Textbook Question
___ and ____ affect almost every aspect of the clotting process.
(a) Calcium, vitamin K
(b) Calcium, vitamin B12
(c) Sodium, vitamin K
(d) Sodium, vitamin B12
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17. The Blood
Platelets: Hemostasis
Problem 18
Textbook Question
What contribution from the intrinsic and the extrinsic pathways is necessary for the common pathway to begin?
Verified step by step guidance1
Understand the intrinsic and extrinsic pathways: The intrinsic pathway is activated by damage inside the blood vessel, while the extrinsic pathway is triggered by external trauma that exposes tissue factor (TF). Both pathways lead to the activation of the common pathway.
Identify the key components of the intrinsic pathway: The intrinsic pathway involves clotting factors such as Factor XII, Factor XI, Factor IX, and Factor VIII. These factors work sequentially to activate Factor X, which is necessary for the common pathway.
Identify the key components of the extrinsic pathway: The extrinsic pathway primarily involves tissue factor (TF) and Factor VII. When TF binds to Factor VII, it forms a complex that activates Factor X, which is also necessary for the common pathway.
Recognize the convergence point: Both the intrinsic and extrinsic pathways converge at the activation of Factor X. This is the critical step that initiates the common pathway, leading to the formation of thrombin and ultimately fibrin for clot stabilization.
Understand the role of Factor X in the common pathway: Once activated (Factor Xa), Factor X combines with Factor V, calcium ions, and phospholipids to convert prothrombin into thrombin, which is essential for the final steps of clot formation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Intrinsic Pathway
The intrinsic pathway of coagulation is initiated by damage to the blood vessel and involves a series of complex interactions among clotting factors that are already present in the bloodstream. This pathway is crucial for amplifying the coagulation response and leads to the activation of Factor X, which is essential for the common pathway of blood coagulation.
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Extrinsic Pathway
The extrinsic pathway is triggered by external trauma to a blood vessel, leading to the release of tissue factor (TF) from damaged tissues. This pathway is faster than the intrinsic pathway and directly activates Factor X when TF binds with Factor VII, providing a rapid response to vascular injury and facilitating the initiation of the common pathway.
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Common Pathway
The common pathway is the final stage of the coagulation cascade where both intrinsic and extrinsic pathways converge. It begins with the activation of Factor X, leading to the conversion of prothrombin to thrombin, which then converts fibrinogen to fibrin, forming a stable blood clot. Understanding this pathway is essential for comprehending how the body stops bleeding.
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