Question:medium
A left-sided superior vena cava drains into:
A left-sided superior vena cava drains into:
Show Hint
The left horn of the sinus venosus becomes the coronary sinus; the persistent left vein drains there.
Updated On: Jun 24, 2026
- Right atrium
- Left atrium
- Coronary sinus
- Pericardial space
Show Solution
The Correct Option is C
Solution and Explanation
To answer this, trace the embryology of the great veins. Early in development paired anterior cardinal veins drain the head end of the embryo. On the right side the system goes on to form the normal right superior vena cava. On the left side the anterior cardinal vein is meant to disappear after the left brachiocephalic vein carries its blood across to the right.
When that left vessel fails to regress, it persists as a left superior vena cava running down the left side of the mediastinum. The question is where this extra vein delivers its blood. The left horn of the sinus venosus has already become the coronary sinus, and the persistent left superior vena cava drains straight into that coronary sinus.
Because the coronary sinus opens into the right atrium, the blood does finally reach the right atrium, but only after passing through an enlarged coronary sinus. So the immediate and correct termination named in the options is the coronary sinus, not the right atrium directly. Drainage into the left atrium is a rare cyanotic variant and into the pericardial space does not occur, so those options are wrong.
$\Rightarrow$ a persistent left superior vena cava typically drains into the coronary sinus.
\[\boxed{\text{Coronary sinus}}\]
When that left vessel fails to regress, it persists as a left superior vena cava running down the left side of the mediastinum. The question is where this extra vein delivers its blood. The left horn of the sinus venosus has already become the coronary sinus, and the persistent left superior vena cava drains straight into that coronary sinus.
Because the coronary sinus opens into the right atrium, the blood does finally reach the right atrium, but only after passing through an enlarged coronary sinus. So the immediate and correct termination named in the options is the coronary sinus, not the right atrium directly. Drainage into the left atrium is a rare cyanotic variant and into the pericardial space does not occur, so those options are wrong.
$\Rightarrow$ a persistent left superior vena cava typically drains into the coronary sinus.
\[\boxed{\text{Coronary sinus}}\]
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