Diffusion gradients exist between muscles and tissues/ working muscles. Oxygen diffuses from the blood vessels to the working muscles and carbon dioxide diffuses in the opposite direction.
Factors that contribute to the efficiency of diffusion are:
- Large surface area of alveoli
- Thin membranes
- Short distance for diffusion to take place over
The arterio - venous difference indicate the efficiency of oxygen uptake by the muscles during exercise. At rest, only 25% of oxygen is used. During exercise 80% is used.
Arterio venous difference = measurement of relative amounts of blood between arterial and venous blood.