The movement of Neutrophils into tissues is called as:

Question

Accepted Answer

The correct option is 3: Extravasation

Extravasation is the highly specific and essential mechanism by which a neutrophil, or any other leukocyte, actively navigates from the circulating bloodstream to the site of inflammation or infection within the surrounding tissues. This process is a cornerstone of the acute immune response and is also known as diapedesis or the leukocyte adhesion cascade. The movement is not random; it is a meticulously coordinated, multi-step sequence involving sequential interactions with the endothelial cells lining the blood vessel wall. This cascade includes initial tethering and rolling, followed by firm adhesion mediated by specific molecular receptors (such as integrins), and culminates in the cell squeezing itself between the endothelial cell junctions and migrating through the basement membrane into the interstitial tissue, directed by chemical signals called chemokines.

The incorrect option is 1: Diffusion

Diffusion is a passive physical process that describes the net movement of molecules, not entire cells, from an area of higher concentration to an area of lower concentration, down a concentration gradient. This process is non-specific, does not require cellular energy (ATP), and is characteristic of the movement of small solutes or gases like oxygen. Neutrophils are large, complex cells whose directed migration is an active, energy-consuming process guided by chemotaxis (chemical gradients). Therefore, the process of a neutrophil selectively exiting the vascular system to enter a tissue cannot be accurately described as simple diffusion.

The incorrect option is 2: Internalization

Internalization is a general term in cell biology used to describe the uptake of extracellular material *into* the cell's cytoplasm, typically through processes like endocytosis or pinocytosis. It refers to how the cell acquires substances from its immediate external environment across its own membrane. This term describes the consumption or uptake of a substance (e.g., a receptor, a nutrient, or a toxin) by the cell, and it is entirely distinct from the process of the entire cell moving out of a blood vessel. Although neutrophils will internalize pathogens later on, the term does not describe the complex, trans-endothelial migration into tissue.

The incorrect option is 4: Phagocytosis

Phagocytosis is a primary function of neutrophils after they have successfully arrived at the site of infection, not the process of their movement to that site. This term literally means 'cell eating' and describes the active process where a cell engulfs solid particles, such as invading bacteria, foreign debris, or dying host cells, into an internal vesicle called a phagosome. While phagocytosis is the ultimate goal and principal weapon of the neutrophil in the tissues, it is a destructive action of the immune cell. It does not refer to the migratory process of escaping the blood vessel, which is correctly termed extravasation.