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 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.

Verified step by step guidance

1. Identify the function of semilunar valves: they prevent backflow of blood from the arteries into the ventricles and are open during ventricular systole.
2. Understand that during ventricular systole, the ventricles contract, pushing blood into the aorta and pulmonary arteries, so options 5 and 6 are likely correct.
3. Recognize that when the semilunar valves are open, the AV valves (atrioventricular valves) are closed to prevent backflow into the atria, so option 2 is likely correct.
4. Note that ventricular systole is the phase when the ventricles contract, so option 3 is likely correct.
5. Review the options and match the correct statements with the choices given, focusing on the combination that includes 2, 3, 5, and 6.

Key Concepts

Semilunar Valves

Semilunar valves are located at the exit of the heart's ventricles, specifically the aortic and pulmonary valves. They open during ventricular contraction (systole) to allow blood to flow into the aorta and pulmonary arteries, and close during diastole to prevent backflow into the ventricles. Understanding their function is crucial for analyzing the cardiac cycle and the events occurring during valve openings.

Ventricular Systole and Diastole

Ventricular systole refers to the phase when the ventricles contract, pumping blood into the aorta and pulmonary arteries, while diastole is the phase when the ventricles relax and fill with blood. During systole, the semilunar valves are open, and the AV valves are closed to prevent backflow. Recognizing these phases is essential for determining which events occur when the semilunar valves are open.

Coronary Arteries and Blood Flow

Coronary arteries supply blood to the heart muscle itself and primarily fill during diastole when the heart is relaxed. When the semilunar valves are open, blood is being ejected from the ventricles, which means the coronary arteries are not filling at that moment. Understanding the timing of blood flow in relation to the cardiac cycle is vital for answering questions about heart function.