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Questions and Answers
What are the risks associated with blood transfusions?
What are the risks associated with blood transfusions?
How does a father with hemophilia affect his daughters?
How does a father with hemophilia affect his daughters?
Which in vitro anticoagulant is used to precipitate calcium?
Which in vitro anticoagulant is used to precipitate calcium?
What percentage of hemophilia cases may arise from new mutations without a prior family history?
What percentage of hemophilia cases may arise from new mutations without a prior family history?
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What is a potential complication of blood transfusion related to compatibility?
What is a potential complication of blood transfusion related to compatibility?
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Which of the following diseases is NOT an indication for blood transfusion?
Which of the following diseases is NOT an indication for blood transfusion?
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What is one characteristic of heparin as an anticoagulant?
What is one characteristic of heparin as an anticoagulant?
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What is the expected chance of a son of a haemophiliac father having haemophilia?
What is the expected chance of a son of a haemophiliac father having haemophilia?
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What is the primary purpose of hemostasis?
What is the primary purpose of hemostasis?
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Which process follows platelet activation in the mechanism of platelet plug formation?
Which process follows platelet activation in the mechanism of platelet plug formation?
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What initiates the intrinsic pathway of blood coagulation?
What initiates the intrinsic pathway of blood coagulation?
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Which of the following is NOT a cause of thrombocytopenia?
Which of the following is NOT a cause of thrombocytopenia?
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Haemophilia A is primarily inherited through which of the following mechanisms?
Haemophilia A is primarily inherited through which of the following mechanisms?
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What is the normal range for platelet count in individuals?
What is the normal range for platelet count in individuals?
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Which step is considered the ultimate step in the clot formation process?
Which step is considered the ultimate step in the clot formation process?
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What is NOT a characteristic of spontaneous skin purpura and hemorrhage in thrombocytopenia?
What is NOT a characteristic of spontaneous skin purpura and hemorrhage in thrombocytopenia?
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Study Notes
Haemostasis & Bleeding Disorders
- Haemostasis is the prevention of blood loss or stoppage of bleeding.
- Haemostasis is a process of forming clots in the walls of damaged blood vessels to prevent blood loss, maintaining blood in a fluid state within the vascular system.
Major Components of Haemostasis
- Vascular injury initiates haemostasis.
- Collagen and tissue factor are involved.
- Platelet activation leads to a platelet plug (primary haemostasis).
- Coagulation cascade (secondary haemostasis) results in blood clot formation, involving thrombin, fibrinogen, and fibrin.
- Antithrombotic mechanisms control clot formation.
- Fibrinolysis and clot degradation are part of the process.
Platelets (Thrombocytes)
- Platelets are small, non-nucleated oval cells.
- They are formed in bone marrow.
- Normal platelet count is 150,000 - 450,000 cells/cmm.
- Platelets have a lifespan of 8 days.
- Platelets are activated when they encounter damaged blood vessel walls or abnormal surfaces.
Platelet Plug Formation
- Platelet adherence (platelets attach to damaged vessel wall).
- Platelet activation (platelets become activated and release substances).
- Platelet aggregation (activated platelets clump together forming a plug).
Haemostasis Stages
- Vascular spasm: Narrowing of the blood vessel.
- Platelet plug formation: Platelets aggregate at injury site.
- Blood clot formation (coagulation): A fibrin mesh forms, trapping blood cells. Clot retraction strengthens the clot.
Blood Clot (Coagulation) Formation
- If there is a large hole, a blood clot is needed.
- The clot begins to develop few seconds after the injury.
- Coagulation pathways: Intrinsic and extrinsic pathways lead to the common pathway, culminating in thrombin converting fibrinogen to fibrin.
Blood Coagulation (clotting)
- Three main steps: formation of prothrombin activators, conversion of prothrombin into thrombin, conversion of fibrinogen into fibrin threads.
Intrinsic vs Extrinsic Pathways
- Intrinsic pathway: Activated when blood contacts a rough surface.
- Extrinsic pathway: Activated when blood comes into contact with material from damaged tissues.
- Both pathways converge at a shared pathway, leading to clot formation.
Classification of Bleeding Disorders
- Blood vessel defects: Hereditary (e.g., hereditary hemorrhagic telangiectasia), Connective tissue diseases (e.g., Marfan's syndrome, Ehlers-Danlos syndrome), Acquired (e.g., severe infections, drugs).
- Platelet defects: Thrombocytopenia (decreased platelet production or destruction), Decreased platelet function (e.g., Bernard-Soulier syndrome).
- Coagulation defects: Hereditary (e.g., hemophilia A, B, Von Willebrand disease), Acquired (e.g., anticoagulants, liver disease, DIC).
Thrombocytopenia
- Thrombocytopenia is caused by a decrease of circulating platelets.
- It is characterised by spontaneous skin purpura & hemorrhage & prolonged bleeding after trauma.
Causes of Thrombocytopenia
- Failure of platelet production (e.g., bone marrow failure).
- Increased platelet consumption (e.g., immune-mediated thrombocytopenia, disseminated intravascular coagulation).
Haemophilia
- A group of inherited blood disorders with a lifelong defect in clotting.
- Caused by a deficiency or absence of functional coagulation factor VIII (Haemophilia A) or factor IX (Haemophilia B).
Haemophilia Inheritance
- X-linked recessive trait.
- Inherited through the X chromosome.
- Common in males.
- Females can be carriers.
Haemarthrosis
- Haemarthrosis describes bleeding into a joint. A characteristic symptom of severe haemophilia.
Blood Transfusion
- A common medical procedure.
- Stored in components such as packed red blood cells (PRBCs), individual factor concentrates and fresh frozen plasma (FFP), and platelet concentrates.
Indications for Blood Transfusion
- Loss of large amount of blood as in hemorrhage
- Severe anemia
- Severe leucopenia (decreased WBCs)
- Thrombocytopenic purpura (decreased platelets)
- Haemophilia.
Complications of Blood Transfusion
- Febrile reactions
- Transfusion-associated circulatory overload
- Allergic reaction
- Infections (e.g., hepatitis C)
- Human immunodeficiency virus infection.
- Fatal hemolysis (ABO incompatibility)
Anticoagulants
- In vitro anticoagulants: Used outside the body to prevent clotting (e.g., smooth siliconized containers, oxalate compounds, citrate compounds, heparin).
- In vivo anticoagulants: Used inside the body to prevent clotting (e.g., heparin, coumarin).
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Description
This quiz focuses on the mechanisms of haemostasis, highlighting the processes involved in stopping bleeding and forming clots. Learn about the major components, including the role of platelets and the coagulation cascade, crucial for maintaining vascular integrity.
