Define end-systolic volume (ESV).

• A. The volume of blood ejected during systole
• B. The volume of blood in the ventricle at the end of diastole
• C. The total blood volume in the ventricle during the cardiac cycle
• D. The volume of blood remaining in the ventricle after contraction

Answer: (D)

End-systolic volume is the amount of blood left in a ventricle after it finishes contracting (after systole). As the ventricle ejects blood into the aorta or pulmonary artery, some blood remains behind, and that remaining volume is the end-systolic volume. This value, together with the end-diastolic volume (the volume at the end of filling), determines stroke volume: SV equals EDV minus ESV. In a typical heart, EDV is about 120 ml and ESV around 50 ml, giving a stroke volume of about 70 ml. ESV is influenced by how forcefully the heart contracts (contractility) and by the afterload, the pressure the heart must work against; stronger contraction lowers ESV, while higher afterload tends to raise it. So end-systolic volume specifically describes what remains after the ventricle has finished ejecting blood, not the amount ejected or the volume at diastole.