Which organ of human body acts as both blood bank and graveyard of RBCS?

Explanation

**Step-by-Step Solution:**

1. **Identify the Organ**: The question asks for an organ in the human body that functions as both a blood bank and a graveyard for red blood cells (RBCs).

2. **Understanding the Functions**:
- **Blood Bank Function**: The spleen stores a reserve of RBCs that can be released into the bloodstream during emergencies, such as significant blood loss due to injury or hemorrhage. This function is crucial for maintaining blood volume and ensuring adequate oxygen delivery to tissues during critical situations.
- **Graveyard Function**: The spleen is also responsible for the destruction of old or damaged RBCs. The average lifespan of an RBC is about 120 days. When they age, they are recognized and engulfed by macrophages (a type of immune cell) in the spleen, where they are broken down and recycled.

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