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?

Stabilizes the platelet plug Signup and view all the answers

What occurs during secondary haemostasis?

Stabilization of the platelet plug with fibrin Signup and view all the answers

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

Factor XII Signup and view all the answers

What is the primary purpose of vasoconstriction during primary haemostasis?

To stop bleeding by reducing blood loss Signup and view all the answers

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

Thrombin Signup and view all the answers

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

Thromboxanes Signup and view all the answers

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

Vasoconstriction of the vessel Signup and view all the answers

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

Prothrombin Signup and view all the answers

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

Vitamin K Signup and view all the answers

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

To convert fibrinogen to fibrin Signup and view all the answers

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

Clot retraction Signup and view all the answers

Which of the following conditions can prolong bleeding time?

Thrombocytopaenia Signup and view all the answers

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

Vascular endothelial damage Signup and view all the answers

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

2-7 minutes Signup and view all the answers

Which of these factors plays a role in clot breakdown?

Plasmin Signup and view all the answers

Which factor is primarily responsible for stabilizing clots?

Factor XIII Signup and view all the answers

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

Clot decreases by about 90% Signup and view all the answers

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.