Lecture 27: Hemostasis

Question 1

What is another name for platelets?

Answer 1

Thrombocytes

Question 2

From where are platelets derived?

Answer 2

Megakaryoctyes

Question 3

What are platelets’ three simples to create a plug?

Answer 3

1. Adhesion
2. Activation
3. Aggregation

Question 4

What controls the process of platelet production?

Answer 4

Thrombopoietin: stimulates platelet production

• If too many platelets, TPO decreases
• If too few platelets, TPO increases

Question 5

What produces thrombopoietin?

Answer 5

Liver

Kidney

Question 6

Where does thrombopoietin bind?

Answer 6

c-MPL (CD-100) receptor

-found on megakaryocytes and platelets

Question 7

What is hemostasis?

Answer 7

Preventing and stopping bleeding

-keep blood within a damaged blood vessel

Question 8

What are the four basic steps of hemostasis?

Answer 8

1. Vascular spasm (contraction)
2. Formation of platelet plug
3. Formation of blood clot
4. Repair of damage

Question 9

Why is vasospasm important in hemostasis?

Answer 9

Disrupts blood flow and prevent further blood loss

Question 10

How does vasospasm occur in hemostasis?

Answer 10

1. Myogenic contraction
2. Platelet factors: serotonin, thromboxane A2 promote vasoconstriction
3. Release of molecules from endothelial cells
4. Neural reflex for spasm to occur

Question 11

Where do platelets attach to on an injured blood vessel?

Answer 11

Negative charges on collagen and laminin

Question 12

What specific receptors allow platelets to adhere to each other and the endothelial cells?

Answer 12

Von Willebrand Factor (vWF)

Collagen (Gp Ia/IIa)

Question 13

What is released from dense granules in platelets when they are activated?

Answer 13

ATP and ADP
Serotonin
Calcium

Question 14

What is released from α granules in platelets when they are activated?

Answer 14

Growth factors
Von Willebrand Factor (vWF)
Factor V
Fibrinogen

Question 15

What factors from platelets promote aggregation?

Answer 15

ADP
Serotonin
Thromboxane A2

Question 16

What is the role of fibrinogen?

Answer 16

When it is activated as fibrin, it helps form platelet plug

Question 17

How does aspirin work?

Answer 17

Inhibits clotting by reducing release of thromboxane A2 from platelets

Question 18

How does Plavix (clopidogrel) work?

Answer 18

Inhibits P2Y12 receptors to prevent further platelet activation and aggregation

Question 19

What activates fibrinogen?

Answer 19

Thrombin (activated form of pro-thrombin)

Question 20

What is the role of platelet derived growth factor?

Answer 20

Stimulates fibroblasts to grow into the damaged area and differentiate into smooth muscle

Question 21

How are clots removed?

Answer 21

Plasmin: lysis fibrin and fibrinogen

Question 22

What limits clotting?

Answer 22

Fibrin: inhibits thrombin
Prostacyclin: limits platelet aggregation
Antithrombin II: anticoagulant
Heparin: anti-thrombin from mast cells

Question 23

What are some hallmarks of the extrinsic pathway?

Answer 23

Activated by external trauma and prevents blood to escape vascular system
-Factor VII

Question 24

What are some hallmarks of the intrinsic pathway?

Answer 24

Activated by internal trauma, platelets, exposed endothelium

-Factors XII, XI, IX, VIII

Question 25

What are some hallmarks of the common pathway?

Answer 25

Finish pathway of clot producition | -Factors I, II, V, X

Question 26

What factors do Vitamin K antagonists affect?

Answer 26

Factors II, VII, IX, X | -cofactor for the synthesis of these

Question 27

What do Vitamin K antagonists do?

Answer 27

Prevents blood clots

Question 28

What is the difference between primary and secondary hemostasis?

Answer 28

Primary has a weaker platelet plug | Secondary has strong plug with fibrin mesh

Question 29

What factors does thrombin activate?

Answer 29

1. Fibrinogen --> Fibrin 2. Factor XIII --> Factor XIIIa 3. Factor VIII --> Factor VIIIa 4. Factor V --> Factor Va

Question 30

What factor allows fibrin to cross link?

Answer 30

Factor XIIIa

Question 31

What are the two types of oral anticoagulants?

Answer 31

Hydroxycoumarins (Warfarin/Coumadin) and Indanediones | -Vitamin K antagonists

Question 32

What does warfarin target?

Answer 32

Vitamin K epoxide reductase | -prevents reduction of Vitamin K after its oxidized

Question 33

Which is more potent: R-Warfarin or S-Warfarin?

Answer 33

S-warfarin

Question 34

What are the roles of Protein C and S?

Answer 34

Anti-coagulants - inactivates Factor Va and VIIIa - Protein C promotes plasmin by inhibiting its inhibitor

Question 35

In Hemophilia A, what factor is deficient or absent?

Answer 35

Factor VIII

Question 36

In Hemophilia B, what factor is deficient or absent?

Answer 36

Factor IX

Question 37

What does prothrombin time (PT) evaluate?

Answer 37

Extrinsic Coagulation Pathway - Factors I, II, V, VII, and X - normal: 12-13 sec

Question 38

What does partial thromboplastin time (PTT) evaluate?

Answer 38

Intrinsic and Common Clotting Pathway - Factors XII, XI, IX, VIII, X, V, II, I - normal: 30-50 sec

Question 39

If PT is prolonged and PTT is normal, what can that mean?

Answer 39

Liver disease | -something wrong with Factor VII

Question 40

If PTT is prolonged and PT is normal, what can that mean?

Answer 40

Issue with a intrinsic pathway factor of vWF disease

Question 41

If both PT and PTT are prolonged, what can that mean?

Answer 41

- Issue with common pathway factors - Warfarin overdose - Severe liver disease