Coagulation

Question 1

Plasminogen can be proteolytically activated to _________ .

Answer 1

Plasmin

Question 2

Which form of this protein, plasminogen or plasmin, is freely circulating when you are NOT clotting?

Answer 2

Plasminogen

Question 3

Which form of this protein is the active, protein plug (clot) forming form? Fibrinogen or fibrin

Answer 3

Fibrin. Aggregates to form a fiber plug.

Question 4

What kicks off the clotting cascade?

Answer 4

Cells that do not normally come into contact with RBC and other blood products, now come into contact with these and release signals to alert other cells that there is a problem. Signals for vasoconstriction and clotting.

Question 5

What is the role of TXs in mitigating bleeding?

Answer 5

Assist platelet aggregation

Question 6

How does our body prevent coagulation downstream of original injury to the endothelium?

Answer 6

The endothelial cells downstream of the cut display anti-coag proteins, bind anti-coag proteins, and destroy the accelerators of the coagulation reaction.
Endothelial cells also produce Prostacyclins that dilate vessels downstream to inhibit platelet aggregation.

Question 7

Thrombin plays an important role in forming a platelet plug and in activating the enzyme Factor XIIIa (fibrin stapler) to _________ fibrin.

Answer 7

Cross-link

Question 8

Does Thrombin activate platelets

Answer 8

Yes

Question 9

What protein is responsible for making Fibrinogen insoluble so that its active form, Fibrin, will begin to polymerize?

Answer 9

Thrombin

Question 10

What protein cross-links Fibrin, making it a rigid & strong mesh for helping platelets form clots to plug holes in endothelium?

Answer 10

Factor XIIIa

Question 11

What protein activates Factor XIII to Factor XIIIa?

Answer 11

Thrombin

Question 12

What protein activates platelets to change surface receptors and initiate shape change?

Answer 12

Thrombin

Question 13

Upon injury, subendothelial cells at the site of injury release _________ that binds to Factor VIIa.

Answer 13

Tissue Factor

Question 14

When the Tissue factor/Factor VIIa complex binds to Factor X, Factor X is activated forming Factor Xa which then activates small quantities of _________ .

Answer 14

Thrombin

Question 15

Factors XI, V and VIII have a +ive feedback loop that increases the activation of ___________ x10,000

Answer 15

Prothrombin

Question 16

The complex of Factors _____ & _______ activate Prothrombin to Thrombin x10,000 faster than Xa alone.

Answer 16

Xa & Va

Question 17

Accelerators of coagulation are found on the cell surface of _________ .

Answer 17

Platelets

Question 18

List the 3 steps in clot formation and maintenance

Answer 18

1. Initiation
2. Amplification
3. Propagation & Stabilization

Question 19

What keeps the clot localized, preventing clots from over-propagating or causing emboli?

Answer 19

1. Limiting initiation: LACI (lipoprotein associated coag factor)
2. Limit amplification: anti-thrombin/heparin
3. Limit propagation: protein C-S destroys accelerators
4. Dissolve/digest clots with plasmin

Question 20

LACI does what to limit initiation of clot formation?

Answer 20

inactivates TF-VIIa-Xa to limit and terminate initiation

Question 21

What keeps the coag localized?

Answer 21

Platelet adhesion to the site

Question 22

What is the action of Antithrombin III in limiting amplification of clotting?

Answer 22

inactivates Thrombin, Factor Xa and IXa if they flow away from the injured site

Question 23

Plasmin digests clots by digesting which protein aggregate?

Answer 23

Fibrin

Question 24

Plasmin is activated by activated protein ____ and ________ _________ .

Answer 24

Protein C; plasminogen activator

Question 25

Endothelial cells express ____________ , a transmembrane protein that binds to thrombin and protein C. Activated C-S complexes inactivate the coag amplifiers Va and VIIIa.

Answer 25

thrombomodulin

Question 26

What protein and proteoglycan bind to Thrombin, Xa and IXa, inactivating them?

Answer 26

Anti-thrombin III & Heparin

Question 27

What protein inhibits the Tissue Factor-VIIa complex from activating factor Xa?

Answer 27

LACI

Question 28

What complex on endothelial cell surfaces binds Factors Va and VIIIa and digests them as well as releasing plasmin to digest the clot?

Answer 28

C-S complex. (proteins C & S)

Question 29

Do all the protein-protein interactions occur freely in the plasma?

Answer 29

No, they all occur on the extracellular surface of subendothelial cells, endothelial cells or platelets.