In order for blood to enter the heart,

Question

Quizplus · Accepted Answer

For blood to enter the heart, the atria must not only be at rest (in diastole) but also have a lower pressure than the veins. This pressure gradient allows the blood to flow from the veins into the atria through the open AV valves. Choice A is incorrect as it only refers to the relaxation of the atria, but does not address the pressure gradient. Choice B is also incorrect as it refers to the pressure in the atria being lower than in the veins, which is the opposite of what is required for blood to enter the heart. Choice C is partially correct, as the AV valves must be open, but this alone does not allow for blood to enter the heart if the pressure gradient is not present. Therefore, the best choice is D.

In Order for Blood to Enter the Heart