**Question:** Process of migration of leukocytes through the endothelium is through

A. Transmigration
B. Extravasation
C. Transendothelial migration
D. Extravasation and Transendothelial migration

**Core Concept:**

Leukocyte migration, also known as leukocyte transmigration, is a crucial process that occurs during immune responses and inflammation. Leukocytes, such as neutrophils, monocytes, and lymphocytes, need to move from blood vessels into tissues to participate in the immune response against pathogens or perform their physiological functions. This process involves several steps:

**Why the Correct Answer is Right:**

The correct answer is **C. Transendothelial migration**. This is the term referring to the movement of leukocytes across the endothelium, which is the inner layer of cells lining the blood vessels. This process occurs during inflammation or infection, allowing leukocytes to enter the surrounding tissue and interact with infected or damaged cells.

**Why Each Wrong Option is Incorrect:**

A. **Transmigration** (Option A) is a term related to the movement of cells across the endothelial layer, but it is not specific to leukocytes. It describes the overall migration of cells across the endothelium, which includes not only leukocytes but also other cell types.

B. **Extravasation** (Option B) is a broad term that describes the process of a cell leaving the bloodstream and entering the surrounding tissue. While it involves leukocytes, it does not specifically describe the process of leukocyte migration across the endothelium.

D. **Extravasation and Transendothelial migration** (Option D) combines the two incorrect options A and B, further emphasizing the need to separate the specific term for leukocyte migration.

**Clinical Pearl:**

Understanding leukocyte migration is crucial for medical professionals as it allows them to comprehend the pathophysiology of inflammatory and immune responses. A good understanding of this process helps in diagnosing, treating, and managing patients with inflammatory or autoimmune conditions.

**Correct Answer:** C. Transendothelial migration