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Questions and Answers
What are the symptoms associated with severe blood loss exceeding 20%?
What are the symptoms associated with severe blood loss exceeding 20%?
Which of the following best describes the process of primary haemostasis?
Which of the following best describes the process of primary haemostasis?
What substance is released by platelets to enhance the formation of a platelet plug?
What substance is released by platelets to enhance the formation of a platelet plug?
Which condition can lead to prolonged bleeding time?
Which condition can lead to prolonged bleeding time?
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What is the primary role of serotonin released by platelets during primary haemostasis?
What is the primary role of serotonin released by platelets during primary haemostasis?
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Which of the following is NOT a symptom of severe blood loss?
Which of the following is NOT a symptom of severe blood loss?
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What is the time frame for primary haemostasis to occur after an injury?
What is the time frame for primary haemostasis to occur after an injury?
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Which component stabilizes the platelet plug during primary haemostasis?
Which component stabilizes the platelet plug during primary haemostasis?
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What is the primary process of haemostasis?
What is the primary process of haemostasis?
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What happens if there is rapid blood loss from the body?
What happens if there is rapid blood loss from the body?
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Which of the following describes the significance of clotting factors in the clotting cascade?
Which of the following describes the significance of clotting factors in the clotting cascade?
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Which of the following is a consequence of moderate blood loss?
Which of the following is a consequence of moderate blood loss?
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What role does haemostasis play in relationship to oral health?
What role does haemostasis play in relationship to oral health?
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Why is it important for the body to stop blood loss quickly when injured?
Why is it important for the body to stop blood loss quickly when injured?
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Which statement accurately describes the body's homeostatic mechanisms?
Which statement accurately describes the body's homeostatic mechanisms?
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What is a protective mechanism of blood apart from stopping bleeding?
What is a protective mechanism of blood apart from stopping bleeding?
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What is the primary role of fibrin in the clotting process?
What is the primary role of fibrin in the clotting process?
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Which factor is activated by tissue factor in the extrinsic pathway?
Which factor is activated by tissue factor in the extrinsic pathway?
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What does the common pathway of the clotting cascade ultimately lead to?
What does the common pathway of the clotting cascade ultimately lead to?
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How is the intrinsic pathway of the clotting cascade characterized?
How is the intrinsic pathway of the clotting cascade characterized?
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What substance is measured by Prothrombin Time (PT)?
What substance is measured by Prothrombin Time (PT)?
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Which factor is responsible for converting factor X into factor Xa?
Which factor is responsible for converting factor X into factor Xa?
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What does the number of clotting factors represent?
What does the number of clotting factors represent?
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Which statement best describes the function of the extrinsic pathway?
Which statement best describes the function of the extrinsic pathway?
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What initiates the intrinsic pathway of coagulation?
What initiates the intrinsic pathway of coagulation?
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Which coagulation factor is activated first in the intrinsic pathway?
Which coagulation factor is activated first in the intrinsic pathway?
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What is the normal range for Activated Partial Thromboplastin Time (aPTT)?
What is the normal range for Activated Partial Thromboplastin Time (aPTT)?
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Which factor is crucial for the synthesis of clotting factors in the liver?
Which factor is crucial for the synthesis of clotting factors in the liver?
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Which inherited disorder leads to a deficiency of factor IX?
Which inherited disorder leads to a deficiency of factor IX?
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What role does thrombin play in the coagulation cascade?
What role does thrombin play in the coagulation cascade?
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What is the primary effect of anticoagulants like Warfarin and Heparin?
What is the primary effect of anticoagulants like Warfarin and Heparin?
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Which of the following conditions is NOT indicated for the use of anticoagulants?
Which of the following conditions is NOT indicated for the use of anticoagulants?
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What is the primary purpose of clot retraction within 24 hours after clot formation?
What is the primary purpose of clot retraction within 24 hours after clot formation?
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What role does plasmin play in the clot breakdown process?
What role does plasmin play in the clot breakdown process?
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Which of the following conditions is associated with depressed fibrinolysis?
Which of the following conditions is associated with depressed fibrinolysis?
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What causes thrombosis primarily to occur?
What causes thrombosis primarily to occur?
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Which method is least commonly used to control haemorrhage in dentistry?
Which method is least commonly used to control haemorrhage in dentistry?
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During which condition is fibrinolysis enhanced?
During which condition is fibrinolysis enhanced?
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What is the effect of thrombin-activated fibrinolysis inhibitor (TAFI)?
What is the effect of thrombin-activated fibrinolysis inhibitor (TAFI)?
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What is the usual time frame for bleeding to stop naturally after dental procedures?
What is the usual time frame for bleeding to stop naturally after dental procedures?
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Study Notes
Haemostasis
- The process of stopping bleeding.
- When a blood vessel is damaged, a series of processes occur to stop the bleeding.
Why is Haemostasis Important?
- Blood is an important connective tissue.
- Keeps all organs nourished.
- Injury can lead to blood loss, making it important to stop bleeding as quickly as possible.
Consequences of Blood Loss
- Minor loss: Small wound, usually self-healing.
- Moderate loss: Larger wound, may need treatment, possible symptoms include headache, fatigue, nausea, sweating, dizziness. Younger and elderly people are at greater risk.
- Severe loss: More than 20% blood loss can lead to shock, clammy skin, rapid shallow breathing, rapid heart rate, little to no urine output, confusion, weakness, weak pulse, blue lips and fingernails, light-headedness, loss of consciousness, and death. Can lead to anemia and oral impacts.
Stages of Haemostasis
- Divided into two primary parts:
- Primary haemostasis: Initial bleeding stopped by vasoconstriction and platelet plug formation.
- Secondary haemostasis: Platelet plug is stabilized by forming insoluble fibrin strands to form a mesh.
Primary Haemostasis
-
Vasoconstriction: Blood vessels constrict to minimize blood loss.
- Platelets adhere to the damaged vessel wall.
- Platelets release serotonin (5-HT) and thromboxanes, causing the smooth muscle in the vessel wall to contract and constrict the blood vessel.
- Endothelins, which are released by damaged vessels, also act as vasoconstrictors.
-
Platelet plug formation: Platelets clump together at the site of injury to form a plug.
- Platelets adhere to exposed collagen fibers.
- The glycoprotein von Willebrand factor stabilizes the platelet plug.
- Platelets release chemicals like adenosine diphosphate (ADP) that attract more platelets to the site.
Bleeding time
- Reflects the time taken for primary haemostasis (vasoconstriction and platelet plug formation) to occur.
- Normal range: 2-7 minutes.
- Prolonged bleeding time can be caused by conditions such as thrombocytopenia, severe anemia, collagen disorders such as Ehlers Danlos syndrome, von Willebrand's disease, and anti-platelet drugs like aspirin and clopidogrel.
Secondary Haemostasis
- Coagulation: A complex process that results in the formation of a fibrin mesh that stabilizes the platelet plug.
- Fibrin is formed from soluble fibrinogen through the clotting cascade.
- The clotting cascade is a series of interconnected reactions involving several clotting factors.
Clotting Factors
- Number of factors reflects the order in which they were discovered, not necessarily their order in the clotting cascade.
- Most clotting factors are synthesized in the liver.
- Factor VII is created by vascular endothelium.
- Vitamin K is essential for the formation of clotting factors in the liver.
- Liver pathology can affect clotting factor production.
Three Pathways of Coagulation
-
Extrinsic Pathway (Tissue factor pathway): Triggered by the release of tissue factor (factor III) from damaged endothelial cells.
- Tissue factor converts factor VII to factor VIIa.
- Factor VIIa activates factor X to factor Xa.
- Measured by prothrombin time (PT), normal value: 11-16 seconds.
-
Intrinsic pathway (contact pathway): Triggered by blood coming into contact with collagen fibers in the broken wall of a blood vessel.
- "Intrinsic" because it is initiated by a factor inside the blood vessel.
- Starts with the activation of factor XII, which becomes factor XIIa after exposure to endothelial collagen.
- Ends with the common pathway.
- Measured by activated partial thromboplastin time (aPTT), normal value: 23-35 seconds.
-
Common pathway: Connects the intrinsic and extrinsic pathways.
- Factor Xa converts prothrombin to thrombin.
- Thrombin converts soluble fibrinogen to insoluble fibrin strands.
- Factor XIII strengthens the fibrin mesh.
Effects of Anticoagulants on Clotting Cascade
- Anticoagulants are drugs that help prevent blood from clotting.
- Different anticoagulants block various points in the clotting cascade.
- Examples: warfarin, heparin, and rivaroxaban.
- Indications: atrial fibrillation, deep vein thrombosis, stroke.
- Increased bleeding risk is a potential side effect of anticoagulants.
Clot Retraction
- Contraction of up to 90% of the initial clot volume within 24 hours.
- Actin and myosin proteins within activated platelets pull the clot tight.
- Fibrin threads are drawn closer together.
- Serum is expelled.
- Clot shrinkage pulls the edges of the damaged vessel together, reducing blood loss.
Clot Breakdown - Fibrinolysis
- Plasminogen is converted into plasmin, an enzyme that breaks down fibrin.
- Thrombin-activated fibrinolysis inhibitor (TAFI) stabilizes clots.
- Fibrinolysis is enhanced by disseminated intravascular coagulation, metastatic prostate cancer, sepsis, trauma, and severe burns.
- Fibrinolysis is depressed by alcoholic liver disease, antiphospholipid syndrome, hypothyroidism, chronic renal disease, and pregnancy.
Thrombosis
- Blood clots from a combination of over-activity of coagulation and under-activity of fibrinolysis.
- Commonly starts at an area of vascular endothelial damage where platelets adhere.
Dental Relevance
- Dental procedures can cause bleeding.
- Bleeding should stop naturally after 4-10 minutes depending on the wound.
- Prolonged bleeding can be caused by a variety of factors.
Haemorrhage in Dentistry
- Controlled by: pressure, sutures, packing with hemostatic agents such as Surgicel.
- Less commonly: electrosurgery unit, lasers.
Summary
- The process of haemostasis and clot formation was described, highlighting the importance of primary and secondary haemostasis.
- The clotting cascade, including the intrinsic, extrinsic, and common pathways, was explained, along with the role of clotting factors and their significance.
- Clot retraction and fibrinolysis were briefly discussed, emphasizing their respective roles in clot stabilization and breakdown.
- The relevance of haemostasis for dental hygienists and therapists was addressed, emphasizing the need to understand bleeding control and management in dental procedures.
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Description
Explore the crucial process of haemostasis, which is vital for stopping bleeding when a blood vessel is damaged. This quiz covers the stages of haemostasis, the importance of blood, and the consequences of blood loss, including symptoms and treatment. Test your knowledge on this essential topic in human physiology.
