Hemostasis Flashcards
1
Q
What does TPO do?
A
- Actiavates production of platelets
- Binds to c-MPL on megakaryocytes and other hematopoeitic cells
2
Q
How is TPO secretion controlled?
A
- Controlled by itself and platelets themselves
3
Q
WHat happens to TPO if you have high # of platelets?
A
- TPO bounnd to c-MPL receptor, internalized, anddegraded in platelets and megakaryocytes
- Little TPO is free
4
Q
What happens to TPO if you have low number of platelets?
A
- Little TPO is bound to c-MPL receptor and is not ddegraded
- High TPO free
5
Q
What are the four steps to hemostasis?
A
- Vasuclar spasm
- Formation of platelet plug
- Formation of blood clot
- Repair of damage
6
Q
What is the purpose of vasospasm?
A
- Disrupsts blood flow to keep blood above the spasm and avoid further blood loss
7
Q
What factors cotnribute to the vasospasm?
A
- Myogenic
- Platelet factors-serotonin & thromboxane A2
- Release of molecules from endothelieal cells
- Neural reflex
8
Q
How does platelet plug adhesion occur
A
- Initiated by activation of latelet receptors such as glycoprotein Ib/Ia
9
Q
What are ligands for plateleet receptors?
A
- Von willebrand factor: released from endothelial cells and platelets
- Collagen (Gp Ia/IIa) fibronectin and laminin (Gp Ic/IIa) under the endothelial layer
10
Q
What happens after activation of platelet receptors?
A
- Activation of phospholipase C and Calciumm influx
- Release of ATP ADP serotonin and Ca from dense granules
- Release GF, vWF, factor V and fibrinogen from alpha granules
- Finger like filopodia extension
- Generation fo thromboxane A2 from archidonic acid by cyclooxgenase
11
Q
What does ADP bind?
A
- P2Y12 receptors on platelets which causes conformational change in Gp IIb/IIIa
- Now platelet can bind fibrinoge4n which forms aggregation of platelets allowing the platelet plug to form
12
Q
What does aspirin inhibit?
A
Its a cyclooxygenase inhibitor that inhibits clotting by reducing release of thromboxane A2
13
Q
Blood clot formation? Activation of prothrombin & Fibrinogen?
A
- Activated by factor 5 and Ca to Thrombin
- Generation of fibrin from fibrinogen
- Fibrin polymerization and contarction of clot (requires Ca)
14
Q
How does the vessel wall get repaired?
A
- Platelets secrete platelet derived growth factor which stimulates fibroblasts to grow into area and differentiate into smooth muscle
15
Q
How are clots broken down?
A
- Plasmin
- Activated by tissue plasminogen activator
- Resleased by damage tissue
- protein C inactivates inhibitior of t-PA
- Plasmin is responsible for lysis of clot
