Mass Flow Transport Systems in Animals

• Mass flow is the bulk movement of materials. It is directed movement so involves some sort of force.
• Animals have evolved specialised mass flow transport systems that enable the efficient transport of nutrients and waste.
• In mass transport systems there is still some diffusion involved, but only at specific exchange sites at the start and end of the route travelled by the substances. The lungs are the exchange site of the gas exchange system.
• The mammalian circulatory system in mammals is a well-studied example of a mass transport system. The one-way flow of blood within the blood vessels carries essential nutrients and gases to all the cells of the body. The sites of exchange are the lungs and the capillaries.
• Mass transport systems help to:

  • Bring substances quickly from one exchange site to another
  • Maintain the concentration gradients at exchange sites
  • Maintain the concentration gradients between cells and their fluid surroundings
  • Ensure effective cell activity by keeping the immediate fluid environment of cells within a suitable metabolic range