Final answer:
Diapedesis is the process where leukocytes move from the bloodstream into tissues, primarily occurring at capillary walls. Adhesion, signaling, and morphological changes in leukocytes facilitate this process, enabling an essential part of the immune response.
Step-by-step explanation:
Diapedesis, also known as emigration, is the process by which leukocytes (white blood cells) squeeze through adjacent cells in a blood vessel wall to enter tissues. This process predominantly occurs at capillary walls where leukocytes pass through to reach infected tissues. Adhesion, cellular signaling, and changes in the leukocytes' shape and flexibility facilitate their movement from the bloodstream into surrounding tissues.
The facilitation of diapedesis involves a series of steps. Initially, the leukocytes adhere to the vessel wall through interactions with adhesion molecules. Signaling between cells triggers the leukocytes to undergo morphological changes that enable them to penetrate the vascular endothelium. Chemical signals from injured or infected tissues can also increase vascular permeability, easing leukocyte passage. Once through the endothelium, the leukocytes move towards sites of infection or inflammation, guided by chemotactic signals. This intricate process of leukocyte trafficking is critical for the body's immune response as it allows rapid deployment of immune cells to sites where they are needed most.