Platelets are one of the many key components of the blood necessary for normal functioning of the body. It is a highly significant constituent in the control of bleeding and prevention of the loss of blood which is only possible with platelet plug formation and blood clotting.
This cellular component of the blood is formed in the bone marrow. The bone marrow is a location where all blood components are formed through stem cells which have the capacity to divide endlessly and become converted into several types of different cellular lines.
Megakaryocyte and platelet production is regulated by thrombopoietin. This is a hormone produced in the kidneys and liver.
There are two types of bone marrow; namely, the red and the yellow marrow. The red marrow is where blood cells are formed. Read Platelets and Blood Clotting.
Ten-Step Platelet Formation
We have below the following steps to detail platelet formation from birth to disposition:
1. The first cell.
When an embryo is born, it consists a type of cell called totipotent cell. Totipotent cells are capable of dividing into any cell of the body, be it bone or brain, liver or lung, and eye or ear. This cell gives rise to all the cells with an unmatched capacity to divide. It forms the hematopoietic cells which then give birth to all the cells of the blood. These stem cells keep on dividing to keep the pool of totipotent cells alive.
2. Birth mother of all blood cells.
The first ancestors in the blood line of cells having the lineage of platelets are hematopoietic stem cells. These stem cells are pleuripotent, which means that they can grow into any form of blood cell lines including red blood cells, white blood cells, and platelets. This is the first cell that gives birth to all other cells in the blood.
Hematopietic cells give birth to progenitor cells under the influence of colony-stimulating factors which require chemicals to direct a particular type of cell to divide into another particular type of cell. For example, the GM-CSF or granulocyte monocyte colony stimulating factor gives rise to blood cell lines from hematopietic cells. These cells also keep on dividing to keep the pleuripotent pool alive.
3. The progenitor cells.
Progenitor cells are the committed cell types in this lineage. Once formed, they can only give rise to the next cell line depending on the chemical influence provided.
This is to say that the progenitor cells are committed to form the given cell type and will not form any other cell type. One type of progenitor cell will only ever give rise to a particular cell type.
4. Pooling of the cell lines.
These different types of cell lines form together from a common ancestor. The cell lines pool in their respective areas and separate from one another.
The progenitor cells form the megakaryoblast under the stimulating effect of colony-stimulating factors. These factors are an essential requirement for the formation of platelets. Megakaryobasts are immature cells and found only in the bone marrow.
In certain type of diseases, these cells are released early into the circulation and can be seen on a peripheral blood smear.
6. Megakaryocyte formation.
The megakaryoblasts mature under the effect of the same colony-stimulating factors to give rise to megakaryocyte. The role of colony-stimulating factors in the formation of platelets is limited to this step. Erythropoietin takes the task in the formation of platelets from here.
7. Megakaryocyte maturation.
Megakaryocytes mature under the influence of erythropoietin. Erythropoietin is formed by the liver and kidneys which is released into the blood from where it reaches the bones and enters the bone marrow. This is where it displays its influence in the maturation of megakaryocytes.
In diseases involving the liver and kidneys where erythropoietin production is compromised, the number of platelets may drop due to the lack of optimization in this step.
8. Megakaryocyte extrusion from bone.
Megakaryocytes are the precursors of platelets. This is the last step with regards to the involvement of the bone marrow from all the other further steps that takes place outside the bone and in the blood. Megakaryocytes are extruded from the bone through the capillaries and released into the blood.
9. Megakaryocyte breakage and proplatelet release.
Nuclear death and cellular breakage occurs as soon as the megakaryocytes are released into the blood and even as they are being released into the blood through the capillaries. The megakaryocytes at this stage have proplatelet outgrowths which break off from the main body of the megakaryocytes. These proplatelet extensions carry with them the protein forming machinery of the cells.
Platelets are finally formed from the breaking off of proplatelets into further smaller pieces in the blood. These platelets can be counted in the blood though diagnostic procedures like taking a blood sample from the peripheral blood and putting it in a cell counter. The procedure is helpful in detecting any abnormally high or abnormally low number of platelets.
In order to take a look at platelet morphology, a peripheral blood smear is made and observed under a microscope. A smear is a spread of blood taken from a periphery (such as the limb) and spread on a slide.
Platelet formation as summarized into these basic ten steps suggest that a lot may possibly go wrong which can affect platelet count or morphology. Any defect or drug that interferes with just one of these steps may lead to an alteration in the platelet formation process resulting to abnormal number, growth, and/or structure of platelets.
In order to diagnose a patient who presents symptoms suggestive of platelet dysfunction such as bleeding or clotting, a physician has to take into account all these steps and examine each step for factors that may have affected the platelet count. This means combination in the assessment of symptoms, diagnostic examinations, and results of platelet count and morphology.
It is important to note that all the blood cells originate from a single cell. In fact, all cells originate from a single cell and a defect at an early stage may present a disease at a much later stage. Therefore, at the time of platelet formation, which continues throughout life, it is important for the bone marrow to be kept safe. A small change in the environment of platelet formation, or production process of any other blood cell, can result to a huge difference in the normal functioning of the body.
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