Circulatory system - blood vessels
- Created by: cassiarh01
- Created on: 18-04-18 17:43
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- Circulatory system - blood vessels
- Arteries carry blood under pressure
- Carry blood away from the heart
- Heart pumps blood out at high pressure
- Artery walls are strong and elastic
- Have thick layers of muscle to make them strong
- Have elastic fibres to allow them to stretch and spring back
- Thick walls compared to the size of the hole down the middle - 'lumen'
- Capillaries are really small
- Arteries branch into capillaries
- Carry blood really close to every cell in the body to exchange substances with them
- Have gaps in their walls so substances can diffuse in and out
- Supply food and oxygen and take away CO2
- Walls are usually one cell thick - diffuse very fast because there is only a short distance for molecules to travel
- Very small lumen
- Veins take blood back to the heart
- Join up to form veins
- Blood is at a lower pressure in the veins - walls don't need to be as thick as artery walls
- Veins have a bigger lumen than artieries which helps the blood flow despite a lower pressure
- Also have valves - help to keep the blood flowing in the right direction
- Calculating the rate of blood flow
- Rate of blood flow = volume of blood / number of minutes
- Arteries carry blood under pressure
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