested food then moves into the small intestine where the greatest amount of digestion takes place - this is the primary site of lipid digestion. Here, digestion occurs via. enzymes (from the pancreas) and bile (from the liver), as well as by mechanical actions such as peristalsis (allowing the food and the digestive secretions to mix together). In the large intestine, digestion is all but finished and all that remains is to remove the remaining water. The waste left over from the digestive process (stool) is excreted from the body via. the rectum and the anus.
- ↑ http://www.innerbody.com/image/digeov.html
- ↑ https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works