Monocytes are a type of white blood cell and are a part of the immune response system. The function of monocytes is to carry out the process of phagocytosis. During this process, large molecules found within the blood are ingested and then broken down. The two main purposes of phagocytosis are to protect the organism from attack by harmful pathogens, and to remove dead, dying or damaged cells from the blood.
When pathogens enter an organism, they cause an infection. In most cases, the pathogens are bacterial or viral cells. As the pathogens carry out their natural life processes, they produce and release chemicals. These chemicals attract white blood cells to the area of infection, including those that release antibodies and those that carry out phagocytosis. There are also proteins within the blood that attach to the bacteria or virus, which makes it easier for the cells of the immune system to recognize the pathogens.
The surface of a monocyte is not smooth as it has specific proteins on it that allow it to bind to the bacteria or virus cell. The function of monocytes is to move towards the specific pathogenic cell and eventually adhere to it when it is close enough. Attaching to the pathogen stimulates the production of a pseudopodium. This occurs due to the monocyte bending into a C shape around the pathogen, and the ends of the C meeting, so that the pathogen is engulfed.
The pathogen is then trapped within a phagosome inside of the monocyte. Engulfing the pathogen or dead or damaged cells is only one part of the function of monocytes. Once the cells or debris have been engulfed, they are broken down within the phagosome.
A lysosome is a type of cellular organelle that is found within the monocytes. When a phagosome is formed, the lysosomes attach to it and release digestive enzymes, called lytic enzymes, into the phagosome. These enzymes break down the cell within the phagosome, and the products that remain are absorbed by the monocyte.
Inflammation occurs at the site of the infection where phagocytosis occurs. The function of monocytes and other cells of the immune system causes the signs and symptoms associated with an inflammation. For example, heat and swelling are due to the activities of these cells. Moreover, pus is formed from the dead bacteria and the phagocytes, including monocytes, involved in fighting the infection.