What is the function of the pericardial sac surrounding the heart?
To regulate heart rate
To contract and assist with blood pumping
To provide a lubricated environment for the heart
To store blood during diastole
The Correct Answer is C
A. To regulate heart rate:
Heart rate is controlled by the SA node and autonomic nervous system, not the pericardial sac.
B. To contract and assist with blood pumping:
The pericardium is non-contractile; it does not generate force to pump blood.
C. To provide a lubricated environment for the heart:
The pericardial sac contains pericardial fluid that reduces friction between the heart and surrounding structures during contraction and relaxation, protecting the heart from mechanical stress.
D. To store blood during diastole:
The pericardium does not store blood; ventricular chambers store blood transiently during diastole.
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Related Questions
Correct Answer is C
Explanation
A. Coronary arteries are filled with blood during atrial contraction:
Coronary arteries are primarily perfused during diastole, not atrial contraction. During systole, contraction of the ventricles compresses the coronary vessels, reducing blood flow.
B. Coronary circulation occurs only during systole:
Coronary blood flow mostly occurs during diastole, because the myocardial contraction during systole compresses the coronary vessels, especially in the left ventricle.
C. Coronary veins return deoxygenated blood to the right atrium:
Coronary veins collect deoxygenated blood from the myocardium and empty it into the right atrium via the coronary sinus, completing the coronary circulation.
D. Coronary arteries supply deoxygenated blood to the heart muscle:
Coronary arteries supply oxygenated blood to the heart muscle, not deoxygenated blood.
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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