The Stages of Food Breakdown
- Food taken into the body goes through several different stages during its passage through the alimentary canal (the gut):
- Ingestion
- Mechanical digestion
- Chemical digestion
- Absorption
- Assimilation
- Egestion
- Absorption is the movement of small digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol)
- Absorption of small soluble molecules occurs through diffusion and sometimes active transport
- Water is absorbed (by osmosis) primarily in the small intestine, but also in the colon
- After absorption, assimilation and egestion occurs
- Assimilation is the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
- Egestion is the passing out of food that has not been digested or absorbed (as faeces) through the anus
