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Unlike red blood cells, leukocytes (white blood cells) have a nucleus and can move independently. They are highly differentiated for their specialized functions and do not undergo cell division (mitosis) in the blood, although some retain the ability to undergo mitosis. As a group, they participate in the body’s defense mechanisms and repair activities. The number of white blood cells in normal blood ranges from 4,500 to 11,000 per cubic millimeter. Fluctuations occur during the day; lower values ​​are obtained while resting and higher values ​​are obtained while exercising. Severe physical exertion may result in counts exceeding 20,000 per cubic millimeter. Most white blood cells are outside the circulation, and a few in the blood are transported from one site to another. As living cells, their survival depends on their constant production of energy. The chemical pathways utilized are more complex than those of red blood cells and similar to those of cells in other tissues. White blood cells contain nuclei that produce ribonucleic acid (RNA) and can synthesize proteins. They are composed of three types of cells, each unique in structure and function, called granulocytes, monocytes, and lymphocytes.

What Is The Main Function Of White Blood Cells

Granulocytes are the most numerous white blood cells and are larger than red blood cells (approximately 12-15 μm in diameter). They have multilobed nuclei and contain numerous cytoplasmic granules (i.e., granules in the cellular material outside the nucleus). Granulocytes are important mediators of the inflammatory response. There are three types of granulocytes: neutrophils, eosinophils, and basophils. When cells are stained with complex dyes, each type of granulocyte can be identified by the color of the granules. The particles of neutrophilic spheres are pink, the particles of eosinophilic spheres are red, and the particles of basophilic spheres are blue-black. About 50 to 80 percent of white blood cells are neutrophils, while eosinophils and basophils combined make up no more than 3 percent.

Red Blood Cells: Function And Structure

Neutrophils are fairly uniform in size, ranging from 12 to 15 μm in diameter. The nucleus consists of two to five lobes connected together by hair-like filaments. Neutrophils move with amoebae. They project long protrusions called pseudopods into which particles flow. Then, filaments in the cytoplasm contract, pulling the nucleus and the back of the cell forward. In this way, neutrophils rapidly advance along the surface. The bone marrow of a normal adult produces approximately 100 billion neutrophils per day. It takes about a week to form mature neutrophils from precursor cells in the bone marrow; however, once in the bloodstream, mature cells only survive for a few hours or possibly a little longer after migrating to tissues. To prevent rapid depletion of short-lived neutrophils (e.g., during infection), the bone marrow reserves large numbers of neutrophils for mobilization in times of inflammation or infection. In the body, neutrophils migrate to areas of infection or tissue damage. The attractive force that determines the direction of neutrophil movement is called chemotaxis and is attributed to substances released at the site of tissue damage. Of the 100 billion neutrophils circulating outside the bone marrow, half are in tissues and half in blood vessels. In blood vessels, half is in the fast-circulating blood mainstream, and the other half moves slowly along the inner wall of the blood vessel (marginal pool), preparing to enter the tissue after receiving chemotactic signals from the tissue.

Neutrophils have active phagocytic capabilities; they engulf bacteria and other microorganisms as well as tiny particles. The particles of neutrophils are tiny packets of powerful enzymes capable of digesting many types of cellular material. When a bacterium is engulfed by a neutrophil, it becomes enclosed in a vacuole lined by an invaginated membrane. The particles discharge their contents into vacuoles that contain organisms. When this occurs, neutrophil granules are depleted (degranulated). Metabolic processes within the granules produce hydrogen peroxide and highly reactive oxygen species (superoxide), which destroy ingested bacteria. Final digestion of invading organisms is accomplished by enzymes.

Like other granulocytes, eosinophils are produced in the bone marrow until released into the circulation. Although approximately the same size as neutrophils, eosinophils contain larger granules and chromatin is typically concentrated in only two unsegmented lobes. Eosinophils leave the circulation within hours after being released from the bone marrow and migrate through lymphatic vessels to tissues (usually the skin, lungs, and respiratory tract). Like neutrophils, eosinophils respond to chemotactic signals released at sites of cell destruction. They have active motility and phagocytic abilities. Eosinophils are involved in defense against parasites and in allergic and inflammatory responses, primarily by inhibiting their damaging effects.

Basophilic spheres are the least numerous of the granulocytes, and their large granules almost completely obscure the underlying bilobed nucleus. Within hours after release from the bone marrow, basophils migrate from the circulation to barrier tissues such as skin and mucous membranes, where they synthesize and store histamine, a natural regulator of the inflammatory response. When the condition worsens, basophils release leukotrienes along with histamine and other substances that cause bronchoconstriction during an allergic reaction (anaphylaxis). Basophils cause an immediate allergic reaction involving platelets, macrophages, and neutrophils.

Solution: Functions Of Blood(corpuscles)

Monocytes are the largest cells in the blood (average diameter 15-18 μm), accounting for approximately 7% of white blood cells. The nuclei are relatively large and tend to be serrated or folded rather than leafy. The cytoplasm contains a large number of fine particles, and particles close to the cell membrane tend to be more numerous. Monocytes have active motility and phagocytic capabilities. They are able to ingest infectious agents as well as red blood cells and other large particles, but they cannot replace the function of neutrophils in clearing and destroying bacteria. Monocytes generally enter areas of inflamed tissue later than granulocytes. They usually appear at sites of chronic infection.

In the bone marrow, granulocytes and monocytes are generated from common precursors under the influence of granulocyte-macrophage colony-stimulating factor. Monocytes leave the bone marrow and circulate in the blood. After a few hours, the monocytes enter the tissue, where they develop into macrophages, the tissue-phagocytic cells that make up the reticuloendothelial system (or macrophage system). Macrophages are found in nearly all tissues of the body. The cells in the liver are called Kupffer cells and the cells in the skin are called Langerhans cells. In addition to their role as scavengers, macrophages also play a key role in immunity, taking up antigens and processing them so that lymphocytes recognize them as foreign substances.

Lymphocytes make up about 28-42% of the white blood cells in the blood, and they are part of the body’s immune response to foreign objects. Most lymphocytes are small, only slightly larger than red blood cells, and have a nucleus that occupies the majority of the cell. Some are larger and have a richer cytoplasm that contains some granules. Lymphocytes are slow moving and have different migration paths outside the bloodstream than granulocytes and monocytes. Lymphocytes are found in large numbers in lymph nodes, spleen, thymus, tonsils, and lymphoid tissue of the gastrointestinal tract. They enter the circulation through lymphatic channels, which drain primarily into the thoracic lymphatic vessels, which are connected to the venous system. Unlike other blood cells, some lymphocytes may leave and reenter the circulation and survive for about a year or longer. The main route of circulating lymphocytes is via the spleen or lymph nodes. Lymphocytes freely leave the blood and enter lymphoid tissue, passing through barriers that prevent other blood cells from passing through. When stimulated by antigens and certain other substances, some lymphocytes become activated and are able to undergo cell division (mitosis).

Lymphocytes regulate or participate in acquired immunity to foreign cells and antigens. They are responsible for generating immune responses to invading organisms, foreign cells (such as those from transplanted organs), as well as foreign proteins and other antigens that do not necessarily originate from living cells. These two types of lymphocytes are distinguished not by usual microscopic examination, but by the type of immune response they elicit. B lymphocytes, or B cells, are involved in what is called humoral immunity. When encountering foreign substances (or antigens), B lymphocytes differentiate into plasma cells and secrete immunoglobulins (antibodies). The second type of lymphocyte is the T lymphocyte (or T cell), which is involved in regulating the antibody-forming function of B lymphocytes and directly attacking foreign antigens. T lymphocytes participate in what is called cell-mediated immune responses. T lymphocytes are also involved in rejection of transplanted tissue and certain types of allergic reactions.

Foods To Boost White Blood Cells (immunity)

All lymphocytes begin development in the bone marrow. B lymphocytes partially mature in the bone marrow until released into the circulation. Further differentiation of B lymphocytes occurs in lymphoid tissue (spleen or lymph nodes), most notably

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