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Factor released by platelets to cause vasoconstriction?
Four mechanisms to hemostasis?
- 1. vascular constriction
- 2. platelet plug
- 3. blood coagulation
- 4. growth of fibrous tissue
Contactile fibers contained in platelets
actin, myosin, thombosthenin
Ion stored by platelets?
Calcium, dence granual
Functions of platelet derived growth factor
causes vascular smooth muscle, vascular endothelial cells, and fibroblasts to grow and multiply
Molecule on platelet surface that activates clotting (generic)
Half life of platelets and method of distraction
8-12 days, tissue macrophages, mainly spleen
when platelets bind to the endothelium what causes the release of granolas?
three location of vWF
platelets, endothelium, circulation
Two secretions of platelets that activate more platelets?
ADP, thromboxan A2
Responsible for plugging thousands of vascular holes daily?
major functional unit of clot retraction?
Two outcomes of a blood clot?
- 1. can be invaded by fibroblasts and form connective tissue, promoted by PDGF, 1-2 weeks
- 2. dissolve
Three essential steps of blood coagulation?
- 1. formation of a complex of activated substances called prothrombin activator, rate limiting step in blood coagulation
- 2. The activator catalyzes prothrombin to thrombin in the presence of calcium
- 3. Thrombin convers fibrinogen to fibrin
Prothrombin activator is formed in result of?
- vascular damage
- damage to special substances in the blood
Name and function of GPIIb/IIIa?
prothrombin receptor, on the cell membrane of platelets already bound to damaged tissues
prothrombin and bradykinin
Does fibrinogen leak of of vessels?
- no, it is too large.
- During pathological conditions vascular permeability can increase enough to let it out
Reticulum of a blood clot?
Long fibrin chain attached to clot
Fibrin stabilizing factor, site of storage and function.
released by activated platelets and cross links fibrin monomers by covalent bonds
Origin of serum?
- after a clot is formed the platelets contract and squeeze out all the fluid, this fluid is serum.
- does not contain clotting factors
Failure of a clot to retract indicates?
low platelet level
Platelets release what that cause clot contraction?
ATP and calcium to activate actin/myosin and thrombosthenin
factors activated thrombin act on
2, 8, 9, 10,11, and 12
three initiating events of prothrombin activator formation
- 1. trauma to vascular wall
- 2. trauma to blood
- 3. contact of blood with collagen
Two pathways of prothrombin activator?
- Intrinsic- damage to blood
- Extrinsic-damage to vascular wall
Factor that activates prothrombin activator?
What is released form damaged blood vessels to initiate the extrinsic pathway?
tissue factor, tissue throboplastin
Two main proteins of prothrombin activator
- X and V and calcium
- factor X is the protease in this complex, V accelerates the action
- thrombin itself has posotive feedback on factor V
Initiation of the intrinsic pathway?
- blood trauma, release of factor XII (activated when it contacts collagen surface or glass)
- exposure of of blood to collagen
Cleavage of XI by XII needs?
HMW kininogen, accelerated by prekallikrein
Activation of X in the intrinsic pathway by?
VIII and IX
Steps on blood coagulation that do not need calcium
XII activating XI and XI activating IX
Function of citrate ion?
De-ionize calcium to stop coagulation in collected blood
Function of oxalate ion?
precipitate calcium out of solution to prevent clotting
Speed of two clotting pathways?
extrinsic is much faster then intrinsic
Three factors that prevent clotting in the normal endothelium?
- 1. smoothness of endothelium
- 2. layer of glycocalyx, mucopolysacharide
- 3. thrombomodulin and heparin on surface
Two function of thrombomodulin in anticoagulation?
- binds thrombin and removes it from circulation
- complex activates protein C which cleaves V and VIII and causes the release of t-PA
Two most powerful thrombin removers?
ATIII and fibrin mesh (prevents the spread of clot)
Largest site of heparin production?
mast cells, large amounts in lung and liver to stop the coagulation of slow moving venous blood
I, V, VIII, XII
Plasmin is caught in the fibrin mesh and combined into the clot
Disease or damage to what organ can cause bleeding problems
5 vit K dépendent coagulation factors?
II, VII, IX, X, protein c
Cause of vit K deficiency?
liver fails to secrete bile into the GI tract, obstruction of the bile duct or liver disease, prevents adqauate fat absorption
Inheritance of hemophilia A
two compound of factor VIII
factor VIII and von willebrands factor (protects factor 8 in circulation)
difference in bleeding with hemophilia a and thrombocytopenia?
thrombocytopenia is small vessels and hemophilia in large
spleenectomy and whole blood transfusion are helpful
- widespread clotting in the circulation
- usually occurs with large amounts of traumatized or dying tissue that releases tissue factor into the blood
- can remove many clotting factors and eventually cause bleeding
Clotting disorder with septicemia
DIC, caused by bacteria or endotoxins, part of the reason septic shock is lethal.
Time for warfarin effect
- 12 hours 50%
- 24 hours 20% clotting power
oxalate is toxic to the body
can citrated blood be re-infused
yes the liver will convert the citrate to glucose within a couple minutes
what is hyperemia?
increased blood flow to activated tissues
PT time is a measure of what?
concentration of prothrombin in the blood
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