Haemostasis Quiz (BMS Learning Outcomes)

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Questions and Answers

What initiates the intrinsic pathway of coagulation in haemostasis?

  • Contact with collagen fibres (correct)
  • Platelet adherence to collagen
  • Release of tissue factor
  • Formation of a platelet plug

During primary haemostasis, what role do platelets play in the formation of a platelet plug?

  • They stabilize the clot through the release of thrombin.
  • They convert fibrinogen to fibrin.
  • They release serotonin and thromboxanes to constrict blood vessels.
  • They attract additional platelets through the release of ADP. (correct)

Which factor is directly activated by tissue factor in the extrinsic pathway?

  • Factor XII
  • Factor II
  • Factor X
  • Factor VII (correct)

What is the function of von Willebrand factor in primary haemostasis?

<p>Stabilizes the platelet plug (D)</p> Signup and view all the answers

What occurs during secondary haemostasis?

<p>Stabilization of the platelet plug with fibrin (A)</p> Signup and view all the answers

Which factor is involved in the initiation of the intrinsic pathway?

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

What is the primary purpose of vasoconstriction during primary haemostasis?

<p>To stop bleeding by reducing blood loss (C)</p> Signup and view all the answers

Which component is necessary for the conversion of soluble fibrinogen to fibrin?

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

What additional substance besides ADP can platelets release to assist in the aggregation of other platelets?

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

What is the first step that occurs when a blood vessel is damaged?

<p>Vasoconstriction of the vessel (D)</p> Signup and view all the answers

What substance is converted to thrombin during the common coagulation pathway?

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

Which vitamin is essential for the formation of clotting factors in the liver?

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

What is the primary role of thrombin in the coagulation process?

<p>To convert fibrinogen to fibrin (C)</p> Signup and view all the answers

What process pulls the edges of the damaged vessel together, reducing blood loss?

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

Which of the following conditions can prolong bleeding time?

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

What is th primary initial event in the process of thrombosis?

<p>Vascular endothelial damage (C)</p> Signup and view all the answers

What is the time range for a normal bleeding time, indicating primary hemostasis?

<p>2-7 minutes (A)</p> Signup and view all the answers

Which of these factors plays a role in clot breakdown?

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

Which factor is primarily responsible for stabilizing clots?

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

What occurs during clot retraction within 24 hours post-injury?

<p>Clot decreases by about 90% (B)</p> Signup and view all the answers

Flashcards

Haemostasis

The process by which bleeding stops when a blood vessel is damaged.

Primary Haemostasis: Vasoconstriction

The initial stage of haemostasis where blood vessels constrict to reduce blood flow.

Platelets

Small, cell-like fragments in blood that stick to the damaged vessel wall and release chemicals to initiate clotting.

Serotonin (5-HT)

A chemical released by platelets that causes smooth muscle in blood vessels to contract, narrowing the vessel.

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Platelet Plug

A temporary plug formed at the site of injury by the clumping of platelets.

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Secondary Haemostasis: Coagulation

A complex process that converts fibrinogen into fibrin, forming a stable mesh that reinforces the platelet plug.

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Fibrinogen

A protein in plasma that is converted into fibrin during coagulation.

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Clotting Cascade

A set of sequential reactions involving proteins called clotting factors, leading to the formation of fibrin.

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Extrinsic Pathway

The main pathway of the clotting cascade, triggered by tissue factor released from damaged cells.

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Intrinsic Pathway

The pathway of the clotting cascade triggered by blood contacting collagen fibres in the damaged vessel wall.

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What is haemostasis?

A complex process involving blood vessel constriction, platelet activation, and coagulation factors that stops bleeding.

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What is the common pathway in haemostasis?

The final stage of haemostasis where insoluble fibrin strands form a mesh, trapping blood cells and platelets, creating a stable clot.

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What are coagulation factors?

A series of enzymatic reactions involving coagulation factors that ultimately leads to the formation of thrombin, a crucial enzyme in clot formation.

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What is the role of Vitamin K in haemostasis?

Vitamin K is essential for liver synthesis of several coagulation factors, making it crucial for proper blood clotting.

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What is clot retraction?

A process that occurs after clot formation, where the clot contracts, becoming smaller and tighter, pulling together the edges of a damaged vessel and reducing blood loss.

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What is fibrinolysis?

This process involves the breakdown of the fibrin clot by the enzyme plasmin, restoring blood flow to the damaged area.

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What is thrombosis?

A condition where blood clots form abnormally in blood vessels, potentially obstructing blood flow and causing various health problems.

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What is bleeding time?

The primary haemostatic mechanism involving blood vessel constriction and platelet plug formation, typically taking 2-7 minutes.

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What is the expected bleeding time after a dental procedure?

It refers to the time it takes for bleeding to stop naturally after a dental procedure, usually within 4-10 minutes.

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What is the relevance of haemostasis to the dental hygienist/therapist?

Dental hygienists and therapists should understand haemostasis to manage bleeding during procedures, identify potential bleeding risks, and advise patients appropriately.

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Study Notes

Haemostasis and Clot Formation

  • Haemostasis is the process that stops bleeding after damage to blood vessels. It involves several overlapping steps.
  • Primary Haemostasis:
    • Vasoconstriction: Damaged blood vessels constrict to immediately reduce blood flow. Platelets adhere to the damaged vessel wall and release substances like serotonin and thromboxanes which further constrict vessels.
    • Platelet Plug: Platelets clump together at the site of damage, forming a plug. Von Willebrand factor stabilizes the plug. Platelets release ADP which attracts more platelets.
  • Secondary Haemostasis (Coagulation):
    • This process stabilizes the platelet plug.
    • Clotting Cascade: A complex series of reactions that lead to the formation of fibrin, an insoluble protein that forms a mesh.
    • Extrinsic Pathway: Triggered by tissue factor (released by damaged endothelial cells), activating factors VII, X, and eventually the common pathway.
    • Intrinsic Pathway: Triggered by exposed collagen in the damaged vessel wall, involving activation of factor XII, ultimately leading to the common pathway.
    • Common Pathway: Prothrombin is converted to thrombin. Thrombin converts fibrinogen to fibrin forming the mesh. Factor XIII strengthens the fibrin mesh.
  • Coagulation Factors:
    • Most are synthesized by the liver.
    • Vitamin K is essential for the liver's production of some clotting factors.
  • Clot Retraction:
    • Activated platelets contract, pulling the fibrin threads together, shrinking the clot, and expelling serum.
  • Clot Breakdown (Fibrinolysis):
    • Plasminogen, trapped in the clot, converts to plasmin that breaks down fibrin. TAFI is a fibrinolysis inhibitor, stabilizing the clot
  • Relevance to Dental Professionals:
    • Dental procedures can cause haemorrhage.
    • Bleeding should naturally stop within 4-10 minutes. Prolonged bleeding from dental procedures could indicate problems with clotting, necessitating additional assessment and management.

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