Hemostasis and coagulation

Question 1

What is hemostasis?

Answer 1

Prevention of blood loss

Question 2

What are the general steps of hemostasis?

Answer 2

Vascular constriction
Formation of platelet/primary plug
Formation of blood clot/secondary plug
Clot retraction and dissolution
Growth of fibrous tissue into the blood clot

Question 3

What causes vasoconstriction in response to trauma?

Answer 3

Local myogenic spasm/contraction
Release of vasoconstrictors from platelets

Question 4

What are the histological features of platelets?

Answer 4

Very small
No nucleus

Question 5

What stimulates platelet production?

Answer 5

Thrombopoietin

Question 6

What inhibits platelet activation?

Answer 6

Prostacyclin produced by endothelial cells

Question 7

What is a potent inducer of platelet activation?

Answer 7

TXA2/thromboxane

Question 8

What are the steps of platelet plug formation?

Answer 8

Adhesion
Activation
Aggregation

Question 9

What mediates platelet adhesion?

Answer 9

Platelet receptors/glycoproteins bind to vWF on endothelial cells

Question 10

What molecules released or produced from activated platelets help with platelet aggregation?

Answer 10

ADP
Serotonin
Thrombaxin

Question 11

How does aspirin work?

Answer 11

It inhibits clycooxygenase and decreases the release of thrombaxin

Question 12

What platelet receptors bind to vWF?

Answer 12

Gp 1b/1a

Question 13

What platelet receptors bind to fibrinogen?

Answer 13

Gp IIb/IIa

Question 14

What forms bridges between platelets?

Answer 14

Fibrinogen

Question 15

What normally occurs to activate procoagulants?

Answer 15

Injury to endothelial cells
Failure of endothelial cells to produce anticoagulant factors
Activation of platelets

Question 16

When does a clot start developing after trauma?

Answer 16

Within 15 to 20 seconds

Question 17

What does a clot begin to retract?

Answer 17

After 20 to 60 minutes

Question 18

What clotting factors require vitamin K?

Answer 18

Factor II, VII, IX, X

Question 19

What anticoagulants require vitamin K?

Answer 19

Protein C
Protein S

Question 20

What activates protein C?

Answer 20

Thrombomodulin

Question 21

How does Warfarin work?

Answer 21

Inhibits VKOR from reactivating vit K

Question 22

What activates the intrinsic pathway of coagulation?

Answer 22

When blood comes into contact with a negatively charged surface

Question 23

What activates the extrinsic pathway of coagulation?

Answer 23

When blood comes into contact with material from damaged cells
Tissue factor activation

Question 24

What is the function of thrombin?

Answer 24

Catalyzes the proteolysis of fibrinogen to fibrin
Activates factor XIII
Catalyzes the formation of new thrombin
Catalyzes the formation of Va and VIIIa

Question 25

What is the function of factor XIII?

Answer 25

Mediates formation of stable fibrin

Question 26

What can be indicated by failure of clot retraction?

Answer 26

Low platelets

Question 27

What activates and accelerates contraction during clot retraction?

Answer 27

Thrombin Calcium ions

Question 28

What molecules in platelets lead to strong contraction during clot retraction?

Answer 28

Thrombosthenin Actin Myosin

Question 29

What increases the levels of circulating t-PA?

Answer 29

Bradykinin Catecholamines

Question 30

What are the paracrine factors?

Answer 30

Prostacyclin NO

Question 31

What is the function of prostacyclin?

Answer 31

Vasodilation Inhibits platelet activation

Question 32

What is the general time frame to change a clot into fibrous tissue?

Answer 32

1 to 2 weeks

Question 33

What is the cessation of bleeding dependent on when testing bleeding time?

Answer 33

Adequate number of platelets Ability of platelets to adhere to vWF and fibrinogen Ability of the platelets to aggregate

Question 34

What is pathway is assessed by PT?

Answer 34

Extrinsic pathway

Question 35

What factors are assessed by PT?

Answer 35

Factors VII, X, II, V, and fibrinogen

Question 36

What pathway is assessed by PTT?

Answer 36

Intrinsic pathway

Question 37

What factors are assessed by PTT?

Answer 37

Factors XII, XI, IX, VIII, X, V, II, and fibrinogen