Circulatory Systems T1
- Created by: tiasjw
- Created on: 20-05-16 11:36
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- Circulatory Systems
- Open
- Small organisms e.g. insects
- Distances are short so substances can travel by diffusion
- A simple heart pumps blood into cavities surrounding the animal's organs
- Substances diffuse between the blood and cells
- When the heart relaxes blood is drawn back into the heart through small valved openings
- Closed
- Multicellular organisms that are too large for diffusion; animals are usually larger in size and more active
- Rely on a mass transport system to move substances by mass flow
- The heart pumps blood and the blood and the particles in it move through blood vessels due to difference in pressure
- Blood vessels generate higher blood pressures as the blood is forced along narrow channels instead of flowing into large cavities
- The blood travels faster so the blood system is more efficient
- Blood leaves the heart, flows along arteries and then arterioles, blood comes into close contact with capillaries where substances are exchanged, blood returns to heart by venules and veins
- Single
- For animals with closed systems
- For example fish; heart pumps blood to gills, gaseous exchange takes place in gills, blood leaving gills then flows round rest of the body before returning to heart
- Blood flows through the heart once for each complete circuit of the body
- Double
- For animals with closed systems
- For example birds and mammals: right ventricle pumps oxygenated blood to lungs where it receives oxygen, the oxygenated blood then returns to heart to be pumped a second time by the left ventricle to the rest of the body
- Blood flows through the heart twice foe each complete circuit of the body, giving blood returning from the lungs an 'extra boost'
- Birds & mammals have a high metabolic rate, as substances can be delivered to cells more rapidly
- Open
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