AQA AS Biology 13.6 Blood Vessels and their functions
1. What is the function of an artery?: to transport blood rapidly under high
pres- sure from the heart to the tissues
2. What are arterioles?: smaller arteries that control blood flow from
arteries to capillaries
3. What are capilliaries?: tiny vessels that link arterioles to veins
4. What do veins carry?: blood from capillaries back to the heart
5. What basic layered structure do arteries, arterioles and veins have?:
tough outer layer, muscle layer, elastic layer, thin inner layer
(endothelium), lumen
6. What does the tough outer layer in blood vessels resist?: pressure
changes from both within and outside
7. What does the muscle layer in blood vessels do?: contract and so
control the flow of blood
8. What does the elastic layer in blood vessels help maintain?: blood
pressure by stretching and springing back
9. Why is the endothelium smooth and thin?: to prevent friction and allow
diffu- sion
10.What is the lumen?: the central cavity of the blood vessel through
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, which blood flows
11.What differs in structure between each type of blood vessel? What are
the differences related to?: the relative proportion of each layer
the differences in the vessels functions
12.Why is the muscle layer in arteries thick compared to veins?: so that
smaller arteries can be constricted and dilated in order to control the
volume of blood passing through them
13.Why is the elastic layer in arteries relatively thick compared to arteries?:
- important that the blood pressure in kept high if blood is to reach the
exremities of the body
14.Why is the overall thickness of the artery wall large?: to resist the
vessel burting under pressure
15.Why are there no valves in arteries? (except in arteries leaving heart):
blood is under constant high pressure and so does not tend to flow
backwards
16.What does the contraction of the muscle layer in arterioles allow? This
restricts the flow of blood, what does this control?: the constriction of the
lumen its movement into the capillaries that supply the tissues with
blood
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1. What is the function of an artery?: to transport blood rapidly under high
pres- sure from the heart to the tissues
2. What are arterioles?: smaller arteries that control blood flow from
arteries to capillaries
3. What are capilliaries?: tiny vessels that link arterioles to veins
4. What do veins carry?: blood from capillaries back to the heart
5. What basic layered structure do arteries, arterioles and veins have?:
tough outer layer, muscle layer, elastic layer, thin inner layer
(endothelium), lumen
6. What does the tough outer layer in blood vessels resist?: pressure
changes from both within and outside
7. What does the muscle layer in blood vessels do?: contract and so
control the flow of blood
8. What does the elastic layer in blood vessels help maintain?: blood
pressure by stretching and springing back
9. Why is the endothelium smooth and thin?: to prevent friction and allow
diffu- sion
10.What is the lumen?: the central cavity of the blood vessel through
1/
, which blood flows
11.What differs in structure between each type of blood vessel? What are
the differences related to?: the relative proportion of each layer
the differences in the vessels functions
12.Why is the muscle layer in arteries thick compared to veins?: so that
smaller arteries can be constricted and dilated in order to control the
volume of blood passing through them
13.Why is the elastic layer in arteries relatively thick compared to arteries?:
- important that the blood pressure in kept high if blood is to reach the
exremities of the body
14.Why is the overall thickness of the artery wall large?: to resist the
vessel burting under pressure
15.Why are there no valves in arteries? (except in arteries leaving heart):
blood is under constant high pressure and so does not tend to flow
backwards
16.What does the contraction of the muscle layer in arterioles allow? This
restricts the flow of blood, what does this control?: the constriction of the
lumen its movement into the capillaries that supply the tissues with
blood
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