Haemostasis
Prevents blood loss after damage to a vessel.
There are 4 stages for coagulation.
Vasoconstriction
Smooth muscle contracts/vascular spasm.
Vessel narrows.
Prevents blood loss.
Less blood flows to the area.
Platelets also secrete epinephrine and serotonin which also increases vasoconstriction.
Temporary Platelet plug
Platelets circulate the bloodstream.
When activated they stick together.
Platelets also secrete chemicals that attract other cells, in the clotting process, to the site of
injury.
Von Willebrand Factor (vWf) is secreted by the platelets and subendothelial tissue (when
exposed due to damage).
When damaged the collagen fibres on the subendothelial tissue binds to vWf.
, This anchors the platelets in place.
And causes platelets to secrete more of these chemicals to start the coagulation process.
Positive feedback loop.
ADH= released by platelets to cause them to adhere to each other and show the change in
the platelets in the diagram above.
More is secreted every time platelets adhere=positive feedback
ADH also stimulates thromboxane A2 production which also has platelet aggregation
properties.
Platelet plug is limited to the area of the damaged vessel to prevent unnecessary blood clots.
Blood clotting
A clotting factor cascade.
To form a fibrin clot.
When activated they form peptide bonds.
Intrinsic pathway: 12 activates 11 activates 9 activates 10.
Extrinsic: using calcium, 7 is activated to activate 10.
Thrombin converts fibrinogen to fibrin monomers.
These monomers form fibrin polymers
Which forms a mesh to trap erythrocytes.
Clot Retraction
Plasmin=dissolves the clot
Protein derived from plasminogen.
Breaks down fibrin.
Plasminogen activators are released by different cells to start this process.
Stops blockages for too long.
Haemophilia
Insufficiency in the intrinsic pathway
Due to a reduction of one of the factors
A: loss of factor 8
B: loss of factor 9
Vitamin K deficiency
Certain factors that are used in coagulation are not carboxylated.
This can lead to reduced blood clotting.
Naturally occurring in plants and in the gut
Essential in the formation of clotting factors
Vitamin K activates gamma-glutamyl carboxylate which adds a carboxyl group to allow
calcium ions to bind to the clotting factors to activate them.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller rosiemalley. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.87. You're not tied to anything after your purchase.