Platelet Plug & Coagulation Cascade Flashcards
When a blood vessel is damaged, what is its first response?
To vasoconstrict (due to neural control)
What initiates a platelet plug and coagulation cascade?
Endothelial damage
What is released by healthy endothelium & what does it do?
Nitric oxide (NO) and prostacyclin Vasodilates (keeps blood vessels open)
When a blood vessel/endothelium is damaged what is released and what does it do?
Endothelin-1 is released (by endothelial cells) and is used to vasoconstrict
What does vasoconstriction do?
Temporarity slows the flow of blood in the affected area
What also happens with the blood vessel?
This construction presses opposed endothelial surfaces of the vessel together and this contact induces a stickiness capable of keeping them glued together
What only occurs in the smaller vessels of the microcirculation?
Permanent closure of the vessel by constriction and contact stickiness
What are the two processes that stop bleeding?
Formation of a platelet plug and blood coagulation
What is found below endothelium and what happens to it when a vessel is injured?
There is collagen fibres
Injured vessels means endothelium is disrupted and exposes collagen fibres
What binds to exposed collagen?
Von willebrand factor (VWF) (factor 8) binds to exposed collagen at injured endothelium using glycoprotein 1B (GP1B) receptor
What happens after VWF binds to collagen?
Platelet adhesion - platelets bind to VWF on collagen via a GPIIa/IIIb receptor
What happens after platelets bind to VWF?
Binding triggers activation
Platelets are activated
What happens when platelets are activated?
Inactive: smooth & discoid
Active: spiculated (spiky) & pseudopoid
Exocytosis (release) of alpha/electron granules, amplified positive feedback, platelet aggregation
Forms a primary platelet plug
What happens after the platelet plug?
A coagulation cascade
What does the coagulation cascade form?
forms a mesh of fibrin over the primary platelet plug to make it more stable/add reinforcement
Forms secondary platelet plug
What are the 3 Pathways of the Coagulation cascade?
Intrinsic
Extrinsic
common
What are the 3 Pathways of the Coagulation cascade?
Intrinsic
Extrinsic
common
Describe the intrinsic pathway and its path
Uncommon
trauma inside blood vessels (internal damage)
12, 11, 9, 8, 10
Describe the extrinsic pathway and its path
Common
Extravascular trauma
Tissue factor 3 from damaged tissues activates 7
3, 7, 10
Describe the common pathway and its path
10 at the centre activates 2 (with help of 5) Factor 2: prothrombin ---> thrombin 2 activates 1 Factor 1: fibrinogen ---> fibrin
10, 5, 2, 1
What is the Fibrinolytic system?
A fibrin clot is not designed to last forever, it is a temporary fix until permanent repair of vessel occurs
What happens when vessel is fixed?
The secondary platelet plug is hydrolysed
What happens in the hydrolysis of the 2* platelet plug?
Tissue plasminogen activators convert plasminogen —> plasmin (fibrin eater)
Plasmin eats fibrin; fibrin —> fibrinogen (inactive)
Where are all clotting factors except one produced and which one?
All clotting factors except Von Willebrand Factor are produced in the liver
The liver is the site of production for?
Many of the plasma clotting factors
What does the liver produce and what is it essential for?
Bile salts
absorption of the lipid soluble substance, vitamin K
Why does the liver require vitamin K?
To produce prothrombin & several other clotting factors
Which factors are vitamin K dependent?
10, 9, 7, 2
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