Hemostasis and Blood Coagulation Flashcards
what are the functions of the coagulation system?
rapid formation of mechanically sound clot
prevent clot formation at noninjured sites
gradual replacement of clot with viable tissue
relate the following action from the coagulation system with the desired result:
rapid formation of mechanically sound clot
Stop bleeding quickly
relate the following action from the coagulation system with the desired result:
prevent clot formation at noninjured sites
prevent thrombosis
relate the following action from the coagulation system with the desired result:
gradual replacement of clot with viable tissue
wound healing
what are the 3 steps of Hemostasis?
step 1: vascular spasm
step 2: platelet plug formation
step 3: coagulation
describe step 1: vascular spasm of hemostasis?
1) Reflex contraction of smooth muscle in the wall of small blood vessels (alpha 1 receptors on smooth muscle)
2) Reaction to injury – spasm Reduces diameter and cuts flow almost instantly
describe step 2: platelet plug formation of hemostasis?
Smooth vessel walls do not attract platelets (Blood vessels & platelets both positively charged so repulsion occurs)
Rough surfaces cause platelet adhesion
Once attracted, they release serotonin (enhance the vascular spasm), also, ADP, Thromboxane A2 (NSAIDS for clotting issues)
Within one minute this step occurs : Platelet plug will stop very minor “leaks”
If a severe cut, we move to step 3
describe step 3: coagulation of hemostasis?
complex of 20 substances
what step of the hemostasis process is occurring when:
Platelets stick to exposed collagen underlying damaged endothelial cells in vessel wall?
step 1
what step of the hemostasis process is occurring when:
Release Thromboxane A2, Serotonin & ADP activating other platelets:
Serotonin& Thromboxane A2 are vasoconstrictors decreasing blood flow through the injured vessel.
ADP causes stickiness
step 2
what step of the hemostasis process is occurring when:
Activated platelets stick together and activate new platelets to form a mass called a platelet plug
Plug reinforced by fibrin threads formed
during clotting process
step 3
what are two components important in blood coagulation?
platelet plug and fibrin clot
what do platelets do?
Stick to damaged blood vessels
requires von Willebrand factor
Spread out to cover damaged area
Activate and release contents
partly blocked by aspirin
Aggregate
Cause blood vessel constriction
Cause retraction of clot to draw wound edges together
in terms of what platelets do, the fact that platelets stick to damaged blood vessels requires this kind of factor?
von Willebrand factor
in terms of what platelets do, activation and release of contents are partly blocked by?
aspirin
*what is unique about von Willebrand factor?
shaped as a globular protein in its inactive form and unfolds under shear stress as an extended chain to keep platelets in the area to cover affected area by releasing glycoprotein receptors:
GP IIb/IIIa: Binds fibrinogen, allows platelets to aggregate with each other
the platelets contain an ALPHA GRANULE that holds the vWF, calcium that helps with adhesion and smooth muscle contraction, and glycoprotein receptors(inside platelet) :
GP Ib/IXa: Binds von Willebrand Factor (vWF), allows platelets to adhere to subendothelial tissue
T/F, fibrin clot formation is a tightly controlled process?
T
what initiates fibrin clot formation?
tissue factor and this forms a hemostatic envelope if clot is not enough
Not normally found on endothelial cells lining blood vessels, or on circulating blood cells
what is significant about Hemostasis-step 3: Coagulation & Clot Stabilization?
it is a cascade of events for clot formation
once collagen is available, factor 12 is activated, it will activate 11, then 9, it sends an activator to activate factor 10 it is at this point that intrinsic and extrinsic pathways combine and the difference is what initiates each pathway:
intrinsic: collagen
extrinsic: tissue factor III
the extrinsic pathway is activated when tissue factor III is present which activates factor VII and this combines at level of factor 10
once both pathways meet at factor 10, it becomes a common pathway (at the same time the coagulation system is active at the site and proximal) and converts prothrombin to thrombin which changes fibrinogen to fibrin. Note that factor 13 is activated by thrombin to change fibrin into a mesh like cross linked fibrin (clot for wound)
what is significant about factor 8?
it combines factor 9 and 7 together so that 10 can become activated so that 10 can become activated
in fibrin clot formation, tissue damage exposes blood to _____?
tissue factor
in fibrin clot formation, the coagulation cascade: series of enzymatic reactions lead to ____ formation?
thrombin
in fibrin clot formation, what does thrombin convert fibrinogen into?
fibrin
after fibrin polymerizes, what does it become?
crosslinked
in fibrinolysis, degradation of fibrin clot is carried out by the enzyme called _____?
plasmin, which is necessary to remove to clot so wound healing can proceed
in fibrinolysis, these are from blood vessels and other cells convert plasminogen to plasmin to begin the process
plasminogen activators
how does thrombosis inactivation occur?
antithrombin III binds to a heparin like molecule and inactivates thrombin and factors 10a and 9a
in terms of thrombosis inactivation, what is the tissue factor pathway inhibitor?
small molecules that work on factors 7a and 10a
in terms of thrombosis inactivation, what is protein C in the coagulation cascade?
after thrombin is made by coagulation cascade, protein C is activated and lysis activated factors 5a and 8a
in terms of thrombosis inactivation, what is t-PA in the coagulation cascade
aids in the fibrinolytic cascade
in terms of clotting, how is Vitamin K needed?
for production of several clotting proteins
Fat-soluble vitamin present in many foods
Some made by bacteria in gut
Necessary for synthesis of several components of coagulation cascade (Factors II, VII, IX, and X)
Deficiency may lead to low levels of clotting factors, causing a bleeding tendency
Warfarin (Coumadin™): a drug that interferes with vitamin K action
used as an anticoagulant (prevent thrombosis)
Vitamin K is necessary for synthesis of several components of coagulation cascade, what are they?
Factors II, VII, IX, and X
a drug that interferes with vitamin K action
used as an anticoagulant (prevent thrombosis)
Warfarin (Coumadin)
vitamin K is necessary for the binding of these molecules in the production of thrombin?
enzyme, proenzyme, helper to phospholipid membrane
what do we mean when say the regulation of coagulation? what are the important molecules that are a part of this? what happens when there is a deficiency of these?
confines clot to injured area and helps prevent thrombosis; antithrombin, protein C, protein S
Deficiency of any of these proteins can increase risk of thrombosis causes clotting issues not being made at the proper rate
what is antithrombin?
inhibits thrombin and other enzymes
what is protein C?
degrades activated factors V and VIII
what is protein S?
cofactor for protein C
what are drugs that interfere with clotting?
aspirin- Often recommended for those over 50, reduces stickiness of platelets.
coumadin- Maintenance for those prone to clotting – and in atrial fibrillation
plavix– Newer – maintenance drug
heparin– Used in IV lines and blood collection
Typically suspend these before surgery
