Stroke volume (SV) refers to the amount of blood pumped by which ventricle?
Both ventricles
Left ventricle
Right ventricle
Both atria
The Correct Answer is A
A. Both ventricles: Stroke volume (SV) is the volume of blood ejected by a ventricle during a single contraction, measured from end-diastolic volume minus end-systolic volume. The left ventricle pumps blood into systemic circulation, while the right ventricle pumps blood into the pulmonary circulation, making SV a measure relevant to both ventricles.
B. Left ventricle: The left ventricle pumps oxygenated blood into the aorta for systemic circulation. While left ventricular SV is often emphasized clinically due to systemic perfusion, stroke volume is conceptually defined for both ventricles, not exclusively the left.
C. Right ventricle: The right ventricle ejects deoxygenated blood into the pulmonary trunk for gas exchange in the lungs. Like the left ventricle, it contributes to the stroke volume, so SV is not limited solely to the right ventricle.
D. Both atria: The atria function as filling chambers that contribute to ventricular preload by delivering blood through the atrioventricular valves. While atrial contraction assists ventricular filling, stroke volume specifically refers to blood ejected from the ventricles, not the atria.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. The atria and ventricles are in diastole, and the atrioventricular valves are open: At the beginning of the cardiac cycle, both the atria and ventricles are relaxed (diastole). The atrioventricular (tricuspid and mitral) valves are open due to higher atrial pressure compared to ventricular pressure, allowing passive ventricular filling. This phase establishes the end-diastolic volume and prepares the ventricles for subsequent contraction.
B. The atria are in systole, the ventricles are in diastole, and the semilunar valves are open: During atrial systole, the atria contract to complete ventricular filling, but the semilunar valves remain closed because ventricular pressure has not yet exceeded the pressure in the aorta or pulmonary trunk.
C. The atria and ventricles are in systole, and all valves are open: Both chambers are never in systole simultaneously. If both contracted at once, it would impair filling and ejection, and physiologically, the valves are not all open at the same time.
D. The atria and ventricles are in diastole, and the semilunar valves are open: Semilunar valves (aortic and pulmonary) open only when ventricular pressure exceeds arterial pressure during ventricular systole. At the start of the cycle, ventricles are relaxed, so the semilunar valves remain closed.
Correct Answer is A
Explanation
Correct answer: True
The endocardium is a thin, smooth membrane that lines the internal chambers of the heart, including the atria, ventricles, and heart valves. It is composed of endothelial cells and connective tissue, providing a non-thrombogenic surface that minimizes friction as blood flows through the heart. The endocardium plays a critical role in maintaining efficient circulation, regulating myocardial function, and forming the inner lining of the heart valves to ensure unidirectional blood flow. Its anatomical location within the heart chambers allows it to serve as a protective barrier between the blood and the myocardium, supporting both structural integrity and optimal cardiac performance.
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