Question

What is diapedesis?

Answer 1

Hint: Leukocytes (white blood cells) possess nuclei and other cell organelles and can move in an amoeboid fashion. Due to this ability, Leukocytes can squeeze through pores in the capillary walls and move to a site of infection.

Complete answer:
The movements of leukocytes through capillary walls is referred to as diapedesis. The blood vessels are lined with the endothelium, a layer of cells that tends to protect blood cell migration outside of the cells. However, injury or trauma can cause white blood cells to migrate across the endothelium. This process is called diapedesis. As a result of this condition, white cells become part of the interstitial fluid, which surrounds the blood vessels and the tissue cells of the body. The white cells may exhibit diapedesis to fight infection in the tissues surrounding blood vessels. The blood vessels themselves provide a built-in pathway for diapedesis to occur when needed. When the white cells slowly down, they can slip through tiny spaces in the endothelium, called inter-endothelial spaces, which widen in response to the presence of chemicals the body produces in larger numbers during an infection or traumatic injury. The slowdown of the blood cells is also caused by a release of chemicals, which makes the white cells respond to address the infection.

Additional information:
• Part of the swelling due to injury or infection is caused by diapedesis. The white cells are intensely active because as well as destroying bacteria, they also work to form a barrier around an infection that can help prevent the rest of the body from becoming infected. In small localized infections, this effect can be quite beneficial. In larger infections, the migrating infection may overpower the migrating white cells.
• A rare autoimmune disorder called leukocyte adhesion deficiency can imperil the process. With this condition, the body fails to exhibit a chemical response to slow down the white blood cells, thus diapedesis cannot occur.

Note: Observations on the behaviour of circulating leukocytes are difficult. However, techniques such as time-lapse and intravascular microscopy on rabbit ear, mesenteric tissue of mouse or rat, hamster cheek pouch or batwing enabled us to monitor intravascular events and diapedesis.