Question

which of the following is caused by ventricular contraction?
multiple choice
blood flows into the ventricles.
blood flows out of the atria
the atrioventricular valves close, and then the semilunar valves open
the semilunar valves close, and then the atrioventricular valves open
pressure becomes greater in the aorta and pulmonary trunk as compared to inside the ventricles

Explanation:

When the ventricles contract, the pressure inside the ventricles rises. This causes the atrioventricular valves (which separate the atria and ventricles) to close to prevent back - flow of blood into the atria. As the ventricular pressure continues to increase and exceeds the pressure in the aorta (for the left ventricle) and pulmonary trunk (for the right ventricle), the semilunar valves open, allowing blood to be ejected from the ventricles.

Blood flows into the ventricles during atrial contraction (not ventricular contraction). Blood flows out of the atria mainly during atrial contraction as well. When the semilunar valves close, it is at the end of ventricular ejection, and then the atrioventricular valves open during ventricular relaxation (diastole). And during ventricular contraction, the pressure in the ventricles is greater than in the aorta and pulmonary trunk (initially), which is why the semilunar valves open.

Answer:

The atrioventricular valves close, and then the semilunar valves open.