A white blood cell that has a single nucleus and can ingest (take in) foreign material. (In other words, a monocyte is thus a mononuclear phagocyte that circulates in the blood.) Monocytes later emigrate from blood into the tissues of the body and there differentiate (evolve into) into cells called macrophages which play an important role in killing of some bacteria, protozoa, and tumor cells, release substances that stimulate other cells of the immune system, and are involved in antigen presentation.
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A relatively large mononuclear leukocyte (16–22 μm in diameter), that normally constitutes 3–7% of the leukocytes of the circulating blood, and is normally found in lymph node s, spleen, bone marrow, and loose connective tissue. When treated with the usual dyes, monocytes manifest an abundant pale blue or blue-gray cytoplasm that contains numerous, fine, dustlike, red-blue granules; vacuoles are frequently present; the nucleus is usually indented, or slightly folded, and has a stringy chromatin structure that seems more condensed where the delicate strands are in contact. SEE ALSO: monocytoid cell, endothelial leukocyte. [mono- + G. kytos, cell]

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mono·cyte 'män-ə-.sīt n a large white blood cell with finely granulated chromatin dispersed throughout the nucleus that is formed in the bone marrow, enters the blood, and migrates into the connective tissue where it differentiates into a macrophage
mono·cyt·ic .män-ə-'sit-ik adj
mono·cyt·oid -'sīt-.ȯid adj

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a variety of white blood cell, 16-20 µm in diameter, that has a kidney-shaped nucleus and greyish-blue cytoplasm (when treated with Romanowsky stains). Its function is the ingestion of foreign particles, such as bacteria and tissue debris. There are normally 0.2-0.8 x 109 monocytes per litre of blood.
monocytic adj.

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mono·cyte (monґo-sīt) [mono- + -cyte] a mononuclear phagocytic leukocyte, 13 to 25 μm in diameter, with an ovoid or kidney-shaped nucleus, containing lacy, linear chromatin and abundant gray-blue cytoplasm filled with fine reddish and azurophilic granules. Formed in the bone marrow from promonocytes, monocytes are transported to tissues such as the lung and liver, where they develop into macrophages. See also monocytic series, under series.

Medical dictionary. 2011.

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