Organ systems are specialised so that they can maximise the amount of materials exchanged over their membranes. The ways that effectiveness of an exchange surface can be increased are: Large surface area: a larger surface area means that more diffusion can occur at once. Thin membrane: this speeds up the exchange because the diffusion path is shorter so the molecules have less distance to travel. Efficient blood supply: In animals the blood system is very efficient for transporting a variety of substance around the body. Ventilation: gaseous exchange is also a very important for exchanging materials. Oxygen and carbon dioxide are able to move easily between the lungs and the blood by diffusion. Gas and solute exchange surfaces in humans have been adapted to maximise their effectiveness. The larger an organism gets and the more complicated it is which makes it harder for materials to be exchanged. Gaseous exchange is the process by which oxygen is taken in by the body for respiration and carbon dioxide, the waste product of respiration, is released. In humans the lungs are the organ used for gaseous exchange. When we breathe, air moves in and out of the body via our lungs. In the lungs, the air moves into the alveoli and oxygen diffuses into the blood stream. Carbon dioxide diffuses in the opposite direction, from the bloodstream and into the alveoli, where it’s then breathed out into the air. The action of breathing involves muscles contracting and relaxing, depending on whether we want to breathe in or out. Movement of air in and out of the lungs is called ventilation. Lungs
The lungs are very well adapted for gaseous exchange. Instead of being two large sacs, inside each lung are a multitude of little sacs called alveoli. They increase the surface area of the lungs. This means that diffusion can happen at a much faster rate.
THE SMALL INTESTINE
The small intestine absorbs food molecules which are then passes onto the bloodstream and taken to where...
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