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Questions and Answers
What is the primary purpose of haemostasis?
What is the primary purpose of haemostasis?
The process of primary haemostasis involves the activation of coagulation factors.
The process of primary haemostasis involves the activation of coagulation factors.
False
Name the five major components of the haemostatic system.
Name the five major components of the haemostatic system.
Blood vessels, Platelets, Coagulation factors, Coagulation inhibitors, Fibrinolysis
Intact endothelial cells of the intima are considered _____ (e.g., they prevent thrombus formation).
Intact endothelial cells of the intima are considered _____ (e.g., they prevent thrombus formation).
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Match the types of haemostasis with their corresponding processes:
Match the types of haemostasis with their corresponding processes:
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Which of the following is NOT a component of the haemostatic system?
Which of the following is NOT a component of the haemostatic system?
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The mechanism of primary haemostasis includes the formation of a fibrin strand.
The mechanism of primary haemostasis includes the formation of a fibrin strand.
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What is the result of a platelet adhering to a vessel wall during primary haemostasis?
What is the result of a platelet adhering to a vessel wall during primary haemostasis?
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Haemostasis works to prevent _____ and ensure proper blood clotting.
Haemostasis works to prevent _____ and ensure proper blood clotting.
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What happens during secondary haemostasis?
What happens during secondary haemostasis?
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What is the role of Von Willebrand Factor (vWF) in hemostasis?
What is the role of Von Willebrand Factor (vWF) in hemostasis?
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Platelets are produced in the liver.
Platelets are produced in the liver.
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What is the normal platelet count range in x 10^9/L?
What is the normal platelet count range in x 10^9/L?
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Platelets spend about _____ days in circulation before being cleared in the spleen.
Platelets spend about _____ days in circulation before being cleared in the spleen.
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Match the following platelet granules with their contents:
Match the following platelet granules with their contents:
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What initiates the release of Von Willebrand Factor (vWF) from endothelial cells?
What initiates the release of Von Willebrand Factor (vWF) from endothelial cells?
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Thrombopoiesis occurs in the lungs.
Thrombopoiesis occurs in the lungs.
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What is synthesized by platelets when activated?
What is synthesized by platelets when activated?
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The diameter of platelets on a blood film is approximately _____ µm.
The diameter of platelets on a blood film is approximately _____ µm.
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Which component of blood vessels undergoes vasospasm during injury?
Which component of blood vessels undergoes vasospasm during injury?
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Study Notes
Haemostasis - Part I: Primary Haemostasis
- Haemostasis is the process of stopping bleeding.
- Primary Haemostasis is the initial step in haemostasis.
- The haemostatic system has 5 major components:
- Blood vessels
- Platelets
- Coagulation factors
- Coagulation inhibitors
- Fibrinolysis inhibitors
Aims and Objectives
- The aim is to outline the processes involved in normal haemostasis.
- Learning objectives include:
- Explaining the importance of effective haemostasis
- Describing major components of haemostatic mechanisms
- Describing mechanisms of primary haemostasis
What is Haemostasis?
- Haemostasis is the process of stopping bleeding or blood flow.
- It is a complex process involving several stages.
- The process is tightly regulated, too much (thrombosis) or too little (bleeding) is harmful.
Primary and Secondary Haemostasis
- Primary haemostasis is the initial phase and involves platelets adhering to the damaged site, forming a temporary plug.
- Secondary haemostasis is the subsequent phase and involves coagulation factors activating to produce a more stable fibrin clot.
Blood Vessels in Haemostasis
- Arteries and veins are composed of three layers: intima, media, and adventitia.
- Intact endothelium (inner lining) has anti-thrombotic properties.
- Damage to the endothelium exposes underlying prothrombotic substances like collagen.
Von Willebrand Factor (vWF)
- vWF is a multimeric glycoprotein.
- Stored in Weibel-Palade bodies in endothelial cells.
- Released into the blood.
- It is crucial for platelet adhesion to the subendothelium.
- It can be broken down by ADAMTS-13 for control.
- vWF is also stored in platelet alpha-granules.
Platelets
- Platelets are produced by megakaryocytes in the bone marrow.
- Normal platelet count is 150-400 x 109/L.
- Platelets circulate for 6-9 days before being removed by the spleen.
- Size: 2-3 µm, appear purple on blood smears.
- Activation is necessary for platelet function in haemostasis.
- Platelets contain different granules (alpha, dense, lysosomes) with various proteins, molecules, and enzymes, which are released upon activation (for example, serotonin, ADP, ATP, clotting factors).
Primary Haemostasis: Part I
- Injury to the Blood Vessel initiates vasoconstriction (narrowing of the blood vessel).
- Vasoconstriction slows/stops blood flow.
- vWF in the plasma binds to exposed collagen.
- Platelets at the edge of the circulation are captured and bind to GPIb.
Primary Haemostasis: Part II
- Platelet Rolling and Interactions are initial interactions between platelets and the injured site and vWF activation.
- Stable Adhesion of platelets to exposed collagen occurs.
- GPVI activation happens due to platelet adhesion by collagen.
- Activated Integrin α2β3 binds to fibrinogen (platelet-platelet interactions occur during aggregation).
- Shape change and irreversible shape change (lamellarpodia and filopodia)
- Aggregation forms a temporary platelet plug.
Primary Haemostasis—Summary
- Primary haemostasis forms an unstable temporary platelet plug for faster wound healing/repair.
- It requires strengthening by secondary coagulation mechanisms.
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Description
This quiz focuses on the initial step in the haemostatic process known as Primary Haemostasis. You will explore the components involved, including blood vessels, platelets, and coagulation factors. Understand the mechanisms that play a vital role in effectively stopping bleeding.
