Which of the following does not drain into coronary sinus: March 2009
**Question:** Which of the following does not drain into coronary sinus: March 2009
**Core Concept:** The coronary sinus is a large vein that collects blood from the right ventricle, right atrium, and the majority of the myocardium. The coronary sinus receives blood from the subepicardial and subendocardial layers of the heart muscle.
**Why the Correct Answer is Right:**
The correct answer is **D**: The pulmonary veins.
The pulmonary veins are veins that carry deoxygenated blood from the lungs to the left atrium. They are excluded from the coronary sinus because they have their own drainage pathway into the left atrium and subsequently into the left ventricle. The pulmonary veins do not contribute to the oxygenated blood supply to the heart muscle, as this is provided by the coronary arteries.
**Why Each Wrong Option is Incorrect:**
A. **Coronary artery**: This option is incorrect as the coronary arteries supply oxygenated blood to the heart muscle and thus do not drain into the coronary sinus.
B. **Right atrium**: While the right atrium is a part of the heart, it is not a structure that drains into the coronary sinus. The right atrium receives oxygenated blood from the superior and inferior vena cava and sends it to the right ventricle.
C. **Right ventricle**: Similar to the right atrium, the right ventricle receives oxygenated blood from the pulmonary veins and sends it to the pulmonary artery, not into the coronary sinus.
**Clinical Pearl:** The understanding of cardiac anatomy and the cardiovascular system is crucial for healthcare professionals, especially doctors and nurses, to accurately diagnose and treat cardiovascular diseases. Adequate knowledge of cardiac anatomy helps in recognizing and managing cases involving the heart, such as myocardial infarctions, arrhythmias, and heart failure.
**Correct Answer:** D. **Pulmonary veins**
**Explanation:** As mentioned earlier, pulmonary veins carry deoxygenated blood from the lungs to the left atrium and do not contribute to the oxygenated blood supply to the heart muscle. Therefore, they do not drain into the coronary sinus.