Platelets and Megakaryocytes Quiz

Origin of Platelets

• Platelets originate from megakaryocytes, large bone marrow cells that undergo a process called thrombopoiesis.
• Megakaryocytes extend their cytoplasmic processes into the bloodstream, where fragments are released as platelets.

Mechanism of Cessation of Bleeding

• The cessation of bleeding involves vasoconstriction, the formation of a platelet plug, and the activation of the coagulation cascade.
• Platelets adhere to the exposed collagen at the site of injury, activating and releasing chemical signals that recruit more platelets.

Function of Platelets in Primary Hemostasis

• Platelets are crucial for primary hemostasis by aggregating at the injury site to form a temporary plug.
• They release various substances, including ADP and thromboxane A2, which promote further platelet activation and aggregation.

Substance Formed in the Coagulation Cascade

• The ultimate substance formed in the coagulation cascade is fibrin, which stabilizes the platelet plug and forms a solid blood clot.
• Fibrinogen, a plasma protein, is converted to fibrin through the action of thrombin during the cascade.

Origin of Megakaryocytes

• Megakaryocytes are derived from hematopoietic stem cells in the bone marrow.
• They differentiate and mature through various stages and are stimulated by thrombopoietin, a hormone that regulates platelet production.