Megakaryocytes

Megakaryocytes are large bone marrow cells that are responsible for the production of platelets, which are crucial for normal blood clotting. They are derived from hematopoietic stem cells and undergo a process known as endomitosis, where the cell undergoes multiple rounds of DNA replication without cell division, resulting in a large cell with a high number of chromosomes.

Structure

Megakaryocytes are among the largest cells in the bone marrow, with a diameter of up to 100 micrometers. They have a large, lobulated nucleus due to the process of endomitosis. The cytoplasm of megakaryocytes is abundant and contains granules that store proteins necessary for platelet function.

Function

The primary function of megakaryocytes is the production of platelets. This occurs through a process known as proplatelet formation, where long, branching processes extend from the megakaryocyte into the bone marrow sinusoids. These processes then fragment into platelets. Each megakaryocyte can produce thousands of platelets.

Clinical significance

Abnormalities in megakaryocytes can lead to a number of blood disorders. For example, in thrombocytopenia, there is a decrease in the number of platelets, which can be due to decreased production by megakaryocytes. In contrast, in thrombocytosis, there is an increase in the number of platelets, which can be due to increased production by megakaryocytes. Megakaryocytes are also involved in certain types of leukemia, where they can be abnormally large or small, or present in increased numbers.

See also

• Hematopoiesis
• Thrombopoietin
• Myeloproliferative neoplasms