Chapter 17 - Part 2 Flashcards
Name the 3 steps for stoppage of bleeding
- vascular spasm
- platelet plug formation
- coagulation (blood clotting)
What is a vascular spasm?
vasoconstriction of damaged blood vessel
What are the 3 triggers of vascular spasm?
- direct injury
- chemicals released by endothelial cells and platelets
- pain reflexes
Describe the platelet plug formation at site of blood vessel injury…
- platelets contact exposed collagen fibers
- become sticky
- degranulate - release chemical messengers
- causes more platelets to stick and release their contents
- plug forms within one minute
What is a set of reactions in which blood is transformed from a liquid to a gel called?
coagulation
What does coagulation reinforce the platelet plug with?
fibrin threads
Coagulation is a multistep process…how many substances and enzymes does it require?
30
What are procoagulants?
inactive plasma clotting proteins
What do antiproagulants do?
prevent clotting
What are the 3 phases of coagulation?
- prothrombin activator is formed (intrinsic & extrinsic pathways)
- prothrombin is converted into trhombin
- thrombin catalyzes the joining of fibrinogen to form a fibrin mesh
Name the two pathways to prothrombin activator.
- intrinsic pathway
2. extrinsic pathway
What does the instrinsic pathway use? and what is it triggered by?
uses factors present within the blood
triggered by negatively charged surfaces
What does the extrinsic pathway bypass? and what is it triggered by?
bypasses several steps of intrinsic pathway, so is faster
triggered by exposure to tissue factor or factor III
What does factor X complexes involve in order to form prothrombin activator?
Ca2
PF3
factor V
What is the result of phase 1 in hemostasis?
prothrombin activator is formed
What is the result of phase 2 in hemostasis?
prothrombin activator catalyzes the transformation from prothrombin to thrombin
What is the result of phase 3 in hemostasis?
blood clot forms
Describe the pathway of phase 3 that results in blood clot.
thrombin ->
fibrinogen -> fibrin ->
forms a mesh; traps blood cells ->
blood clot
What speeds up the healing process?
clot retraction and repair of tissue
Describe the 5 steps of clot retraction and repair of tissue.
- actin and myosin in platelets contract within 30-60 minutes
- platelets pull on the fibrin strands, squeezing serum from the clot
- edges of wound pull together
- PGDF stimulates rebuilding of vessel wall
- VEGF stimulates regrowth of endothelium lining the vessel
What is the breakdown of the scab called?
fibrinolysis
How long does it take to happen after clotting?
within 2 days
What is plasminogen in the clot coverted to?
- plasmin by tissue plasminogen activator (tpa), factor XII and thrombin
What is plasmin?
fibrin-digesting enzyme
What does plasmin do?
breaks fibrin down to fragments and eventually to amino acids