What is the role of the coronary sinus in coronary circulation?
It supplies oxygenated blood to the heart
It supplies the interventricular septum with oxygenated blood
It drains deoxygenated blood from the myocardium
It regulates coronary blood flow
The Correct Answer is C
A. It supplies oxygenated blood to the heart:
The coronary sinus does not supply blood; this is the role of coronary arteries.
B. It supplies the interventricular septum with oxygenated blood:
The interventricular septum is supplied mainly by the left anterior descending artery, not the coronary sinus.
C. It drains deoxygenated blood from the myocardium:
The coronary sinus collects deoxygenated blood from the cardiac veins and empties it into the right atrium, completing the venous return from the myocardium. This is essential for maintaining myocardial oxygen balance.
D. It regulates coronary blood flow:
Coronary blood flow is regulated by autonomic control and local metabolic demand, not by the coronary sinus.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Supplies the lateral wall of the left ventricle:
The circumflex artery branches from the left coronary artery and supplies the lateral and posterior walls of the left ventricle as well as part of the left atrium. This supply is crucial for maintaining effective left ventricular contraction and overall cardiac output.
B. Supplies the right ventricle:
The right ventricle is primarily supplied by the right coronary artery, not the circumflex artery. Misidentifying this can affect understanding of infarct locations.
C. Supplies the interventricular septum:
The interventricular septum is mainly supplied by the LAD artery, which is critical for coordinating left ventricular contraction.
D. Supplies the right atrium:
The right atrium is primarily supplied by the RCA, not the circumflex artery. Understanding arterial supply is important for predicting conduction system involvement in MI.
Correct Answer is B
Explanation
A. Heart failure:
Heart failure involves impaired cardiac output due to structural or functional heart abnormalities. Although pericardial effusion can eventually reduce cardiac output, the direct complication of excessive fluid is not standard heart failure but cardiac tamponade, a more acute and dangerous condition.
B. Cardiac tamponade:
Excess fluid in the pericardial sac creates pressure that restricts ventricular filling, reducing stroke volume and cardiac output. This can rapidly lead to hypotension, muffled heart sounds, and jugular venous distention-a classic triad known as Beck’s triad. Cardiac tamponade is a life-threatening emergency requiring prompt intervention.
C. Pulmonary embolism:
Pulmonary embolism occurs when a clot lodges in the pulmonary arteries. It is unrelated to pericardial fluid accumulation and arises from thromboembolic events, not fluid pressure on the heart.
D. Myocardial infarction:
Myocardial infarction occurs due to coronary artery blockage, leading to ischemia. While tamponade can reduce cardiac output, it does not directly cause a myocardial infarction.
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