Platelet Activation and vWF in Blood

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Questions and Answers

Which components are involved in both hemostasis and thrombosis?

  • Endothelial cells, platelets, factors of the coagulation cascade (correct)
  • Red blood cells, white blood cells, plasma proteins
  • Antibodies, antigens, lymphocytes
  • Hemoglobin, fibrinogen, albumin

What is the main difference between hemostasis and thrombosis?

  • Size of the blood clot
  • Location of blood clot formation (correct)
  • Speed of blood clot formation
  • Color of the blood clot

What does hemostasis maintain besides homeostasis?

  • Blood pH balance
  • Electrolyte concentrations
  • Blood fluidity (correct)
  • Oxygen levels in the blood

What happens when the delicate balance between pro and anti-thrombotic activities of blood is destroyed?

<p>Excessive bleeding or thrombosis (A)</p> Signup and view all the answers

Which factor is activated by thrombin and is involved in the cross-linking of fibrin?

<p>Factor XIII (C)</p> Signup and view all the answers

What is the major function of plasmin?

<p>Fibrinolysis and inhibition of fibrin polymerization (D)</p> Signup and view all the answers

Which molecule is a potent inhibitor of platelet adhesion and aggregation, as well as a vasodilator?

<p>Prostacyclin (PGI2) (D)</p> Signup and view all the answers

Which molecule binds thrombin, inhibiting its activity, and then forms a complex to inhibit protein C?

<p>Thrombomodulin (B)</p> Signup and view all the answers

Which plasminogen activator is synthesized principally by endothelium and is most active when bound to fibrin?

<p>Tissue-PA (B)</p> Signup and view all the answers

What is the additional function of thrombin apart from its involvement in the coagulation cascade?

<p>Activation of Proteases Activated Receptors (PARs) (B)</p> Signup and view all the answers

What are the major functions of plasmin?

<p>Fibrinolysis and inhibition of fibrin polymerization (A)</p> Signup and view all the answers

Which molecule inhibits platelet adhesion and aggregation as well as acts as a vasodilator?

<p>Prostacyclin (PGI2) (B)</p> Signup and view all the answers

Which molecule binds thrombin, inhibiting its activity, and then forms a complex to inhibit protein C?

<p>Thrombomodulin (B)</p> Signup and view all the answers

Which plasminogen activator is synthesized principally by endothelium and is most active when bound to fibrin?

<p>Tissue-PA (D)</p> Signup and view all the answers

What is the central event in the coagulation cascade?

<p>Conversion of factor X into Xa (A)</p> Signup and view all the answers

Which molecule is responsible for platelet adhesion to the vessel wall?

<p>Adhesion molecules (C)</p> Signup and view all the answers

What is the role of phosphatidyl serine in platelet activation?

<p>Binding prothrombin and activating the coagulation cascade (C)</p> Signup and view all the answers

Which factor is crucial for the conversion of fibrinogen into fibrin and the cross-linking of fibrin fibers?

<p>Thrombin (D)</p> Signup and view all the answers

What do activated platelets release to aid in hemostasis?

<p>$ ext{PDGF}$ (B)</p> Signup and view all the answers

What is the primary function of fibrinogen in hemostasis?

<p>Platelet aggregation and clot formation (B)</p> Signup and view all the answers

How do platelets adhere to the vessel wall?

<p>Through adhesion molecules (C)</p> Signup and view all the answers

Which molecule plays a significant role in factor X activation?

<p>Calcium ions (D)</p> Signup and view all the answers

What flips out to the outer membrane of activated platelets and plays a role in activating the coagulation cascade?

<p>Phosphatidyl serine (C)</p> Signup and view all the answers

Which enzyme is crucial for converting fibrinogen into fibrin and cross-linking fibrin fibers?

<p>Thrombin (A)</p> Signup and view all the answers

What plays a crucial role in orchestrating hemostasis through factors production and binding of platelets to broken endothelium?

<p>Endothelial cells (C)</p> Signup and view all the answers

Which molecule activates Antithrombin III?

<p>Heparin-like molecules on endothelial cells (B)</p> Signup and view all the answers

What is the main function of Antithrombin III?

<p>Inhibition of the activity of thrombin and other coagulation factors (B)</p> Signup and view all the answers

Which activity of endothelial cells contributes to a fibrinolytic effect?

<p>Production of tissue plasminogen activator (B)</p> Signup and view all the answers

What effect does heparin have on thrombin function?

<p>Blocks thrombin function by forming a complex with Antithrombin III (B)</p> Signup and view all the answers

Why would administering heparin be ineffective if a thrombus is already formed in a patient?

<p>It would be useless to stop the activity as the thrombus is already formed (B)</p> Signup and view all the answers

Which is the primary function of platelets?

<p>Performing hemostasis by forming a primary hemostatic plug (A)</p> Signup and view all the answers

Which molecules are released from platelet granules during hemostasis?

<p>Fibrinogen, fibronectin, and coagulation factors (C)</p> Signup and view all the answers

Which molecule mediates the adhesion and aggregation of platelets by binding to $GpIIb-IIIa$?

<p>$vWF$ (C)</p> Signup and view all the answers

What is the role of integrins in platelet adhesion and aggregation?

<p>Crucial role in platelet adhesion and aggregation (A)</p> Signup and view all the answers

What happens when there is a deficiency in $vWF$ or integrins?

<p>Result in thrombosis or bleeding (C)</p> Signup and view all the answers

$GpIIb-IIIa$ binds to which molecule during platelet adhesion?

<p>Fibrinogen (D)</p> Signup and view all the answers

Which cells produce vWF and release it when the endothelium is damaged?

<p>Endothelial cells (D)</p> Signup and view all the answers

What is the initial step in the body's response to a ruptured vessel wall?

<p>Vasoconstriction (C)</p> Signup and view all the answers

What is the main function of platelets during hemostasis?

<p>Forming a primary hemostatic plug (C)</p> Signup and view all the answers

Which receptor is present on the membrane of platelets for adhesion and aggregation?

<p>Integrins (A)</p> Signup and view all the answers

Which molecule mediates the adhesion and aggregation of platelets by binding to $GpIb$?

<p>vWF (C)</p> Signup and view all the answers

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Study Notes

  • When a vessel wall is ruptured, the body initiates a hemostatic process to stop the bleeding.
  • The first step is vasoconstriction, which is a reflex response causing the vessels to constrict and reduce blood loss.
  • Next is primary hemostasis, where platelets adhere to the sub-endothelium and form a primary hemostatic plug.
  • Platelets are anucleated cells with a short life-span, their main function is to perform hemostasis.
  • Platelets contain granules (alpha and delta) that release important molecules for hemostasis, such as fibrinogen, fibronectin, and coagulation factors.
  • Platelets have receptors on their membrane, such as selectins, GPCRs, and integrins, for adhesion and aggregation.
  • Integrins, such as glycoprotein IIb/IIIa and glycoprotein Ib (GpIb), play a crucial role in platelet adhesion and aggregation.
  • vWF, a multimeric glycoprotein, mediates the adhesion and aggregation of platelets by binding to GpIIb-IIIa.
  • Endothelial cells produce vWF and release it when the endothelium is damaged.
  • During platelet adhesion, vWF binds to GpIb on platelets, then GpIIb-IIIa binds to fibrinogen, causing platelet aggregation.
  • A deficiency in vWF or integrins can result in thrombosis or bleeding, as platelets are not correctly bound to the sub-endothelium or to each other.

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