The beginning of ventricular systole is when blood flowing back toward the relaxed ventricles causes the semilunar valves to close. The beginning of ventricular systole is when blood flowing back toward the relaxed ventricles causes the semilunar valves to close. A) TrueB) False

The correct answer is "False".

Explanation:

The ventricular systole occurs when pressure rises in the ventricles causing that blood pumps from the right ventricle and into the aorta from the left ventricle. The beginning of this step is given when blood flowing back towards the atria, closing the tricuspid and mitral valves. It is false that the blood flows back towards the relaxed ventricles as it is stated in the question.

false.

Explanation:

These are the valves between the aorta and the left ventricles and between the pulmonary artery and the right ventricle.

Ventricular systole  begins when the atrioventricular valves closes up  due to rise in  the pressure in the ventricles and the opening of  seminular valves  for blood to leave the ventricles into pulmonary and systemic circulation.

This signifies the beginning of ventricular contraction, as the  closure of the atrioventricular Valves between the atria and the  ventricles prevent the mixing up of oxygenated blood and deoxygenated blood in the ventricles . It ensures complete emptying of the  ventricles before returning blood from  the atria  enters again for another cycle.

.

Collectively they (semilunar valves)prevent back flow of blood from the arteries(aorta and pulmonary arteries) back into the ventricles.

individual oxygen atoms are formed during photosynthesis.-c.

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