Hemostasis

Front 1

Name three things that can activate procoagulant substances.

Back 1

1. Tissue injury

2. Blood vessel rupture

3. Trauma to the blood (i.e. sepsis)

Front 2

____________ on platlets adhere to subendothelial _____________

Back 2

GPIa receptors

Subendothelial collagen

Front 3

What is von Wildebrand factor?

Back 3

A substance that leaks from the plasma into damaged tissue.

Adhere to GP1b receptors on platlets

Front 4

Adherence to the vessel wall stimulates platlets to: (2)

Back 4

Release thromboxane A2 (TXA2) and degranulate

Front 5

Name two functions of TXA2

Back 5

Promotes platlet aggregation

Potent vasoconstrictor

Front 6

What substances are released during degranulation?

Back 6

Dense granules release: (pro-aggregants)

ADP, 5-HT, Histamine, and Calcium

Alpha granules release:

vWF, fibrinogen, factors (V, VII, XI, XIII), PAI-1

Front 7

How does platlet aggregation occur?

Back 7

Fibrinogen binds to GPIIb/IIIa receptors and promotes aggregation.

Front 8

The intrinsic pathway is also known as the ___________ pathway and is triggered via ______

Back 8

Contact activation pathway

Contact activation of factor XII with collagen

Front 9

Describe the steps of the contact activation pathway

Back 9

1. Collagen activates factor XII

2. Factor XIIa activates factor XI

3. Factor XIa activates factor IX [TF-VIIa also activates factor IX]*

4. Factor IXa activates binds factor VIIIa to form the tenase complex.

5. Factor IXa-VIIIa complex (tenase) activates factor X

*From extrinsic pathway

Front 10

The extrinsic pathways is also known as the ____________ pathway. Why?

Back 10

Tissue factor pathway

Front 11

What is the role of tissue factor (TF)?

Back 11

Found in nonvascular cell membranes and the membranes of damaged endothelium.

TF activates factor VII

Front 12

Describe the extrinsic pathway (Tissue Facor pathway)

Back 12

TF activates factor VII.

Factor VIIa-TF complex activates factor X

Front 13

What are the steps of the final common pathway?

Back 13

Factor Xa binds factor V

Factor Xa-Va complex activates prothrombin (Factor II) *

Thrombin (IIa) activates fibrinogen (FI) to form Fibrin (Ia)

*TF-Va complex also activates factor IX

Front 14

In addition to activating fibrin, thrombin plays an important positive feedback role.

Name four positive feedback roles of thrombin.

Back 14

1. Further platlet activation

2. Further activation of factor V

3. Release of factor VIII from vWF & activation of factor VIII

4. Activation of factor XI

Front 15

Prothrombin (factor II) is synthesized in the __________ and requires __________

Back 15

Liver

Vitamin K

Front 16

What is the role of calcium in the coagulation cascade?

Back 16

Required for the activation for factor IX

Required for activation of factor X (both pathways)

Required to form Va-Xa complex (prothrombinase complex)

Required for activation of thrombin.

Front 17

How is fibrin stabilized?

Back 17

Thrombin activates factor XIII (also known as fibrin stabilizing factor)

Factor XIIIa stabilizes fibrin

Front 18

Vitamin K is required for the synthesis of which clotting factors?

Back 18

Factor II (Prothrombin)

VII

IX

X

Front 19

Where is vitamin K synthesized?

Back 19

In the intestine by bacteria

Front 20

How does the endothelial surface prevent clot formation?

Back 20

1. Prevents contact activation (intrinsic pathway)

2. Glycocalix repels clotting factors and platlets

3. Thrombomodulin (endothelial membrane receptor) binds thrombin

Front 21

What is the role of antithrombin III?

Back 21

Removes thrombin and other clotting factors from the blood.

Front 22

How does heparin work?

Back 22

Enhances the action of antithrombin III

by a thousand fold

Front 23

What is the role of proteins C and S?

Back 23

Proteins C and S inactivate factors Va and VIIIa

Front 24

Proteins C and S require _________ for synthesis

Back 24

Vitamin K

Front 25

____________ trapped in the fibrin clot is activated by __________ to become _________

Back 25

Plasminogen

tPA

Plasmin

Front 26

___________ is an enzyme that clears the clot over a period of ___________

Back 26

Plasmin

Several days

Front 27

What does prothrombin time (PT) assess?

Back 27

Measures integrity of extrinsic pathway (TF)

Factors V, VII, X, prothrombin, fibrinogen

Front 28

Normal range for PT

Back 28

11-13 sec

Front 29

PT is normalized to form _________, which is used to assess ___________

Back 29

INR

Warfarin

Front 30

Normal INR

Back 30

0.8-1.7

2-3 is target for warfarin therapy

Front 31

Activated Partial Thromboplastin Time (aPTT) measures what?

Back 31

Integrity of intrinsic pathway (contact activation)

Factors VIII, IX, XI

Used to monitor unfractionated heparin

Front 32

Normal aPTT

Back 32

30-35sec

Front 33

What does Activated Clotting Time measure?

Back 33

Integrity of intrinsic pathway

Used to monitor high dose heparin

Front 34

Normal ACT

Back 34

90-120 sec

Front 35

What does thrombin time measure?

Back 35

Conversion of fibrinogen to fibrin

Used to screen for abnormal fibrinogen levels

Monitors therapy with fibrinolytic agents

Front 36

What does bleeding time measure

Back 36

Platlet number and function

useful for assessing von Wildebrand disease

Front 37

Normal bleeding time

Back 37

2.0-8.5

>10 abnormal

Front 38

Prolonged bleeding time with normal platlet counts implies what?

Back 38

Impaired platlet function (due to NSAID for example)