Lecture 21: Blood clotting and blood groups Flashcards

1
Q

What is the process of platelet formation called?

What stimulates this?

What is the function of platelet formation?

A

The process of platelet formation is called thrombopoiesis
- process is stimulated by thrombopoietin

Function: Haemostasis and blood clotting/coagulation

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2
Q

How is a platelet plug formed?

A
  1. When tissue is damaged, collage from the sub endothelium is exposed and receptors on the platelets bind to this = aggregation
  2. This causes them to change shape; releasing ADP and thromboxane A2(activation) and the platelets begin to bind to each other = agglutination
    —–> platelet plug
    ADP and thromboxane also stimulates vasoconstriction, which reduces further blood loss
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3
Q

What are the two main clotting pathways ?

How do they differ?

What do both of these pathways result in?

A

INTRINSIC pathway = everything needed in INSIDE the blood

EXTRINSIC pathway = the factors needed are located OUTSIDE the blood

Both pathways result in the activation of factor X which activates prothrombin activator - trigger for stages I & II

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4
Q

What occurs during STAGE I of the clotting cascade?

What is required?

A
  • Construction of blood vessels
  • Formation of platelet plug

The intrinsic & extrinsic pathway activate factor X which activated prothrombin activator - triggers stages I & II

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5
Q

What occurs during STAGE 2 and # of the clotting cascade?

A

STAGE 2 catalyses the formation of thrombin from prothrombin which uses Ca ions as cofactors
prothrombin —————–> thrombin
STAGE 3 catalyses the formation of fibrin from fibrinogen resulting in the formation of a blood clot
FIbrinogen —————-> FIbrin

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6
Q

What factors oppose coagulation?

A
  • To limit aggregation endothelium can excrete:
    Prostacyclin and or nitric oxide
  • To limit blood clotting endothelium can excrete:
    Tissue factor pathway inhibitor - inhibits extrinsic pathway
  • There are a numbers of drugs:
    Warfarin, Aspirin and Heparin
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7
Q

What is the mechanism called which dissolves clots?

How are clots dissolved?

A

= FIBRINOLYSIS
Plasminogen is activated by tissue Plasma Activator t-PA, lysosomal enzymes and Factor VII form plasmin. This hydrolyses fibrin to dissolve the clot

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8
Q

What are the characteristics of Type A red blood cells?

A
  • Antigen A
  • B Antibodies
    = Receives A or O
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9
Q

What are the characteristics of Type B red blood cells?

A
  • Antigen B
  • A antibodies
    = Receives B or O
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10
Q

What are the characteristics of Type AB red blood cells?

A
  • Antigen A and B
  • no antibodies
    = Receives all blood types
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11
Q

What are the characteristics of Type O red blood cells

A
  • Antigen free - neither A nor B
  • A and B antibodies
    = ONLY receives O
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12
Q

D antigen( Rh+) is present in 85% of the population and there are NO preformed antibodies . What are the problems that occur is a Rh- mother receives Rh+ blood from a foetus?

A

If a Rh- patient receives Rh+ blood they will develop anti-Rh antibodies.

  • during childbirth some RBCs from foetus cross the placenta. The mother would then being to synthesis anti-Rh antibodies. The first foetus is unaffected but the second baby is at risk
  • —-> Give mother anti-D antibody at first delivery to prevent antibody development.
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