Pathophys of Hemostasis

Question 1

What is primary hemostasis?

Answer 1

Step 1-vasoconstriciton: direct injury resulting in recruitment of chemical messenger from endothelial cells and platelets.
(Chemical Messengers: Thromboxane A2, serotonin, endothelin I–MOST potent vasoconstrictor)

Step 2-platelet plug formation, VonWillebrand factor is released, platelets are activated by vWF, platelet proteins on platelets bind to fibrinogen causing platelets to adhere.
–lasts 12-24 hrs

Question 2

What are some outer membrane proteins on thrombocytes?

Answer 2

-glycoproteins: GPIIb/IIIa binds fibrinogen to platelets.

• glycosaminoglycans
• coagulation proteins
• no nucleus

Question 3

Lifespan of platelets?

• platelets contain what?
• what regulates the production of thrombocytes?
• where are platelets produced?
• what do activated and non-activated platelets look like?

Answer 3

• lifepsan 8-12days
• serotonin, calcium, ADP, PDGF (platelet dereived growth factor), thromboxane A2
• Thrombopoietin from liver, kidney, smooth muscle, and bone marrow.
• look like potato chips in inactivated state and like spikey balls in the activated

Question 4

What activates the platelets?

Answer 4

vonwillibrand factor

Question 5

Describe the steps of platelet aggregation?

Answer 5

1. A tissue injury
2. B vWF released from endothelial cells at site of injury, recruits platelets.
3. platelet adhesion to vWF on endothelial wall.
4. ) vWF activates platelet and causing shape change.
5. ) once shape change, platelet release granules recruiting more platelets
6. ) aggregation (hemostatic plug) (collagenous)

Question 6

Platelet plug formation defective if?

Answer 6

• low platelets
• decreased vWF
• medications inhibiting platelets (ASA, clopidrogel)

Question 7

What is Secondary Hemostasis ?

Answer 7

• coagulation

* activated by either a defect in vessel endothelium or disruption in vessel wall

Question 8

How is the intrinsic pathway activated?

Answer 8

-initially exposed collagen in the vessel activates factor XII (Hageman Factor)

Question 9

what element is essential for the clotting cascade?

Answer 9

CALCIUM, for both intrinsic and extrinsic

Question 10

What factor starts the extrinsic pathway?

Answer 10

tissue factor (factor III)

Question 11

What activates tissue factor?

Answer 11

inflammatory cytokines, cell injury, and vessel injury (bleeding into the tissue)

Question 12

What starts the common pathway?

What ends the pathway?

Answer 12

starts with factor X, goes through prothrombin, thrombin, and figrinogen, and ends with the formation of fibrin

Question 13

How long does it take to complete clot formation?

Answer 13

3-6 minutes

Question 14

What is clot retraction?

Answer 14

Platelets contract and draw the edges of the blood vessel closer together

Question 15

What is necessary to remove clots as the blood vessels heal? When does this occur?

Answer 15

fibrinolysis is necessary to remove clots.

occurs within 2 days of clot formation and continues until the clot is fully dissolved.

Question 16

What is plasmins function?

What leads to the formation of plasmin?

Answer 16

• digests firbin in the clot to break it up.

- the formation of plasmin is dependent on the activation of plasminogen by tPA, XIIa, and thrombin from plasminogen.

Question 17

Where do tPA and urokinase come from? What causes their release?

Answer 17

• liver, plasma, and enodthelium

- release stimulated by vasoactive drugs, venous occlusion, increased body temp, and exercise.

Question 18

What regulatory mechanisms limit clot growth?

Answer 18

-removal of clotting factors with dilution (simple circulation)

• Inhibit activated clotting factors with:
• -antithrombin III (inactivates II and X)
• -Protein C (inactivates V and VII)
• -Protein S (accelerates the action protein C)
• -Heparin (inactivates II and ATIII)

Question 19

What are some nutritional deficiences and liver failure that can alter the ability to control hemostasis?

Answer 19

• Ca 2+ helps activate multiple clotting factors throughout the entire coagulation cascade
• Vit K is required fro synthesis of clotting factors II, VII, IX, and X, protein C, and prothrombin
• most of clotting factors are synthesized in the liver. Liver failure would be bad.