Hemostasis Intro 1

Question 1

What is the converging factor between the 2 pathways?

Answer 1

factor X

Question 2

Why is it called the extrinsic pathway?

Answer 2

requires tissue factor to function

Question 3

Why is it called the intrinsic pathway?

Answer 3

the components are contained w/I the plasma

Question 4

How is the extrinsic pathway initiated?

Answer 4

tissue factor binds to factor VIIa

Question 5

How is the intrinsic pathway initiated?

Answer 5

contact factors activate factor XI

Question 6

What are the contact factors?

Answer 6

factor XII, prekallikrein, HMWK

Question 7

What is the common pathway?

Answer 7

events after activation of factor X (the convergence)

Question 8

Intrinsic pathway steps?

Answer 8

activation of contact factors, leading to activation of factor XI, then activation of factor 9, then with cofactor VIIIa activation of factor X, then with cofactor Va, activate factor II, converting fibrinogen to fibrin

Question 9

Where are the proteins of the coagulation cascade synthesized?

Answer 9

in the liver

Question 10

What is bleeding diathesis?

Answer 10

bleeding tendency or predisposition

Question 11

What are the exceptions to liver production of coagulation cascade proteins?

Answer 11

1. tissue factor (surface of many cells)

2. VWF (endothelial cells and megakaryocytes)

Question 12

Where is tissue factor synthesized?

Answer 12

Q

on the surface of many cells

Question 13

Where is VWF synthesized?

Answer 13

endothelial cells and megakaryocytes

Question 14

Where is factor VIII produced?

Answer 14

the liver, spleen, lung, kidney

Question 15

What does the suffix “a” indicate?

Answer 15

the activated form

Question 16

Which factor has the shortest half life? Why is this important?

Answer 16

factor VII; it’s one of the first factor to deplete in disease

Question 17

Almost all of the enzymes in the coagulation cascade are _____.

Answer 17

serine proteases

Question 18

Inactive precursor proteins are called ____.

Answer 18

zymogens

Question 19

Zymogens that become active serine proteases include ____ (7).

Answer 19

1. factor XII (12)
2. prekallikrein
3. factor XI (11)
4. factor IX (9)
5. factor X (10)
6. factor VII (7)
7. factor II (2- prothrombin)

Question 20

Which are the vitamin-K dependent factors? (6)

Answer 20

1. factor II (2)
2. factor VII (7)
3. factor IX (9)
4. factor X (10)
5. anticoagulant protein C
6. protein S

Question 21

What do the vitamin-K dependent factors have in common?

Answer 21

Gla domains that bind Ca++ to cause conformational change of protein into active form

Question 22

Why is factor XIII (13) unique? What does it do?

Answer 22

enzyme that is not a serine protease- it’s a transglutaminase; covalently links fibrin molecules together to form a stable clot

Question 23

Why are cofactors important in the coagulation cascade?

Answer 23

they initiate and accelerate enzymatic rxns by bringing components together and orienting them correctly

Question 24

Name the cofactors in the coag. cascade. (4)

Answer 24

1. tissue factor
2. factor VIII (8)
3. factor V (5)
4. HMWK

Question 25

What protein makes the actual clot?

Answer 25

fibrinogen

Question 26

What does VWF stand for?

Answer 26

von Willebrand Factor

Question 27

What does VWF do?

Answer 27

it’s the carrier protein for factor VIII (8) in the plasma

Question 28

Where is VWF produced and stored?

Answer 28

Weibel-Palade bodies in endothelial cells and in alpha-granules of platelets

Question 29

Why does VWF bind to factor VIII (8)?

Answer 29

to protect it (prolong its half life)

Question 30

What happens in VWF-deficient pts?

Answer 30

Q

low levels of circulating factor VIII (8), leading to a bleeding disorder similar to hemophilia A

Question 31

What do enzyme complexes consist of?

Answer 31

protease + cofactor + phospholipid surface + Ca++

Question 32

Extrinsic pathway steps?

Answer 32

tissue factor binds to factor VIIa, which activates factor X, Xa with cofactor Va activates factor II to IIa, which then converts fibrinogen to fibrin