Exchange surfaces are adapted to maximise effectiveness.
An effecive echange surface allows enough of a substance to pass through it.
The size and complexity of an organism increases the difficulty of exchanging materials.
The effectiveness of an exchange surface is increased by:
- Being thin, to provide a short diffusion path
- Having a large surface area, so lots of a substance can pass through at once
- Animals have lots of blood vessels, so there is an efficeint blood supply
- Gas exchange surfaces in animals are often well ventilated
Exchange Surfaces in Humans
Gas Exchange in Humans:
- The surface are of the lungs is increased by millions of air sacs called alveoli
- The alveoli are specialised to maximise the difusion of oxygen and carbon dioxide.
- They have:
- An ernormous surface area
- A moist lining for dissolving gases
- Very thin walls
- A good blood supply
Solute Excahnge in Humans:
- The surface area of the small intestine is increased by villi.
- The villi porvides a large surface area with an extensive network of capillaries to absorb the products of digestions efficiently, by diffuision and active transport.
- They have:
- A single layer of surface cells
- A very good blood supply to assist quick absorbtion.