Many people may be familiar with the name of white blood cells, but what exactly are they? What functions do they have? This article will answer the questions about these tiny security guards of our bodies.

White blood cells, or WBCs, are an important part of your immune system. They are vital to the body because they fight infection, thus knows as the security guards of bodies. WBCs are colorless, nucleated cells, spherical in shape, 7-25 microns in diameter.

Like other blood cells, the production and regulation of WBCs originate from hematopoietic stem cells in the bone marrow. The transition from hematopoietic stem cells to mature WBCs is not an instantaneous change, but a process with several stages. They first upgrade from hematopoietic stem cells to directed progenitor cells, and then upgrade to identifiable precursor cells.

WBCs are a heterogeneous group of nucleated cells. Physiologically, they are divided into three subgroup, granulocytes, monocytes and lymphocytes according to their morphology, function and source. Different types of white blood cells participate in the body's defense response in different ways.

Monocytes enter the tissues after 2 to 3 days in the circulating blood and continue to develop into macrophages. The new form allows them to survive in the tissues for about 3 months.

Lymphocytes are mainly involved in the immune response of the body. Under normal circumstances, lymphocytes have a long life span. They travel between blood, tissue fluid, and lymph fluid, and can proliferate and differentiate in lymph nodes and other places, demonstrating their strong resistance.

Granulocytes occupy the most important position in white blood cells and can be divided into three types—neutrophils, eosinophils, and basophils.

Among them,neutrophils have obvious effects on the human body as they can effectively kill bacteria. Generally speaking, neutrophils stay in the circulating blood for about 8 hours and then enter the tissues, and die after 4-5 days, or are discharged from the gastrointestinal tract through the mucosa of the digestive tract. When bacteria invade the human body, it may cause inflammation in a certain part. At this time, neutrophils are like brave warriors, quickly marching to the inflammation site and wrapping the bacteria one by one.

This process is called phagocytosis. In the process of phagocytic, granulocytes will use enzymes to break down bacteria, so that the bacteria can no longer attack the human body and cause inflammation. When excess lysosomal enzymes are released by granulocytes, they will self-dissolve and eventually form pus together with the killed bacteria and tissue fragments.

There is always a blood test during routine physical examinations. Many people may have encountered a situation where the number of WBCs is lower than the normal showing on the report. There are many reasons for the low number of WBCs.

Firstly, the production is reduced. WBCs have a certain life span. Human bodies are producing them all the time, and at the same time, some of them are constantly dying. If the production of WBCs is reduced, it will lead to a decrease in the total amount. For example, hematopoietic bone marrow, leukemia, even malnutrition, can lead to the reduction of hematopoietic raw materials. The second reason may be that they are destroyed or consumed too much. For example, toxic chemicals, radiation, as well as chemotherapy can kill many of them. In severe infections, WBCs will also be consumed.

The reduction of WBCs can cause weakness, fatigue, muscle aches, dizziness. Severe infections of the respiratory tract, digestive tract and other organs may also occur, manifested as high fever, cough, expectoration, abdominal pain, diarrhea, even poisoning and shock. Therefore, if there is an abnormality in any part of body or in physical examination data, one should better seek medical treatment in time.