18 Questions
What is the normal range for platelets in the blood?
150-400x10^9/L
What is the main source of energy for platelets?
glucose
What is the average lifespan of platelets?
7-10 days (Rodak: 8-9 days)
What is the main stimulus for the production of platelets?
Thrombopoietin
What is the principal site for ATP synthesis in platelets?
Mitochondrion
Which organelle in platelets is responsible for storing small molecules that are endocytosed?
Dense body
What component of platelet protein constitutes 20% to 30% of the platelet cytoplasm?
Actin
Which organelle in platelets is responsible for digesting materials that are endocytosed by the platelets?
Lysosome
What is the role of FOG-1 and GATA-1 in megakaryocyte endomitosis?
Slows the transition from mitosis to endomitosis by preventing actin and myosin cytoskeleton and cytokinesis
What is the significance of 128N in megakaryocyte biology?
Indicates a hematologic disease
Describe the characteristics of a promegakaryocyte (MK-II) in the terminal differentiation phase.
Indention begins, abundant cytoplasm with few fine azurophilic granules, more developed demarcation system
What are the key features of a megakaryocyte (MK-III) in the terminal differentiation phase?
Intense indentation and lobulation, lobulated nucleus, basophilic chromatin pattern, visible and defined demarcation system, azurophilic and granular, platelet shedding, alpha and dense granules
What is the function of the Open canalicular system in platelets?
Enhances platelet interaction with its environment. Route for endocytosis and secretion of alpha granules upon activation.
What is the role of Von Willebrand Factor (VWF) in platelet adhesion?
VWF is stored in Weibel palade bodies and serves as a substrate for platelet adhesion.
How is platelet and VWF regulated?
Platelet and VWF is regulated by ADAMTS-13 (VWF cleaving protease).
What happens at high shear rates in platelets?
At high shear rates, platelets bind to collagen via GP VI, triggering an internal platelet activation pathway.
What is the consequence of the 'outside-in-reaction' in platelets?
The release of ADP and TXA2, which are potent vasoconstrictors.
What is the result of the 'inside-out' reaction in platelets?
It causes an increase in the affinity of integrin a2B1 for collagen, platelet shape change, and activation of neighboring platelets.
This quiz covers the components of the platelet cytoskeleton, including microfilaments, intermediate filaments, and submembranous cytoskeleton. It focuses on the roles of actin, tubulin, desmin, vimentin, and myosin in maintaining platelet shape and enabling alpha granule expression.
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