Leukocytes, or white blood cells as they are more commonly known, are a major part of the body's immune system. These round, large cells have no nuclei and contain no haemoglobin. There are five different types of blood cells and each has a specific function. The granulocytes, which have granules in the cytoplasm are the neutrophil, the basophil and the eosiniphil. Agranulocytes, those leukocytes without granules are the lymphocytes and monocytes.
This is the most common granulocyte, accounting for more than half of the total amount of white blood cells. They have incredibly short lifespans, remaining in the blood for only about 12 hours. These cells work hard to perform phagocytosis, the engulfing of and destroying of debris and pathogens. After battling an infection, dead neutrophils are left behind with a mixture of fluid and other cell parts that is called pus. Neutrophils are essential and a deficiency of them is considered life threatening.
Basophils are usually present in much smaller numbers than neutrophils. They account for less than 1% of the total white blood cells. They are known to play a role in releasing histamine during a response to inflammation. They also release the anticoagulant heparin. Basophils are usually found in areas such as the lungs and the liver, where there is a large volume of blood, and it's possible that the heparin they release helps prevent tiny blood clots from forming.
Eosinophils are responsible for 1-3% of leukocytes. While much is not known about them, it is clear that they are involved in the body's response to inflammation. Eosinophils release chemicals that can destroy pathogens. A person who is in the midst of an allergic reaction will have an increased number of eosinophils in their bloodstream, as will a person who is fighting an infection of a parasitic nature.
Lymphocytes make up between 25 -- 38 % of all leukocytes. Lymphocytes play a huge part in the body's immune system. There are two subdivisions of lymphocytes, B-lymphocytes and T-lymphocytes. B-lymphocytes are created In the bone marrow, while T-lymphocytes are generated from the thymus gland. The main function of these cells is to create and release antibodies and to protect the body from cancer cells.
Monocytes, like neutrophils, can perform phagocytosis. They only account for 3 -- 8 % of all white blood cells, yet they are more efficient at destroying pathogens. These cells change into macrophages, which are able to leave the bloodstream and enter body tissue. Monocytes then patrol the body looking for pathogens and debris to clean up. Macrophages are common in the mucus membranes and under the skin, where they can be readily available to fight anything that invades the body through a small tear or scratch. These cells provide another service to the body; they phagocytose old red blood cells, helping the bloodstream remain healthy.