When the semilunar valves are open, which of the following are occurring?
(1) Coronary arteries fill
(2) AV valves are closed
(3) Ventricles are in systole
(4) Ventricles are in diastole
(5) Blood enters the aorta
(6) Blood enters pulmonary arteries
(7) Atria contract
a. 2, 3, 5, 6
b. 1, 2, 3, 7
c. 1, 3, 5, 6
d. 2, 4, 5, 7

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Understand the role of semilunar valves: These valves (aortic and pulmonary) open to allow blood to flow from the ventricles into the arteries (aorta and pulmonary artery) during ventricular systole.

Identify what happens when semilunar valves are open: Since blood is being ejected from the ventricles, the ventricles must be contracting, which means they are in systole.

Recall the state of AV valves during ventricular systole: The atrioventricular (AV) valves (mitral and tricuspid) are closed during ventricular systole to prevent backflow of blood into the atria.

Determine which vessels receive blood when semilunar valves are open: Blood flows into the aorta and pulmonary arteries, so blood enters these vessels at this time.

Consider coronary artery filling and atrial contraction: Coronary arteries fill primarily during ventricular diastole when the semilunar valves are closed, and atrial contraction occurs before ventricular systole, so these are not occurring when semilunar valves are open.

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Semilunar Valves and Their Function

Semilunar valves, located at the bases of the aorta and pulmonary artery, open during ventricular systole to allow blood to flow from the ventricles into these arteries. Their opening prevents backflow of blood into the ventricles during diastole, ensuring unidirectional blood flow out of the heart.

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Systole, Diastole, Pressure, & Valves

Ventricular Systole and AV Valve Closure

Ventricular systole is the phase when ventricles contract to pump blood out of the heart. During this phase, the atrioventricular (AV) valves close to prevent blood from flowing back into the atria, maintaining efficient forward circulation.

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Systole, Diastole, Pressure, & Valves

Coronary Artery Filling and Cardiac Cycle Timing

Coronary arteries primarily fill during ventricular diastole when the semilunar valves are closed, allowing blood to flow into these vessels. When semilunar valves are open during systole, coronary filling is minimal, as blood is ejected into the aorta and pulmonary arteries.

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