megakarüotsüüdid

Megakarüotsüüdid are very large, multinucleated cells found in the bone marrow of mammals. They are precursors to platelets, which are small, irregular-shaped cell fragments essential for blood clotting. The formation of megakarüotsüüdid, a process known as megakarüotsütopoiesis, is a complex and tightly regulated process.

These cells originate from hematopoietic stem cells, which differentiate into megakaryocyte progenitor cells. These progenitors then undergo endomitosis, a process where DNA replication occurs without cell division, leading to the formation of a single, large cell with multiple sets of chromosomes and a characteristic multilobulated nucleus. The cytoplasm of megakarüotsüüdid is rich in granules containing various proteins and growth factors necessary for platelet production.

Mature megakarüotsüüdid are the largest cells in the bone marrow, often exceeding 50 micrometers in diameter. They extend long, thin cytoplasmic extensions called proplatelets into the bone marrow sinusoids. These proplatelets fragment into thousands of small, anucleated platelets that then enter the bloodstream. The size and number of megakarüotsüüdid can fluctuate depending on the body's demand for platelets. Conditions like thrombocytopenia, a low platelet count, can stimulate an increase in megakarüotsücyte production.