Sketch of bone marrow and its cells

Pluripotential hemopoietic stem cells (PHSCs) are stem cells found in the bone marrow. They are called pluripotential because these cells have the ability to differentiate into any of several types of blood cells. Hemopoiesis is the formation of blood cellular components. Mouse embryonic stem cells. ... Haematopoiesis is the formation of blood cellular components. ...

Background

The existence of these cells were determined by clever experiments on animals. Bone marrow cells are extracted from an animal, which is then subjected to radiation. This destroys any bone marrow cells. Once this is accomplished, the previously collected cells are then injected into the blood stream and eventually make their way into the spleen (which has a similar environment as bone marrow for hemopoiesis). The cells multiply and form colonies, which contain only certain types of blood cell or blood cell precursors. These cells are defined as colony-forming units (CFU). Bone marrow is the tissue comprising the center of large bones. ... Radiation generally means the transmission of objects or information from a source into a surrounding medium or destination. ... The spleen is a ductless, vertebrate gland that is not necessary for life but is closely associated with the circulatory system, where it functions in the destruction of old red blood cells and removal of other debris from the bloodstream, and also in holding a reservoir of blood. ...

Colony-forming units

There are four kinds of colony-forming units:

• Colony-forming unit erythrocyte (CFU-E)
• Colony-forming unit granulo-monocyte (CFU-GM)
• Colony-forming unit lymphocyte (CFU-L)
• Colony-forming unit megakaryocyte (CFU-Me)

Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ...

CFU-E

These cells are precursors for red blood cells, or erythrocytes. The process of red blood cell formation is called erythropoiesis. Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ... Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ... Erythropoiesis is the process by which red blood cells (erythrocytes) are produced. ...

The cell differentiates as follows:

• Proerythroblast
• Polychromatophilic erythrocyte
• Normoblast
• Erythrocyte

CFU-GM

These cells are precursors for granulocytes (basophil, eosinophil, neutrophil) or monocytes. The processes of cell formation are called granulocytopoiesis and monocytopoiesis Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. ... Categories: Wikipedia cleanup | Biology stubs | Blood and immune system cells ... Eosinophils are white blood cells that are responsible for combating infection by parasites in the body. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ...

The granulocyte precursor cell differentiates as follows: Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. ...

• Myeloblast
• Promyelocyte
• Eosino/neutro/basophilic myelocyte
• Eosino/neutro/basophil

The monocyte precursor cell differentiates as follows: A monocyte is a white blood cell, part of the human bodys immune system. ...

• Promonocyte
• Early monocyte
• Monocyte

CFU-L

These cells are precursors for lymphocytes. The process of lymphocyte formation is called lymphocytopoiesis. A lymphocyte is a type of white blood cell involved in the human bodys immune system. ...

The cell differentiates as follows:

• Lymphoblast
• Prolymphocyte
• Large lymphocyte
• Small lymphocyte

Prolymphocyte that released into the blood stream and travel to the spleen or lymph nodes differentiate into B-lymphocytes and those that travel into the thymus differentiate into T-lymphocyte. The spleen is a ductless, vertebrate gland that is not necessary for life but is closely associated with the circulatory system, where it functions in the destruction of old red blood cells and removal of other debris from the bloodstream, and also in holding a reservoir of blood. ... Lymph nodes are components of the lymphatic system. ...

CFU-Me

These cells are precursors for megakaryocytes, which later form blood platelets or thrombocytes. The process of thrombocyte formation is called thrombocytopoiesis. The megakaryocyte is a bone marrow cell responsible for the production of blood platelets when cytoplasm processes become fragmented. ... ...

The cell differentiates as follows:

• Megakaryoblast
• Promegakaryocyte
• Megakaryocyte

Platelets are then formed from the fragmentation of the megakaryocyte cytoplasm. The megakaryocyte is a bone marrow cell responsible for the production of blood platelets when cytoplasm processes become fragmented. ... Cytoplasm is the viscid, semi-fluid matter contained within the plasma membrane of a cell that helps to hold the cell together. ...

Nomenclature

Between 1948 and 1950, the Committee for Clarification of the Nomenclature of Cells and Diseases of the Blood and Blood-forming Organs issued reports on the nomenclature of blood cells. An overview of the terminology is shown below, from earliest to final stage of development:

• [root]blast
• pro[root]cyte
• [root]cyte
• meta[root]cyte
• mature cell name

The root for CFU-E is "rubri", for CFU-GM is "granulo" or "myelo" and "mono", for CFU-L is "lympho" and for CFU-Me is "megakaryo". According to this terminology, the stages of red blood cell formation would be: rubriblast, prorubricyte, rubricyte, metarubricyte and finally erythrocyte. . The nomenclature used in the article seems to be, at present, the most prevalent.

Physical Characteristics

The physical characteristic of each stage of a cell's development is somewhat subjective but usually specific. However, since there is no consensus on the number of stages in the development of any given cell, it would be difficult to attribute characteristics since it may not apply across all systems being used. For instance, characteristics that define a metamyelocyte could be considered either the mature cell or a myelocyte in the system used in this article.

However, general trends can be observed as the cell matures:

• Size of the cell and nucleus gradually shrinks
• Ratio of nucleus to cytoplasm decreases
• Color of the nucleus becomes darker
• Nucleoli disappears
• Shape of the nucleus changes from round to irregularly shaped

These are only general guidelines which may not all apply to every cell. A notable exception is the mature lymphocyte, which generally keeps a round nucleus.