Adaptations of exchange surfaces to maximise exchange
In Having more than one cell. organisms, surfaces and body organs are specialised for exchanging materials.
The ability to maximise exchange of substances in as short a time as possible in plants and animals is increased by having:
- A large surface area to volume ratio
- The flattened shape of structures such as leaves.
- The Tiny air sacs in the lungs, where gas is exchanged during breathing. in the respiratory system.
- The Finger-like projections in the small intestine that provide a large surface area for the absorption of food. in the digestive system.
- A short distance required for diffusion to and from cells, when the cell membrane is very thin, as in
- The flattened shape of structures such as leaves.
- The walls of blood Tiny blood vessels with walls one-cell thick where exchange of materials occurs., which are one cell thick.
- The A cell that forms part of an epithelium. of alveoli in the respiratory system, and the villi in the small intestine, which are one cell thick.
Animals also have an efficient blood supply to transport molecules to and from the exchange surface which maximises the exchange. Examples of this include:
- the network of blood capillaries that surrounds each alveolus in the lungs
- the network of blood capillaries in each villus in the small intestine
Finger-like projections in the small intestine that provide a large surface area for the absorption of food. are found in the small intestine of the digestive system. They increase the surface area of the intestines to allow digested food to be efficiently absorbed into the bloodstream and delivered to cells around the body.
Villi are filled with blood capillaries, and the blood constantly moving in them means that a steep The difference in the concentration of a chemical across a membrane. is maintained. This increases the amount of dissolved, digested food that can be absorbed into the bloodstream from the small intestine.
