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2.2 ­ Gas Exchange (Animals)
Gas Exchange ­ The process of transporting oxygen to cells and transporting carbon dioxide out of

Overcoming problems with size

Thin ­ so that the diffusion paths are short
Permeable ­ To the respirator gases (Oxygen and Carbon Dioxide)
Moist ­ To allow the…

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Important for all exchange organs/surfaces

1. Have a large internal surface area to volume ratio ­ Surface areas are dramatically increased
by dividing them up into small components e.g. Gill plates for fish, Alveoli in the lungs of
humans. The process of air and water intake is called inspiration. The…

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Afferent branchial arteries carries deoxygentated blood from the ventral aorta to the gill capillaries
where gaseous exchange occurs. Oxygenated blood leaves via the efferent branchial vessels.

Water flows over the gills in the same direction of the blood. This is known as parallel flow and is a
very inefficient way…

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The organ of gas exchange is the lungs, which is located in the air tight thorax. The thorax is bound by
the protective ribs and the sheet of muscle known as the diaphragm which separates it from the

Air is warmed by the blood by flowing past blood capillaries…

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Pressure in Thorax Decreases Increases
Atmospheric pressure Greater and so the air moves in Less therefore air moves out

Measurement of Lung capacity

Spirometer: Measures and records the lung volumes and oxygen consumption. A spirometer trace is
called a kymograph.

Tidal volume: The volume of air breathed in and out…


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