lec 8 : Natural Anticlotting & Fibrinolytic System

Question 1

Anti-Clotting Mechanisms

Answer 1

• Rapid flow of blood
• Endothelial factors
• Anticoagulant proteins
• Thrombin Removal from Blood
• Heparin
• Clot Lysis

Question 2

Endothelial Factors for Anti-Clotting

Answer 2

• smooth endothelium
• glycocalyx on endothelium
• Balance between prostacyclin (PGI2) and thromboxane A2
• Thrombomodulin
• Tissue factor pathway inhibitor (TFPI)

Question 3

Smooth Endothelial Lining of the Blood Vessel

Answer 3

Prevents activation of intrinsic pathway & platelets

Question 4

Balance between Prostacyclin (PGI2) & Thromboxane A2 (TxA2) lead to ……………………

Answer 4

Keeps clot formation at site of injury only and rest of vessel lumen free of clot

Question 5

Thrombomodulin-thrombin complex activates ……………………. that act as anticoagulant

Answer 5

protein C

Question 6

Tissue Factor Pathway Inhibitor (TFPI) made by ……………………Inactivates………….. ,……………………….

Answer 6

made by the endothelial cell.
•Inactivates
♣ Tissue factor / factor VIIa complex
♣ Factor X

Question 7

Anticoagulant Proteins

Answer 7

• Protein C (PC)
• Protein S
• Antithrombin III

Question 8

The activation of protein C is enhanced by …………………….. which acts as a cofactor.

Answer 8

protein S

Question 9

Activated Protein C (APC)

Answer 9

Inactivates active factors VIII, V
Inactivates inhibitors of plasminogen
activators
↑ formation of plasmin → helps lysis of fibrin

Question 10

• Is vitamin K-dependent hemostatic protein

Answer 10

protein S

Question 11

PC cofactor

Answer 11

protein S

Question 12

Anti-thrombin III (Heparin cofactor I)

Answer 12

• Inactivation of thrombin
• Inactivation of active factors II, IX, X, XI, XII
• Its action is facilitated by heparin

Question 13

Thrombin Removal from Blood Is mediated by

Answer 13

Fibrin fibers

Antithrombin III

Question 14

……………………% of thrombin is bound to fibrin,

► Remaining amount is bound to ……………………..

Answer 14

85 –90% ,

antithrombin-III.

Question 15

Heparin + Antithrombin III complex

→……………………………………………………………………………

Answer 15

→ Removal of thrombin & active factors XII, XI, X, IX

Question 16

Clot lysis is mediated by ………………………

Answer 16

Fibrinolytic system

Question 17

Plasminogen (profibrinolysin)
•Is an…………………………..
•Produced by……………..
•Circulates in plasma as a……………………

Answer 17

• inactive globulin
• liver
• plasma protein

Question 18

Plasminogen is converted to plasmin (fibrinolysin) by

Answer 18

♠ Thrombin
♠ Tissue plasminogen activator 
(t-PA) is released very slowly from damaged 
tissues and vascular endothelium
♠ Urokinase plasminogen activator
(u-PA)

Question 19

Plasmin is a proteolytic enzyme that digests

Answer 19

♣ Fibrin and fibrinogen
→ fibrin degradation products (FDP)
→ inhibit thrombin
♣ inhibit→ Prothrombin, factor V, factor VIII and factor XI

Question 20

function fibrin degradation products (FDP)

Answer 20

•Inhibits thrombin
•Inhibits interaction between fibrinogen &
thrombin
•Inhibits platelets activation and aggregation

Question 21

•APC along with its cofactor PS inactivates:

Answer 21

♦ Active Factors V & VIII
♦ Inhibitors of t-PA
→ increase formaCon of plasmin

Question 22

Thrombomodulin-thrombin complex activates…………….

Answer 22

protein C

Question 23

inactivates factor V and VIII?

Answer 23

Protein C

Question 24

The action of which one of the following is enhanced by heparin?

Answer 24

ATIII

Question 25

vitamin K synthesis factors ……… , ……….. , …………….., …………….

Answer 25

II , VII , IX , X