Blood Coagulation (read notes too) Flashcards
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What is the main purpose of blood clotting?
The main purpose of blood clotting is to prevent excessive bleeding and protect the body from pathogens entering through a wound.
What triggers the initial response in blood clotting when a blood vessel is damaged?
The exposure of collagen triggers the initial response, attracting platelets to the site of injury.
What is haemostasis?
Haemostasis is the process that stops bleeding in response to blood vessel injury. It includes vasoconstriction, platelet plug formation, coagulation, and eventually clot breakdown.
What are platelets and where are they made?
Platelets are small cell fragments called thrombocytes, made from megakaryocytes in the bone marrow.
Describe the sequence of events in platelet plug formation.
Platelet plug formation begins with platelet adhesion to exposed collagen, followed by platelet activation, and ends with platelet aggregation to form a temporary plug.
How does fibrin strengthen a blood clot?
Fibrin forms a mesh from soluble fibrinogen proteins at the site of injury, trapping platelets and other blood components to create a strong, stable clot.
What is the difference between primary and secondary haemostasis?
Primary haemostasis involves platelet plug formation, while secondary haemostasis involves the coagulation cascade that leads to the conversion of fibrinogen to fibrin to stabilize the clot.
What happens during fibrinolysis?
During fibrinolysis, the clot is broken down after vessel repair, dissolving the fibrin mesh and restoring normal blood flow.
What glycoproteins are involved in platelet adhesion, and how do they interact with collagen?
GPIb-V-IX binds to von Willebrand factor (vWF) on collagen, while GPVI and GPIa/IIa bind directly to exposed collagen, leading to platelet activation.
What role does thrombin play in blood clotting?
Thrombin is a key enzyme in the coagulation cascade that converts fibrinogen to fibrin and also promotes further platelet activation and recruitment.
What is the significance of the coagulation factors being designated by Roman numerals?
The Roman numerals identify specific coagulation factors, with an added lowercase “a” indicating their active forms, such as Factor I (fibrinogen) and Factor II (prothrombin).
What is the difference between a thrombus and an embolus?
A thrombus is a stationary blood clot, while an embolus is a clot that has broken loose and travels through the bloodstream, potentially causing blockages.
Why don’t platelets and fibrin become sticky inside healthy blood vessels?
Platelets and fibrin only become sticky after being exposed to external signals at a wound site, preventing unwanted clotting in healthy vessels. Prostaglandins also help prevent spontaneous clotting.
What can happen if the balance between pro-coagulant and anticoagulant factors is disrupted?
A disruption in haemostatic balance can lead to conditions like thrombosis, where unnecessary clots form and restrict blood flow.
How does vasoconstriction contribute to haemostasis?
Vasoconstriction reduces blood flow at the site of injury, which helps to minimize blood loss and facilitates platelet plug formation.
What is the lifespan of a platelet, and how are they produced?
Platelets have a lifespan of 7–10 days and are produced in the bone marrow by megakaryocytes, which can generate over 1,000 platelets each.
What is the function of von Willebrand factor (vWF) in platelet plug formation?
vWF binds to exposed collagen at the site of injury and helps platelets adhere to the wound by interacting with the glycoprotein GPIb-V-IX.
What does the term ‘coagulation cascade’ refer to?
The coagulation cascade is a series of enzyme-activating reactions that lead to the conversion of fibrinogen into fibrin, ultimately forming a stable blood clot.
Which coagulation factors are especially important, and what are their roles?
Important coagulation factors include Factor I (fibrinogen), which forms fibrin; Factor II (prothrombin), which is converted to thrombin; and Factor III (tissue factor), which initiates the cascade. As well as factor X which connects the extrinsic and intrinsic pathway in the coagulation cascade to make thrombin
What is the role of fibrin in the formation of a scab?
Fibrin forms a mesh that traps platelets and other blood cells, creating a stable clot that eventually dries and forms a scab to protect the wound during healing.
