Clotting Cascade and hemostasis Flashcards
What are the steps from tissue injury to the common pathway for the extrinsic pathway?
Tissue Injury
Factor III (Tissue Factor) released
Tisue factor turns Factor VII into Factor VIIa
Factor VIIa turns Factor X into Factor Xa
Which factors are vitamin K dependent?
Factors II, VII, IX, X
What all makes up prothrombinase?
Factor Va
Factor Xa
Ca2+
What is the role of thrombin in the polymerization of fibrin?
It activates Factor XIII, which crosslinks fibrin polymers to form “stable fibrin.”
Thrombin catalyzes the activation of which two factors?
Factor V and Factor VIII
What lab test primarily tests the extrinsic and common pathway?
What factors of the extrinsic pathway are tested?
Prothrombin time
Just VII
What lab test primarily tests the intrinsic and common pathway?
Activated partial thromboplastin time
(Remember that kaolin is used for the negative surface in activated partial thromboplastin time tests.)
What test measures the activity of Heparin?
Activated partial thromboplastin time
Which factors are inhibited by heparin?
II, IX, and Xa
What pathway is activated by trauma inside vasculature?
Outside trauma?
Which is faster?
1) Intrinsic
2) Extrinsic
3) Extrinsic
Which factors are inhibited by coumadin?
The ones that use Vitamin K
II, VII, IX, X
Where is thrombopoietin produced?
What does it do?
1) It is produced by the liver and to a lesser extent, the kidney.
2) Controlls platelet production
If platelet levels drop, what happens to TPO levels?
What does TPO bind to on platelet, megakaryocytes, and hematopoietic stem cells?
1) Increases
2) MPL (CD-110)
What is the function of cyclooxygenase 1?
Conversion of arachidonic acid into prostaglandins (like thromboxane A2)
What limits blood loss after tissue injury?
Hemostasis
What are the four steps of hemostasis?
Vascular spasm
Platelet plug
Blood clot
Repair
In what step in hemostasis is there an activaiton of fibrin by thrombin and the fibrin squeezes together with the help of calcium for clot retraction?
What step does vascular smooth msucle contract on its own and serotonin and thromboxane a2 released from platelets?
What step does von Willebrand factor released from damaged cells to help initiate platelet collagen binding?
What step do platelts secrete platelet derived growth factor to stimulate fibroblast growth/differentiation into smooth muscle?
1) Step 3: Blood Coagulation
2) Step 1: Vascular spasm
3) Step 2: Platelet plug formation
4) Step 4: Damage Repair
What three chemicals act as short term vasoconstrictors to assist with the vascular spasm phase of hemostasis?
Thromboxane A2
Platelet factor
Serotonin
What are the two steps for the formation of a platelet plug?
- Collagen is exposed -
Step 1: Von Willebrand factor binds
Step 2: Platelet’s collagin receptor binds and is activated
What does thrombin do to help form a clot?
What does it do to get rid of a clot?
1) To form the clot: fibrinogen → fibrin
2) To get rid of the clot,
Protein C → Activated protein C
What is the function of protein C in clot removal?
What does this allow?
1) It inactivates the tPA inhibitor
2) Tissue plasminogen activator (tPA) to activate plasminogen into plasmin.
What is the main mechanism of anticoagulants such as warfarin?
Inhibition of vitamin K action
If a clot produces a small drop of clear fluid that has risen to the surface of the clot, what is the cause?
Actin/myosin cross linking (step 3 of hemostasis)
Wita full coagluation panel, if aPTT is elevated at 45 seconds, PT is normal at 12 seconds, and platelet levels are normal, what is likely deficient in this patient?
Factor IX - intricisic pathway
A patient with Factor V mutation will have what lab results?
Why?
Prolonged aPTT, PT, normal platelet count
Factor V is part of common pathway
What is occuring in your body when a cut has healed and the scab is starting to fall off?
T-PA is converting plasminogen to plasmin
Excessive use of alcohol has what affect on platelet count?
Decreases because TPO is produced in liver
Platelets are derived from?
Megakaryocytes
What blocks formation of platelet plug?
How?
1) Aspirin
2) Reduces release of thromboxane A2 (COX inhibitor)
What is made by injured endothelial cells and limits platelet aggregation?
What is an anticoagulant when bound to thrombin?
1) PG12
2) Antithrombin III
If a patient with recurrent DVT was placed on Warfarin what may be the cause of their condition?
Protein C deficiency
