During ventricular systole
Correct answer: A. the ventricles contract and the semilunar valves open
- A. the ventricles contract and the semilunar valves open
- B. the ventricles relax and fill with blood
- C. the semilunar valves close
- D. the atrioventricular valves open wide
Explanation
Systole means contraction: rising pressure in the ventricles closes the inlet atrioventricular valves and forces open the semilunar valves, ejecting blood into the arteries. Relaxation, diastole, is the opposite phase.
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The human heart is a four chambered muscular pump that maintains double circulation through the pulmonary and systemic circuits. Questions cover atria, ventricles, valves, major blood vessels, the cardiac cycle, pressure changes, the conduction system and ECG, while distinguishing arteries and veins from the chambers that receive or eject blood.
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