Absorption of digested food
After food is fully digested into small, soluble molecules, these molecules must pass into the blood. This process is called absorption. Most absorption happens in the small intestine. Its inner wall is folded and covered with millions of tiny finger-like structures called villi.
Villi make absorption fast and efficient because they:
- give a very large surface area,
- have thin walls so molecules pass through easily,
- contain many blood capillaries to carry molecules away.
Key idea
Absorption is the movement of digested food from the small intestine into the blood. Villi provide a large surface area and thin walls to speed this up.
Transportation to cells
Once in the blood, digested food such as glucose and amino acids is carried by the blood to every cell in the body. Cells use these materials for energy, growth and repair. This is why a good meal makes you feel energetic afterwards.
Example
Glucose absorbed from a bowl of noodles is carried by the blood to your muscle cells, where it is used to release the energy you need to run and play.
Defecation
Not all food can be digested. Undigested material such as fibre moves into the large intestine, where water is absorbed from it. The remaining solid waste, called faeces, is stored and then removed from the body through the anus. This removal of undigested waste is called defecation.
Remember
- Absorption happens mainly in the small intestine through villi.
- Blood transports digested food to all cells.
- Defecation removes undigested waste (faeces).