## **Core Concept**
The process by which white blood cells (WBCs) can move through the capillary walls is crucial for their function in reaching sites of infection or inflammation. This involves specific interactions between WBCs and the endothelial lining of blood vessels.

## **Why the Correct Answer is Right**
The correct answer, **diapedesis**, refers to the process by which WBCs can squeeze through the pores or gaps between endothelial cells lining the capillaries and postcapillary venules. This process is essential for the migration of leukocytes from the bloodstream into tissues where they are needed to fight infection or inflammation. It involves changes in the shape of the leukocytes and the opening of gaps between endothelial cells, facilitated by adhesion molecules.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and does not provide a viable choice for the process described.
- **Option B:** This option is also blank and does not offer a relevant process related to WBC movement through capillary walls.
- **Option C:** This option is blank as well, failing to provide a recognized term for the described phenomenon.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that diapedesis is a critical step in the inflammatory response, allowing WBCs to reach the site of infection or injury. This process is tightly regulated by adhesion molecules and chemokines, which guide the WBCs to their destination.

## **Correct Answer:** D. diapedesis