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­ 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 gases to dissolve into the layer of moisture before diffusing into the
Have a sufficiently large surface area to satisfy the needs of the organism
Must be able to maintain a concentration gradient
Gas Exchange…read more

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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 expulsion of water and
air is called expiration.
2. Thin ­ Diffusion paths must be short so that oxygen diffuses into the bloodstream quickly and
carbon is removed quickly.
3.…read more

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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 of obtaining oxygen from water. A diffusion gradient is not maintained an
equilibrium is soon reached.
Bony Fish
Bony fish have four pairs of branchial arches supporting the gill lamelle in the pharynx.…read more

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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
abdomen.…read more

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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 in one breathing cycle.
Tidal volume at rest = 500 cm3
350cm3 reaches the alveoli where is mixes with stationary air which is not moved in tidal breathing at
rest, and where gaseous exchange occurs.…read more


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