Clotting Flashcards

1
Q

First platelets adhere to the site of injury, how so?

A

Glycoproteins:
Gp 1a/2a + 6 bind directly to exposed collagen
GP 1b bind to vWF, indirectly to collagen
GP 2b/3a bind to Fibrinogen

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2
Q

second thrombosis is activated in the platelets by?

A

Cell surface receptors (ADP, adrenaline, thrombin) activate the conversion of arachidonic acid to Thromboxane 2 by COX

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3
Q

Third, What causes platelets to aggregate?

A

Thromboxane A2

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4
Q

After a platelet plug is formed, we then form a fibrin clot. What causes this?

A

Activation of coagulation Factors by physiological activator e.g. Tissue Factor

These activate eachother in a cascade like dominos

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5
Q

What are the final steps in the coagulation cascade

A

Prothrombin cleaved to Thrombin

Its then cleaves Fibrinogen to Fibrin which forms the clot

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6
Q

What natural Anticoagulants keep us from clotting outside sites of injury?

A

TFPI - switches off clotting factors 7 & 10

Proteins C & S - Switch off 5 & 8

Anti-thrombin - Switches of 5, 8 , 9, 10, 11 & thrombin

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7
Q

What triggers fibrinolysis?

A

Endothelial cells releaseing plasminogen activators (t-PA & u-PA)

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8
Q

What do Tissue Plasminogen Activators do?

A

They cleave plasminogen into plasmin –> breaks down fibrin –> Fibrin Degradation Products

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9
Q

what do we test for in a D-dimer?

A

Fibrin Degradation Products

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10
Q

Anti-thrombotic drugs include antiplatelets and anticoagulants. What types of antiplatelets do we have?

A
  • Target adhering Gylcoproteins (Abciximab)
  • Target surface receptors (Clopidogrel & Ticagrelor)
  • Target Thromboxane 2 production (Aspirin)
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11
Q

Warfarin is a common anti-coagulant what does it do?

A

Reduces conc of various clotting factors inc 2, 7, 9, 10 & prothrombin
works by inhibiting Vit K

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12
Q

Other anti-coagulants include heparins and DOACs, what do DOACs do?

A

Direct Oral AntiCoagulants:

1) Rivaroxaban targets activated factor 10
2) Dabigatran targets thrombin

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13
Q

The clotting cascade starts in two different pathways and becomes the common pathway.
Which factors are involved in each pathway?

A
Intrinsic  = 8, ,9, 11 & 12
Extrinsic = Tissue Factor (TF) & factor 7

They converge on 10

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14
Q

What test measures the function of each of the pathways in the clotting cascade?

A

Prothrombin time (PT) is a test of the extrinsic pathway

activated Partial Thromboplastin Time (aPTT) is a test of the intrinsic pathway

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15
Q

Thrombin is a product of the common pathway of clotting, what effect does it have on the intrinsic/extrinsic pathways?

A

It has a -ve feedback effect on the intrinsic pathway

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16
Q

What effect would Warfarin have on the aPTT & PT

A

could prolong both because it acts on both pathways

17
Q

What effect would aspirin have on the aPTT or PT?

A

None,

Aspiring inhibits COX enzymes preventing aggregation of platelets so it isn’t involved in the clotting cascade