Thrombosis

Question 1

What is the purpose of clotting cascade

Answer 1

-makes lot of thrombin
-so that fibrinogen can be converted to fibrin
-fibrin form strands that solidify the agglutinated platelets to prevent blood loss
-produce activated factor X which is a protease that catalyses the conversion of prothrombin to thrombin p

Question 2

How is thrombosis prevented

Answer 2

• anticoagulants
  -endothelial cells have various factors that prevent coagulation
• nitric oxide - inhibited platelets
  *prostaglandin 12- inhibits platelet activation
  *antithrombin-inhibits clotting when bound to heparan

Question 3

What reverses thrombosis

Answer 3

Fibrinolysis ,
Clot is broken down by plasmin which is activated from plasminogen by tPA)

Question 4

What factor activates platelets

Answer 4

Von willebrand ( tissue factor )

Question 5

Arterial thrombosis

Answer 5

• occurs from atheroma rupture or damage to endothelium
  -platelet rich
  -primary
  -may block down stream arteries

Question 6

Venous thrombosis

Answer 6

-results from stasis or hyper coagulant state
-platelet poor
- secondary
-may move to lungs

Question 7

Virchows triad

Answer 7

-stasis - static blood lacks kinetic energy and tends to clot
-hyper coagulant state - eg sepsis
-endothelial damage eg surgery or cannula

Question 8

How is deep vein thrombosis caused

Answer 8

-venous return is blocked
-affected organ becomes congested with fluid
-increased pressure so more filtration

Question 9

Risk of deep vein thrombosis

Answer 9

Thrombosis may become dislodged and make its way back to the heart

Question 10

Different fates of a thrombus

Answer 10

-resolution eg thrombolysis
-embolism - moves to another location and blocks a vessel
-organised -becomes covered by endothelium
-recanalised and organised

Question 11

Explain proximal dvt

Answer 11

-thrombus above the need is more at risk
- can lead to swelling , ulcers,pain
- higher risk of pulmonary embolism

Question 12

Distal DVT

Answer 12

• thrombosis below knee
• less risk
  -rarely cause pulmonary embolism or post thrombotic syndrome

Question 13

Fate of a venous thrombus

Answer 13

• travel back to the right side of the heart if thrombus is dislodged
  -passes through pulmonary circulation
  -causing pulmonary embolism

Question 14

What is pulmonary embolism

Answer 14

Blockage in one of the pulmonary arteries

Question 15

Stages of coagulation

Answer 15

-damage to vessel , exposing subendothelial cells
-von willebrand factor binds to subendothelial cells , activating platelets
-activated platelets release thromboxane a2 & ADP , inducing receptors for fibrinogen
-txa2 and ADP bind to receptors on adjacent platelets and increase expression of glycoprotein complex GPIIb/IIIa
-aggregation- fibrinogens holds platelets together
-fibrinogen is a soluble precursor to fibrin which is insoluble and holds the clot firm
-one clump of platelets aggregate they form a negative charged surface
-exposure of tissue factor, forming TF with coagulation factor vii

Question 16

Why is thrombin important

Answer 16

Cleaves fibrinogen into fibrin

Question 17

How does fibrinogen promote blood clotting

Answer 17

-forming bridges between and activating blood platelets through binding to their GpIIb/IIIa surface membrane fibrinogen receptor

Question 18

Explain extrinsic pathway

Answer 18

-beings In vessel wall
-damaged endothelial cells release tissue factor
-TF combines with calcium on negatively charged platelet surface
Activates factor vii
The viia factor can be inactivated by antithrombin

Question 19

Intrinsic pathway

Answer 19

-begins in blood stream
- activates when blood exposed to collagen and put into charged surface
-

Question 20

What is tissue plasminogen activator

Answer 20

-serine proteases found on endothelial cell s
-catalyse activation of circulating plasminogen into plasmin

Question 21

Role of plasmin

Answer 21

Catalyses breakdown of cross linked fibrin clot into fragments called d dimers

Question 22

How is herapan linked to antithrombin

Answer 22

-expressed by endothelial cells and binds to enzyme inhibitor antithrombin , resulting in AT activation

Question 23

When antithrombin is activated what happens

Answer 23

-inactuves thrombin , factor xa,factor vii,and other components in the clotting cascade