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509 - Cellular and Transfusion Science > Disorders of homeostasis > Flashcards

Disorders of homeostasis Flashcards

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1
Q

What does healthy endothelium express which blocks platelet adhesion?

A

ecto-ADPase (CD39)
prostacyclin (PGI²)
nitric oxide (NO)

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2
Q

How are platelet disorders organised?

A

Acquired (drugs etc)
Qualitative (functional defect, inherited/acquired)
Quantitative (thrombocytopenia or thrombocytosis)

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3
Q

Outline thrombocytopenia

A
  • Deficiency of platelets in blood
  • Mild = 50-150
  • Moderate = 20-50
  • Severe = <20
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4
Q

What is a normal platelet count?

A

150-359 x10⁹/L

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5
Q

What is thrombotic microangiopathies?

A

A pattern of damage that can occur inside the smallest blood vessels in vital organs, often kidney or brain

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6
Q

Very briefly outline haemostasis

A

Results in platelet plug formation
Does NOT involve coagulation pathways
Includes disorders of platelet numbers/size/functionality

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7
Q

Briefly outline secondary homeostasis

A

Formation of an insoluble fibrin clot after coagulation cascade
Fibrinolysis occurS
Common, Intrinsic, and extrinsic pathways

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8
Q

Which pathway is the main initiation for coagulation?

A

Extrinsic

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9
Q

Outline the extrinsic pathway

A

Exposure of transmembrane receptor tissue factor (TF) to plasma factor VII, activating factor X.

Prothrombinase complex activates thrombin (from prothrombin), activating FXI

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10
Q

Outline the intrinsic pathway

A

Amplifies the coagulation cascade
Tenase complex amplifies activation of FX, large amount of thrombin generated.

Thrombin cleaves fibrinogen to form soluble fibrin monomers, which polymerise to form a polymer.

Thrombin activates FXII to cross link calcium (stabilises polymer)

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11
Q

what does a deficiency of protein C or S lead to?

A

Thrombin spread into vasculature due to prevention of cleavage and inactivation of FV

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12
Q

What happens after an injury is healed?

A

Plasminogen begins to dissolve the fibrin clot.

Plasmin cleaves the network and releases FDP, and cleaves fibrinogen. It also inactivates Fva and FVIIa

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13
Q

State two fibrinolysis defects

A

Hyperfibrinolysis (bleeding snd thrombosis)
Hypofibrinolysis (thromboembolic disease associations)

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14
Q

What are the inhibitors in coagulation?

A

TFPI, Antithrombin, Protein C, Thrombomodulin

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15
Q

What are the intrinsic and extrinsic tenases?

A

Extrinsic = TF-VIIa
Intrinsic = IXa VIIIa

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16
Q

What does a congenital deficit of factor VIII cause?

A

Haemophilia A

17
Q

What does a deficiency of combined FV and FVIII cause?

A

Rare autosomal recessive bleeding disorder. Normally due to a mutation in transport protein.

Treat sith FVIII concentrate.

18
Q

What does a deficiency of factor IX lead to?

A

Haemophilia B

19
Q

What does a deficiency in factor XI lead to?

A

Haemophilia C
3 mutations, majority type II or III

20
Q

Which factors can become an acquired deficiency?

A

Factor II - antibody due to lupus
Factor V - after surgery/transfusion
Factor VII - very rare
Factor IX - rare, associated with postpartum
Factor X - amyloidosis

21
Q

How does liver disease affect haemostasis?

A

Increased prothrombin time due to a decrease of extrinsic coagulation factors synthesized in the liver

22
Q

What else can increase prothrombin time?

A

Vitamin K deficiency (due to vit k dependant factors)

23
Q

What is prothrombin time?

A

A measure of efficiency of the extrinsic clotting system

24
Q

What is activated partial thromboplastin time?

A

Same as PT but with an added activator to speed the process up, resulting in a narrower reference range

25
Q

What agents are used in anticoagulant therapy?

A

Aspirin (platelet function inhibition)
Warfarin (for vit. K dependant factors)
Heparin (inhibits thrombin)
Thrombin inhibitors
FXa inhibitors
Thrombolytic agents (e.g., streptokinase)
Natural coagulation inhibitors

26
Q

Which factors are vitamin K dependent?

A
  • FII
  • FVII
  • FIX
  • FX
  • Protein C
  • Protein S
27
Q

What is international normalised ratio?

A

A blood test telling you how long it takes for you blood to clot.

Calculated by: INR = PR*(ISI)

PR = prothrombin rate
ISI = international sensitivity index

509 - Cellular and Transfusion Science (15 decks)

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