When atria contract, blood does not enter into pulmonary vein or superior vena cava because
O These openings are guarded by semilunar valves
O Pulmonary vein has Thebesian valve and superior vena cava has oblique opening
O Both pulmonary vein and superior vena cava has oblique openings which closes
O Eustachian valve closes superior vena cava and semilunar valve closes pulmonary vein
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4 th one option is correct i think .......
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