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YEAR 5: Haematology > Haem: Coagulation Pt.1 > Flashcards

Haem: Coagulation Pt.1 Flashcards

1
Q

List some pro-coagulant factors in the body.

A
  • Platelets
  • Endothelium
  • vWF
  • Coagulation cascade
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2
Q

List some anti-coagulant factors in the body.

A
  • Fibrinolysis
  • Anti-thrombins
  • Protein C/S
  • Tissue factor pathway inhibitor
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3
Q

Which three responses are stimulated by vessel injury?

A
  1. Vasoconstriction
  2. Platelet activation (forms primary haemostatic plug)
  3. Activation of the coagulation cascade
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4
Q

What are the components of blood clot formation?

A
  • Vascular endothelium
  • Platelets
  • Coagulation factors
  • White blood cells
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5
Q

What are the two main functions of the endothelium?

A
  • Synthesis of prostacyclin, vWF, plasminogen activators and thrombomodulin
  • Maintain barrier between blood and pro-coagulant subendothelial structures
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6
Q

How many platelets are produced by each megakaryocyte?

A

4000

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7
Q

What is the life span of platelets?

A

10 days

NOTE: this is important because it means that the effect of antiplatelet drugs lasts for 10 days after stopping the drug

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8
Q

What are glycoproteins?

A

Cell surface proteins through which platelets can interact with the endothelium, vWF and other platelets

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9
Q

What do dense granules contain?

A

Energy stores (ATP and ADP)

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10
Q

Which features of platelets enable them to massively expan their surface area?

A

Open cannalicular system and microtubules and actomyosin

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11
Q

What are the two ways in which platelets can adhere to sub-endothelial structures?

A

DIRECTLY - via GlpIa

INDIRECTLY - via binding of GlpIb to vWF (this is MORE IMPORTANT)

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12
Q

which factors, released by platelets after adhesion, promote platelet aggregation?

A

ADP

Thromboxane A2

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13
Q

How do platelets bind to each other?

A

GlpIIb/IIIa

It also binds to fibrinogen via this receptor

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14
Q

Describe the effects of aspirin and other NSAIDs on the arachidonic acid pathway.

A

Aspirin is an irreversible COX inhibitor

Other NSAIDs reversibly inhibit COX

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15
Q

What is the rate-limiting step for fibrin formation?

A

Factor 10a

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16
Q

What are the effects of thrombin formation?

A
  1. Activates fibrinogen (converts it to fibrin)
  2. Activates platelets
  3. Activates profactors (factor 5 and 8)
  4. Activates zymogens (factor 7, 11 and 13)
17
Q

Name the complex that is responsible for activating prothrombin to thrombin.

A

Prothrombinase complex

18
Q

Outline the initiation phase of the clotting cascade.

A
  • Damage to the endothelium results in exposure of tissue factor which binds to factor 7 and activates it to factor 7a
  • The tissue factor-factor 7a complex then activates factors 9 and 10
  • Factor 10a binds to factor 5a resulting in the first step of the coagulation cascade
19
Q

Outline the amplification phase of the clotting cascade.

A
  • Activated factors 5 and 10 will result in the production of a small amount of thrombin
  • This thrombin will activate platelets
  • Thrombin will also activate factor 11 which activates factor 9
  • Thrombin also activates factor 8 and recruits more factor 5a
  • Factors 5a, 8a and 9a will bind to the activated platelet
20
Q

Outline the propagation phase of the clotting cascade.

A
  • Activated factors 5, 8 and 9 will recruit factor 10a
  • This results in the generation of a large amount of thrombin (thrombin burst)
  • This enables the formation of a stable fibrin clot
21
Q

Describe the extrinsic pathway

A
  • Tissue activation: Damaged endothelium exposes TF
  • SEVEN: VII + TF > TF-VIIa complex > activates X
  • FIVE: Va + Xa > prothrombinase complex
22
Q

How is the extrinsic pathway monitored?

A

Prothrombin time (PT)
The time in seconds that it takes plasma to clot after the addition of phospholipid, tissue factor (factor III), and calcium to the specimen

  • Monitor warfarin therapy (INR)
23
Q

Describe the intrinsic pathway

A
  • Surface activation: Exposed collagen
  • TWELVE: XII > XIIa
  • ELEVEN: XI > XIa
  • NINE: IX > IXa
  • EIGHT: VIIIa complexes with IXa (tenase complex)
  • TEN: X > Xa
24
Q

How is the intrinsic pathway monitored?

A

Activated partial thromboplastin time (APTT)
The time in seconds that it takes plasma to clot after the addition of a contact agent that fully activates factors XII along with calcium and phospholipids

  • Monitor heparin therapy
25
Q

Describe the common final pathway

A
  • FIVE: Va + Xa > prothrombinase complex
  • Converts prothrombin to thrombin
  • Thrombin cleaves fibrinogen to fibrin
  • Forms stable fibrin clot

YEAR 5: Haematology (37 decks)

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