Megakariocytów

Megakariocytów, also known as megakaryocytes, are large, multinucleated bone marrow cells. They are the largest cells in the bone marrow, typically ranging from 40 to 100 micrometers in diameter. Their primary function is the production of platelets, also known as thrombocytes. This process is called thrombopoiesis.

Megakaryocytes originate from hematopoietic stem cells and undergo a complex differentiation process. This process involves endomitosis, where the cell replicates its DNA without undergoing cell division, leading to a polyploid nucleus. The cytoplasm of the megakaryocyte becomes increasingly granular and develops specialized structures called proplatelets.

These proplatelets are long, thin cytoplasmic extensions that extend into the bloodstream or sinusoids of the bone marrow. Small fragments, which are essentially platelets, then bud off from the tips of these proplatelets. Each megakaryocyte can produce thousands of platelets.

The regulation of megakaryocyte development and platelet production is primarily controlled by the hormone thrombopoietin, which is produced mainly by the liver. Thrombopoietin binds to receptors on megakaryocyte precursor cells and megakaryocytes, stimulating their proliferation, differentiation, and maturation.

Megakaryocytes are found in the red bone marrow of long bones, vertebrae, and the sternum in adults. Their morphology and number can vary depending on physiological states, such as infection or bleeding, and in certain pathological conditions. Abnormalities in megakaryocyte development can lead to conditions characterized by either a deficiency (thrombocytopenia) or an excess (thrombocytosis) of platelets.