d r e a m y
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Hi, the question says "Explain how it is possible for blood to return to the heart when the vein pressures are so low"

The mark scheme reads:
"Massaging effect / contraction of muscles / (prevention of backflow) by valves /suction effect of the relaxing heart (not less resistance due to wider lumen)".

I don't understand the answers here, could someone explain as online ones are in too much detail for a 1 marker.
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Mapleservers
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Seems a big question for a 1 marker - I’m assuming you only have to give a short example? Probably 10 words maximum
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Mapleservers
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The valves direct the blood heartwards and prevent it from falling back again
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d r e a m y
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(Original post by Mapleservers)
Seems a big question for a 1 marker - I’m assuming you only have to give a short example? Probably 10 words maximum
The answer is "Massaging effect / contraction of muscles / (prevention of backflow) by valves /suction effect of the relaxing heart (not less resistance due to wider lumen)" but I dont get it
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d r e a m y
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(Original post by Mapleservers)
The valves direct the blood heartwards and prevent it from falling back again
okay tyy
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raspbewwies
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(Original post by d r e a m y)
Hi, the question says "Explain how it is possible for blood to return to the heart when the vein pressures are so low"

The mark scheme reads:
"Massaging effect / contraction of muscles / (prevention of backflow) by valves /suction effect of the relaxing heart (not less resistance due to wider lumen)".

I don't understand the answers here, could someone explain as online ones are in too much detail for a 1 marker.
Filling of the heart during diastole (when it relaxes) is due to the pressure in the right atrium falling below venous pressure, encouraging venous flow. That's the key reason - contraction of muscles and valves help avoid venous stasis (blood pooling).

Source: med school

Hope that helps!
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d r e a m y
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(Original post by raspbewwies)
Filling of the heart during diastole (when it relaxes) is due to the pressure in the right atrium falling below venous pressure, encouraging venous flow. That's the key reason - contraction of muscles and valves help avoid venous stasis (blood pooling).

Source: med school

Hope that helps!
OHH!! Thank you!!!!
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Jpw1097
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(Original post by d r e a m y)
Hi, the question says "Explain how it is possible for blood to return to the heart when the vein pressures are so low"

The mark scheme reads:
"Massaging effect / contraction of muscles / (prevention of backflow) by valves /suction effect of the relaxing heart (not less resistance due to wider lumen)".

I don't understand the answers here, could someone explain as online ones are in too much detail for a 1 marker.
Venous blood from above the level of the heart is returned via gravity. In the legs, contraction of muscles in the legs squeezes the veins and pushes blood back to the heart. The reason why venous blood only moves towards the heart when muscles contract is because of the valves, which prevent the back flow of blood. Also, during inspiration, the thorax expands and the intrathoracic pressure (including the heart) decreases, which increases venous return.
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