## **Core Concept**
The spleen is an organ involved in filtering the blood, storing red blood cells, and serving as a reservoir for immune cells. It plays a critical role in the circulatory system by regulating blood volume and composition.

## **Why the Correct Answer is Right**
The spleen acts as a blood reservoir and contains a significant portion of the body's blood volume. Approximately 300-500 mL of blood is stored in the spleen at any given time, which translates to about 10% of the total blood volume in a healthy adult. This stored blood can be mobilized into the circulation as needed, such as during times of increased oxygen demand or blood loss.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 1-2% is significantly lower than the actual volume stored in the spleen. This option underestimates the spleen's capacity as a blood reservoir.
- **Option B:** 20-30% overestimates the spleen's blood storage capacity. While the spleen does store a considerable amount of blood, it does not hold as much as 20-30% of the total blood volume.
- **Option D:** 50-60% is far too high and not physiologically accurate for the spleen's blood storage capacity.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the spleen's ability to store and release blood helps in maintaining blood pressure and ensuring adequate circulation during periods of need. This function is vital in conditions like hemorrhage, where the spleen can help compensate for blood loss by releasing stored red blood cells into the circulation.

## **Correct Answer:** C. 10%.