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Factor released by platelets to cause vasoconstriction?
Thromoxin A2
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Four mechanisms to hemostasis?
- 1. vascular constriction
- 2. platelet plug
- 3. blood coagulation
- 4. growth of fibrous tissue
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Contactile fibers contained in platelets
actin, myosin, thombosthenin
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Ion stored by platelets?
Calcium, dence granual
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Functions of platelet derived growth factor
causes vascular smooth muscle, vascular endothelial cells, and fibroblasts to grow and multiply
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Molecule on platelet surface that activates clotting (generic)
phospholipids
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Half life of platelets and method of distraction
8-12 days, tissue macrophages, mainly spleen
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when platelets bind to the endothelium what causes the release of granolas?
contraction
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three location of vWF
platelets, endothelium, circulation
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Two secretions of platelets that activate more platelets?
ADP, thromboxan A2
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Loose plug
platelets only
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Responsible for plugging thousands of vascular holes daily?
platelts
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major functional unit of clot retraction?
platelets
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Two outcomes of a blood clot?
- 1. can be invaded by fibroblasts and form connective tissue, promoted by PDGF, 1-2 weeks
- 2. dissolve
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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
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Prothrombin activator is formed in result of?
- vascular damage
- damage to special substances in the blood
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Name and function of GPIIb/IIIa?
prothrombin receptor, on the cell membrane of platelets already bound to damaged tissues
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2 alpha-2-globulins
prothrombin and bradykinin
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Does fibrinogen leak of of vessels?
- no, it is too large.
- During pathological conditions vascular permeability can increase enough to let it out
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Reticulum of a blood clot?
Long fibrin chain attached to clot
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Fibrin stabilizing factor, site of storage and function.
released by activated platelets and cross links fibrin monomers by covalent bonds
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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
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Failure of a clot to retract indicates?
low platelet level
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Platelets release what that cause clot contraction?
ATP and calcium to activate actin/myosin and thrombosthenin
-
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factors activated thrombin act on
2, 8, 9, 10,11, and 12
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three initiating events of prothrombin activator formation
- 1. trauma to vascular wall
- 2. trauma to blood
- 3. contact of blood with collagen
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Two pathways of prothrombin activator?
- Intrinsic- damage to blood
- Extrinsic-damage to vascular wall
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Factor that activates prothrombin activator?
Xa
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What is released form damaged blood vessels to initiate the extrinsic pathway?
tissue factor, tissue throboplastin
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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
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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
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Cleavage of XI by XII needs?
HMW kininogen, accelerated by prekallikrein
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Activation of X in the intrinsic pathway by?
VIII and IX
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Steps on blood coagulation that do not need calcium
XII activating XI and XI activating IX
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Function of citrate ion?
De-ionize calcium to stop coagulation in collected blood
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Function of oxalate ion?
precipitate calcium out of solution to prevent clotting
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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
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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
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Two most powerful thrombin removers?
ATIII and fibrin mesh (prevents the spread of clot)
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Largest site of heparin production?
mast cells, large amounts in lung and liver to stop the coagulation of slow moving venous blood
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Plasmin substrates?
I, V, VIII, XII
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Plasmin is caught in the fibrin mesh and combined into the clot
-
Disease or damage to what organ can cause bleeding problems
liver
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5 vit K dépendent coagulation factors?
II, VII, IX, X, protein c
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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
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Inheritance of hemophilia A
x linked
-
two compound of factor VIII
factor VIII and von willebrands factor (protects factor 8 in circulation)
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difference in bleeding with hemophilia a and thrombocytopenia?
thrombocytopenia is small vessels and hemophilia in large
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thrombocytopenia purpura
spleenectomy and whole blood transfusion are helpful
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DIC?
- 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.
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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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