What is the primary function of the atrioventricular (AV) valves in the heart?
To facilitate blood flow from ventricles to the lungs
To prevent blood from flowing into the coronary arteries
To regulate blood flow between the two ventricles
To prevent backflow of blood into the atria
The Correct Answer is D
A. To facilitate blood flow from ventricles to the lungs:
Blood flow to the lungs occurs via the pulmonic valve and pulmonary artery, not the AV valves.
B. To prevent blood from flowing into the coronary arteries:
Coronary arteries receive blood from the aortic sinuses, independent of AV valves. AV valves do not regulate coronary perfusion.
C. To regulate blood flow between the two ventricles:
Blood does not flow directly between ventricles. AV valves regulate flow from atria to ventricles, not between ventricles.
D. To prevent backflow of blood into the atria:
The mitral and tricuspid valves prevent backflow of blood into the atria during ventricular contraction (systole), ensuring unidirectional blood flow and efficient cardiac output.
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Related Questions
Correct Answer is C
Explanation
A. Epicardium:
The epicardium is the outer layer of the heart that provides protection and contains blood vessels but is not responsible for contraction.
B. Pericardium:
The pericardium is a fibrous sac surrounding the heart that provides protection and reduces friction; it does not contain muscle tissue.
C. Myocardium:
The myocardium is the thick middle layer of cardiac muscle responsible for generating the force of contraction necessary for pumping blood throughout the body. It is metabolically active and highly dependent on coronary artery perfusion.
D. Endocardium:
The endocardium lines the interior of the heart chambers and valves; it provides a smooth surface for blood flow but does not contract.
Correct Answer is B
Explanation
A. S3:
S3 occurs during rapid ventricular filling in early diastole and may indicate volume overload or heart failure, not AV valve closure.
B. S1:
S1 is produced by the closure of the mitral and tricuspid valves at the beginning of ventricular systole. It marks the start of ventricular contraction and is best heard at the apex (mitral) and lower left sternal border (tricuspid).
C. S2:
S2 occurs during closure of the semilunar valves (aortic and pulmonic) at the end of systole, not AV valves.
D. S4:
S4 occurs during atrial contraction in late diastole and is associated with a stiff ventricle; it is not related to AV valve closure.
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