Leukocyte life: time in circulating blood and tissue

2021-05-07 11:51 PM

The life of leukocytes after leaving the bone marrow is usually 4-8 hours in circulating blood and about 4-5 days in the tissues that need them. In severe tissue infections, life is often shortened to only a few hours.

Our bodies are constantly exposed to bacteria, viruses, fungi, and parasites, most of which are non-pathogenic and vary in skin, mouth, respiratory tract, intestinal tract, eye membranes, and even the gastrointestinal tract. urinary. Many infectious agents can cause serious physiological abnormalities or even death if they penetrate deeply into the tissues. We may also be intermittently exposed to highly infectious bacteria and viruses that are not among the normal types on the body, and these agents can cause fatal acute illness. such as pneumonia, streptococcal infection and typhoid fever.

Our bodies have a special system for killing various infectious and poisoning agents. This system consists of leukocytes (WBCs) and leukaemia-derived cells. These cells work together in two ways to treat disease: (1) actually killing bacteria and viruses that invade by phagocytosis and (2) generating antibodies and increasing susceptibility to these pathogens. lymphocytes can destroy or inactivate the invading agent. This chapter is concerned with the first method and chapter 35 will talk about the second method.

White blood cells (leukocytes / white blood cells) are cell units of the body's protective system. They are produced partly in the bone marrow (granulocytes and monocytes and some lymphocytes) and partly in lymphoid tissue (lymphocytes and cytoplasm). Once formed, they are transported into the bloodstream to different places in the body where they are needed.

The practical value of WBCs is that most of them are visibly transported to areas with severe infections and inflammatory foci, thereby providing quick and powerful protection against the infectious agent. As we will see later, granulocytes and monocytes have a special ability to "find and destroy" a foreign agent.

The life of leukocytes after leaving the bone marrow is usually 4-8 hours in circulating blood and about 4-5 days in the tissues that need them. In severe tissue infections, life is often shortened to only a few hours as the granulocytes continually reach the site of the infection faster, perform their function, and in the process, themselves suffer. destroy.

Monocytes also have a short transport time, 10-20 hours in the blood, before passing through the capillary membrane into tissues. Once in tissue, they swell in size to become tissue macrophages, and in this form, they can live for months unless destroyed while performing a phagocytic function. These tissue macrophages are the basis of the system of tissue macrophages (discussed in more detail later), further providing protection against infection.

Lymphocytes continuously enter the circulatory system, throughout the lymphatic vessels from the lymph nodes and other lymphoid tissues. After a few hours, they leave the haemostasis and return to the tissues with diapedesis. Then they return to the lymphatic vessels, then back into the bloodstream and so on; it is the constant circulation of lymphocytes in the body. Lymphocytes have a life of several weeks or months, depending on the needs of the body.

Platelets in the blood are replaced about every 10 days, about 30,000 platelets are formed every day in each microlite of blood.


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