End diastolic volume (EDV)

End diastolic volume (EDV) is the amount of blood in a ventricle at the end of diastole, right before systole starts. In Anatomy and Physiology I, it shows how much the ventricle has filled and sets up the next stroke volume.

What is end diastolic volume (EDV)?

End diastolic volume (EDV) is the volume of blood in a ventricle after the heart finishes filling and just before it contracts. In Anatomy and Physiology I, you usually meet it in the cardiac cycle, where it marks the end of ventricular diastole and the starting point for ventricular systole.

Think of EDV as the ventricle’s preload, or the amount of stretch on the ventricle wall before contraction. The more blood that returns to the heart during venous return, the higher the EDV tends to be. That extra filling stretches the cardiac muscle fibers, which can affect how forcefully the next contraction happens.

EDV is not the blood that has already been pumped out. It is the blood still sitting in the ventricle at the end of filling, after atrial contraction has topped off the chamber. This matters because the ventricle can only eject part of that volume during systole, not all of it. The leftover blood after contraction becomes the end systolic volume, which is a different cardiac-cycle value.

A simple way to picture it is to follow one left ventricle through a heartbeat. During diastole, blood enters from the left atrium through the atrioventricular valve. Near the end of filling, the ventricle reaches its maximum volume for that beat, which is the EDV. Then systole begins, the ventricle contracts, and some of that blood leaves through the aortic valve into the aorta.

EDV is one of the numbers that helps explain stroke volume. If filling increases and the heart can contract effectively, stroke volume often rises too. That is why EDV shows up in cardiac cycle diagrams, pressure-volume loops, and questions about how blood flow changes with exercise, hydration, or changes in venous return.

Why end diastolic volume (EDV) matters in Anatomy and Physiology I

EDV matters because it connects filling to pumping. When you are tracing the cardiac cycle, EDV tells you how much blood the ventricle has ready to eject before contraction begins. That makes it one of the starting values for figuring out stroke volume, which is the amount of blood actually pumped out in one beat.

This term also helps explain how the heart responds to changing body demands. During exercise, venous return often rises, so EDV can increase. In response, the ventricle stretches more and may contract more strongly, which lets the heart move more blood per beat without needing a huge jump in heart rate.

In A&P, EDV shows up any time you compare phases of the cardiac cycle, label chamber volume in a diagram, or interpret how one change affects another. If you mix up EDV with the amount pumped out, you will get the rest of the cycle wrong too. Once you know what EDV is, the logic of preload, stroke volume, and cardiac output becomes much easier to track.

How end diastolic volume (EDV) connects across the course

Diastole

EDV happens at the end of diastole, when the ventricles have finished filling. If you know where diastole starts and ends, you can place EDV at the exact point just before ventricular contraction begins. It is the last volume measurement before systole starts.

Systole

Systole is the contraction phase that follows EDV. Once the ventricle contracts, pressure rises and blood is ejected out of the heart. EDV gives you the starting volume for that contraction, so it helps you compare what goes in before systole and what comes out during it.

Stroke Volume (SV)

Stroke volume is calculated from the difference between what the ventricle has before contraction and what remains after it contracts. EDV is the before value in that relationship. If EDV changes and the other variables stay the same, stroke volume can change too.

Frank-Starling Law

Frank-Starling Law explains why a higher EDV can lead to a stronger contraction. More filling stretches the ventricular muscle fibers, and that stretch can increase the force of the next beat. This is why EDV is not just a number, but part of the heart’s built-in adjustment system.

Is end diastolic volume (EDV) on the Anatomy and Physiology I exam?

A quiz question might show a cardiac cycle diagram and ask you to identify the point where the ventricle contains the most blood before contraction. That is EDV. You may also be asked to use EDV in a stroke volume problem, compare it to end systolic volume, or explain what happens to filling when venous return increases. In diagram labeling, look for the chamber volume right after filling and right before the ventricle contracts. In short-answer questions, connect EDV to preload, ventricular stretch, and the start of systole instead of treating it like a random memorization term.

End diastolic volume (EDV) vs end systolic volume

End diastolic volume is the maximum amount of blood in a ventricle right before contraction, while end systolic volume is what remains after contraction. EDV is the starting volume for a beat, and end systolic volume is the leftover volume after some blood has been ejected. Mixing them up flips the logic of stroke volume.

Key things to remember about end diastolic volume (EDV)

• End diastolic volume is the amount of blood in a ventricle at the end of filling, just before systole begins.

• EDV is tied to preload, which is the stretch on ventricular muscle before contraction.

• A higher EDV usually means more venous return and can support a larger stroke volume.

• EDV is one of the main reference points in the cardiac cycle because it marks the transition from filling to pumping.

• Do not confuse EDV with end systolic volume, which is the blood left in the ventricle after contraction.

Frequently asked questions about end diastolic volume (EDV)

What is end diastolic volume (EDV) in Anatomy and Physiology I?

End diastolic volume is the amount of blood in a ventricle after it has finished filling and right before it contracts. In A&P, it is used to describe the starting volume for ventricular systole. It is usually discussed with stroke volume, preload, and the cardiac cycle.

Is EDV the same as stroke volume?

No. EDV is the amount of blood in the ventricle before contraction, while stroke volume is the amount actually pumped out during that contraction. Stroke volume depends on EDV, but the two values are not the same. If you mix them up, you lose track of how much blood stayed behind after the beat.

What happens if end diastolic volume increases?

If EDV increases, the ventricle fills with more blood and stretches more before contracting. That often increases the force of contraction through the Frank-Starling mechanism, which can raise stroke volume. In class problems, this usually shows up as a change in venous return or preload.

How do I identify EDV on a cardiac cycle diagram?

Look for the point where ventricular filling is complete and contraction has not started yet. It is the maximum ventricular volume for that heartbeat, just before pressure rises sharply in systole. If a diagram shows volumes across the cycle, EDV is the highest point right before ejection begins.