átfrumur

Átfrumur, also known as phagocytes, are a type of white blood cell that plays a crucial role in the immune system. Their primary function is to engulf and digest foreign materials, cellular debris, and pathogens such as bacteria and viruses. The word "phagocyte" originates from the Greek words "phagein" meaning "to eat" and "kytos" meaning "cell," accurately describing their engulfing nature.

There are two main types of phagocytes: granulocytes and mononuclear phagocytes. Granulocytes include neutrophils and eosinophils, which are typically the first responders to infection. Neutrophils are abundant and are key in combating bacterial infections. Eosinophils are more involved in fighting parasitic infections and allergic responses. Mononuclear phagocytes include monocytes and macrophages. Monocytes circulate in the bloodstream and can differentiate into macrophages when they migrate into tissues. Macrophages are larger and longer-lived than neutrophils and are crucial for both acute and chronic inflammatory responses, as well as antigen presentation to other immune cells.

The process of phagocytosis involves several steps. First, the phagocyte recognizes and binds to the target particle. This recognition can be direct or mediated by opsonins, which are molecules that coat the target, making it more easily recognized. The phagocyte then extends its cell membrane to engulf the particle, forming a vesicle called a phagosome. This phagosome fuses with lysosomes, which contain digestive enzymes and reactive oxygen species, to form a phagolysosome. Within the phagolysosome, the engulfed material is broken down and neutralized. Undigested material can be expelled from the cell.