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Neutrophils Functions & Origin

Presentation Notes on Neutrophils Origination & Roles in Blood of a Human body  for Kids & Students of Biology & Medical in word / .ppt/ . pdf format 

Functions:-

Most important function of the neutrophil is to attack and destroy the invading bacteria. If and when bacteria enter the body (say, via a breach in the skin/mucous mem­brane), there develops an inflammation. this inflammation produces some effects  by which the neutrophils emigrate then they move towards the bacteria (chemotaxis) catch hold the bacteria and pha­gocytose them digest them by their primary lysosomal granular contents. Thus they eliminate the bacteria. For emigration , chemotaxis , phagocytosis, the neutrophil has to move and this movement is produced by pseudopods. Neutrophils thus can throw pseudopods by causing contraction of their actin."

Note. (1) Red bone marrow pool serves as reservoir of the neutrophils. (2) Besides the neutrophil the macrophages are also phagocytic. Hence neutrophils are called 'micro­phages'. (3) Neutrophils are like those soldiers which are ordered to attack the invading bacteria immediately,hence the neutrophils constitute, "the first line of defence against bacteria".

Origin:-

The neutrophils arise, in the RBM (red bone marrow),from the stem cell, called, pluripotent stem cell which becomes the committed stem cell and ultimately becomes CFU-GM (colony forming unit, granulocyte­-monocyte). The pluripotent stem cell/ committed stem cell/ CFU-GM are not visible under Leishman's stain. The CFU­GM can produce myeloblasts or monoblasts. From myeloblasts (strictly speaking, these should be called neutrophilic myeloblasts) the mature neutrophils develop. Myeloblasts are the first recognizable cell by Leishman's stain. Normally myeloblasts are seen only in the RBM but not in the peripheral blood but abnormally (eg, in acute leukemia) myeloblasts can be seen in the peripheral blood too.

The stages from myeloblast to mature neutrophil are: myeloblast (nucleus large and contains 1 to 5 nucleoli, cytoplasm is bluish because of its large RNA content but the cytoplasm contains no granules) promyelocyte (only one nucleolus, cytoplasm contains primary granules) myelocyte (the nucleus is indented, cytoplasm abundant containing pink staining granules; nucleolus absent) metamyelocyte (nucleus indented, cytoplasm contains large number 2nd ary granules) band form (nucleus horse shoe shaped) mature neutrophil. Now, the young neutrophil enters the peripheral circulation.

Factors influencing neutrophil development and release into the circulation:

On an average, an adult person loses about 1.0 x 1011 neutrophils a day. In health, the production and release of the neutrophils are so fineiy regulated that (i) daily loss is replenished and (ii) the blood neutrophil count is constant However in diseased states the blood neutrophil count can alter. The production of neutrophils is influenced by hemo­poietic growth factors.

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