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19 Cards in this Set

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A mature megakarocyte gradually loses all of its cytoplasm, producing about 4000 platelets, before the nucleus is engulfed by phagocytes and broken down for recycling. TRUE/FALSE
TRUE.
What is interleukin-6?
It is a hormone that stimulates platelet formation.
The rate of megakaryocyte activity and platelet formation is stimulated by what?
Thrombopoietin. It is a peptide hormone produced in the kidneys and possibly other sites.
What are the three phases of hemostasis?
1. vascular phase
2. platelet phase
3. coagulation phase
In the vascular phase, endothelial cells begin releasing chemical factors. What are these?
ADP/ Tissue factor/Prostacyclin/Endothelins. They stimulate smooth muscle contraction and promote vascular spasm.
Regarding the Platelet phase, platelets begin releasing a wide variety of compounds which stimulate platelet aggregation. List several of them.
1.ADP
2.thromboxane A2
3.serotonin
4.clotting factors
5.platelet derived growth factor
6.calcium ions
What is prostacyclin?
It limits the growth of the platelet plug. It is a prostaglandin, that inhibits platelet aggregation.
Serotonin in high concentrations blocks the action of ADP. TRUE/FALSE
TRUE.
What are the three pathways of the coagulation phase?
1. Extrinsic
2. Intrinsic
3. Common
What does the extrinsic pathway begin with?
It begins with the release of factor 3(tissue factor) by damaged endothelial cells or peripheral tissues. It then combines with Ca+ and another clotting factor (factor 7) to form an enzyme complex capable of activating Factor X, which is the first step in the common pathway.
What does the Intrinsic pathway start with?
It begins with the activation of proenzymes(usually factor X11) exposed to collagen fibers at the injury site. This pathway proceeds with the assistance of PF-3(platelet factor). After a series of linked reactions, activated factors V111 and 1X combine to form an enzyme complex capable of activating factor X.
Where does the common pathway begin?
It begins when enzymes from either the extrinsic or intrinsic pathway activate factor X, forming the enzyme prothrombinase. This converts prothrombin into thrombin.
What does thrombin do?
Thrombin then completes the clotting process by converting fibrinogen to fibrin.
When a blood vessel is damaged both the extrinsic and intrinsic pathways respond. The extrinsic pathway is shorter and faster than the extrinsic pathways and it is usually the first to initiate clotting. TRUE/FALSE
TRUE.
List the 12 clotting factors involved in the pathways?
1. Factor 1- fibrinogen
2. 11- prothrombin
3. 111-tissue factor
4. 1V- calcium ions
5. V- proaccelerin
6. V1- (no longer used)
7. V11 proconvertin
8. V111- antihemophilic
9. 1X- plasma thromboplastin
10. X- Stuart-Prower factor
11. X1. plasma thromboplastin
12. X11- hageman factor
13. X111- fibrin stabilizing
List 5 anticlotting factors?
1. antithrombin 111
2. heparin- released from basophils and mast cells
3. thrombomodulin- released by endothelial cells.
4. prostacyclin
5. alpha-2-macroglobulin.
What is protein C?
It is a plasma protein that inactivates several clotting factors and stimulates the formation of plasmin(breaks down fibrin strands)
What is syneresis?
It is another term for clot retraction.
How does fibrinolysis begin?
It begins with the activation of the proenzyme plasminogen by two enzymes:
thrombin/tissue plasminogen factor released by damaged tissues. Plasminogen produces the enzyme plasmin, which digests fibrin strands.