Question

What is diapedesis?
a. A kind of amoeboid movement.
b. The process of filtration of urea in the kidney.
c. A type of locomotion found in Hydra.
d. Migration of WBCs into the tissue spaces from blood capillaries.

Answer 1

Diapedesis is also known as leukocyte extravasation, and commonly called as leukocyte adhesion cascade, in this process leukocytes move towards the tissue damage. Where it is a form of an innate immune response in the body and sometimes it involves nonspecific leukocyte.

Complete answer:
- In Diapedesis the WBC moves out of the circulatory system, in order to reach the damaged or infected tissue.
- Diapedesis mostly occurs in Post capillary venules.
- Whenever there is damage in the tissue or pathogen attack, the WBC reach that tissue by diapedesis, There are several steps which include following

Chemoattraction: Whenever there is recognition or activation of pathogens, resident macrophages release cytokines and interleukins, and at the same time, endothelial cells express some cellular adhesion molecules selectins, because of all chemicals leukocytes circulating in local blood vessels travel to the damaged site.

Rolling and adhesion: Because of selections, released by the endothelial cells the circulating leukocytes adhere to the line of endothelium and start rolling.

Tight adhesion: The cytokines released by the macrophages, attract the leukocytes and also cause the integrins which cause the WBC immobilization and results in tight adhesion.

Transmigration: The leukocyte from the adhered molecules forms the pseudopodia with which WBC moves from the adhered wall to the damage site and this movement is called diapedesis.

Hence, the correct answer is option (D).

Note: In some people there is a defect in integrins beta chains, in those people leukocytes are incapable to do diapedesis, such people suffer from leukocyte adhesion deficiency, and in these people there is always recurrent infections, and impaired wound healing is seen.