Introduction to Hemostasis Part I

Question 1

What is primary hemostasis?

Answer 1

What the platelets are doing in hemostasis. (clot formation)

Question 2

What is secondary hemostasis?

Answer 2

What the clotting factors are doing in hemostasis. (clot stabilization)

Question 3

What is the key component of the extrinsic pathway and why?

Answer 3

Tissue Factor. it is released and leads to fibrin accumulating and forming a more stable plug than the one found in primary hemostasis

Question 4

people with hemophilia have a normal what?

Answer 4

PT

Question 5

What are contact factors?

Answer 5

Prekallikrein, factor VII, HMWK

Question 6

What are the basic steps in primary hemostasis?

Answer 6

breach in endothelium exposes collagen. vWF (von willebrand factor) binds collagen. Platelets have special receptor for vWF and bind there. Platelets stick to vWF and are activated. Activated platelets release coagulation stuff (ADP and TXA2). They also begin to express receptor for fibrinogen. Fibrinogen helps platelets aggregate.

Question 7

Which factors are Vitamin K dependent?

Answer 7

II, VII, IX, X,

Question 8

Which factors are proteases?

Answer 8

VII, XII, XI, IX, VIII, X, II, XIII Prekallikrein. Everything except V and fibrin

Question 9

Which factors are soluble cofactors?

Answer 9

Tissue Factor, VIII, V, HMWK

Question 10

Which factor has shortest half life?

Answer 10

VII

Question 11

What kind of protease is factor XIII?

Answer 11

transglutaminase. All other proteases are serine proteases.

Question 12

serine protease cleave at _______ (target) and thus activate enzymes. Thus these enzymes are ______.

Answer 12

arginine residues.

zymogens

Question 13

Vitamin K is required for post translational modification of which factors?

Answer 13

2, 7, 9, 10, C and S.

Question 14

Hemorrhagic disease of the newborn is due to _______ deficiency.

Answer 14

Vit. K

Question 15

warfarin is a competitive inhibitor for what?

Answer 15

Vit. K

Question 16

Almost all blood factors are made in the ______ except which ones?

Answer 16

liver.
Tissue Factor
Factor VIII (made in many places)
vWF (made in megakaryocytes and endothelial cells)

Question 17

what is the basic 2 step process of coagulation?

Answer 17

• prothrombin + thromboplastin + calcium =thrombin

- Fibrinogen + Thrombin = fibrin

Question 18

What are the modern phases of coagulation?

Answer 18

1. Initiation
2. Amplification
3. Propagation

Question 19

Amplification phase takes place on __________

Answer 19

surface of platelets which have adhered to the exposed subendothelium and been activated.

Question 20

A phospholipid surface is provided by the ________

Answer 20

platelet surface

Question 21

What is the extrinsic tenase and what does it activate?

Answer 21

Factor VIIa, Tissue factor.

It activates factor X, IX, and more VII

Question 22

What is prothrombinase?

Answer 22

Factor Va, Factor Xa which activates factor II (changes prothrombin to thrombin)

Question 23

What is special about activated factor X in the initiation phase?

Answer 23

it can generate small amounts of thrombin without the prothrombinase complex

Question 24

Describe the initiation phase.

Answer 24

Factor VIIa and tissue factor (extrinsic tenase) activate factors IX, X and VII. Factor Xa then goes on to generate a little active factor II (thrombin) which gets the whole process rolling.

Question 25

Describe the Amplification phase

Answer 25

activated factor II from initiation phase goes and activates factor V, factor VIII (cofactor for intrinsic tenase), and factor XI which will go on to activate factor IX (also important for the intrinsic tenase).

Question 26

What is the intrinsic tenase?

Answer 26

factor VIIIa, factor IXa which activates factor X.

The instrinsic tenase activates much more factor X than the extrinsic tenase.

Question 27

Describe the propagation phase.

Answer 27

formation of the intrinsic tenase allows for activation of factor X. Factor X binds to prothrombinase and activates factor II. Factor IIa clips peptides off of fibrinogen to form fibrin which then can aggregate (noncovalently) with other fibrin molecules and create network. Thrombin also activates Factor XIII which forms covalent bonds between the D domains of fibrin molecules

Question 28

How do fibrin molecules aggregate?

Answer 28

non-covalently at first, matching up D domain on the ends of the molecule with the E domains in the middle of another fibrin molecule.

Question 29

Factor IIa is the central figure in the clotting cascade. What are all the things it activates?

Answer 29

Fibrinogen-->Fibrin
Factor V and VIII
Factor XIII
Factor XI
It is a potent platelet activator
Plays a role in anticoagulation and fibrinolysis.