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Cardiorespiratory 2 > Haemostasis and Inherited bleeding disorders > Flashcards

Haemostasis and Inherited bleeding disorders Flashcards

1
Q

what are the key components of haemostasis

A
  • Platelets
  • Von Willebrand factor
  • Clotting proteins
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2
Q

what makes up primary haemostasis

A
  • platelets and VWF dependent
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3
Q

what makes up secondary haemostasis

A
  • fibrin
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4
Q

where are platelets derived from

A
  • Non nucleated cytoplasmic fragments derived from bone marrow megakaryocytes
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5
Q

What is the structure of platelets

A
  • 1-4um
  • Cellular membrane is made out of lipid bilayer, cell membrane, and glcyorpotein receptors
  • Lipid bilayer with underlying microtubular system – series of granules
  • Multiple components in each granule – dense granule important agonists, alpha granules fibrinogen, FV, P selectin
  • Platelet membrane – complex of at least 9 glycoproteins.
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6
Q

what is the average amount of platelets in the blood

A
  • Reference range for platelets in blood 140 to 400-450x109/
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7
Q

what is the lifespan of a platelet

A
  • 8 to 14 days
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8
Q

what system removes platelets from the blood

A
  • Removed from the circulation by the reticuloendothelial system
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9
Q

describe what the cell membrane of a platelet it like

A
  • glycoproteins molecules have receptors for agonist, adhesive, coagulation factors and other platelets
  • the receptors that are most abundant are GPIIb/IIIa and Gp1b
  • the cell membrane also contains phospholipids
  • it is associated with prostaglandin synthesis, calcium mobilisation, localisation of coagulant activity to the platelet surface
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10
Q

what are the organelles in a platelet

A
  • there are platelet specific granules such as
  • dense osmophilic granules (dense bodies, d-granules)
  • a granules are the glue that hold the platelets together
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11
Q

what are the substances that can be in a-granules

A
  • VWF
  • platelet factor 4
  • b-thromboglobulin,
  • thrombospondin,
    factor V,
    fibrinogen,
    fibronectin,
    platelet derived growth factor
    high molecular weight
    kininogen,
    tissue plasminogen activator inhibitor-1
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12
Q

where is VWF found

A
  • VWF from plasma or from granules
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13
Q

How does VWF react when it attaches to collagen

A
  • Collagen exposed and the nature of the collagen allows the VWF to bind to it
  • VWF binds to GPIb – intitial monolayer of platelets – subsequent activation, via a G-protein mechanism(facilitated by agonist relese ) – Shape change – disc to sphere – pseudopods – complex of Gpib IX, IIbIIIa, VWF, fibrinogen.
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14
Q

what are the agonist for VWF

A

– collagen, ADP, thrombin, adrenaline, serotnonin AA metabolites – TXA2

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15
Q

what acid does VWF release when it binds to IIb

A

arachidonic acid

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16
Q

describes what happens to the arachidonic acid released when VWF binds to IIb

A
  • Arachidonic acid is released converted to by lipo-oxygenase enzymes to leucotrienes – chemoattractants to white cells, remaining Arachidonic Acid converted by cyclooxygenase and then TXA synthetase into Thrombocxane.
  • Thromboxane causes further granule release and local vasoconstriction and further local aggregation – exerts this by intracellular calcium shifts.
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17
Q

what is another pathway by which VWF carries out its role

A
  • 2nd pathway of activation by agonists interaction on membrane surface receptors and G protein activation of phopholipase C. – further calcium release – stimulate contractile system – liberation of Arachidonic Acid and further generation of TXA2
  • Flip fop of membrane charge – negative charged moieties onto outer surface – procoagulant
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18
Q

name some serious inherited platelet disorders

A
  • Lack GpIb – Bernard Soulier syndrome – have thrombocytopenia as well
  • Lack GpIIb/IIIa – Glanzmann’s – all the clotting tests look normal except the fact that the platlets don’t work
  • Likely to need platelets or Novoseven medication that is a turbo boost to the clotting system that try’s to get some thrombin activity
19
Q

what is the disorder called when you lack Gp1b

A

– Bernard Soulier syndrome

20
Q

What is the disorder called when you lack GpIIb/IIIa

A

Glanzmann’s – all the clotting tests look normal except the fact that the platlets don’t work

21
Q

what are the less serious platelet conditions

A
  • Storage pool disorders

* Weak agonist response defects

22
Q

what is the most common inherited blood clotting disorder

A

von willebrand disease

23
Q

what is the genetics of VW disease

A

• Autosomal inheritance – girls & boys

24
Q

what are the types of VW disease

A
  • Type 1 – mild to moderate deficiency
  • Type 2 – protein present but defective
  • Type 3 – total absent protein
25
Q

how do you treat von willebrand disease

A
  • treat with DDAVP
  • tranexamic acid
  • VWF containing concentrate
26
Q

How is tissue factor III activated

A
  • it is present on sub endothelial tissue
  • expressed by cells which are normally not exposed to flowing blood
  • physical injury exposes tissue factor to flowing blood
  • necessary for the initiation of coagulation via factor VII
27
Q

what pathways do APPT test

A

intrinsic and common

28
Q

what pathways do PT test

A

extrinsic and common

29
Q

what factors does thrombin activate

A

V to Va
VIII to VIIIa
XI to XIa

30
Q

what inactivates the tissue factor

A

Tissue factor pathway inhibitor is an antagonist to the tissue factor at the start and starts to slow the whole process, then it ultimately turns it off

31
Q

describe the factors of haemophilia A

A
  • Deficiency of IXa
  • Cannot amplify
  • They clot a little bit and then it breaks away
32
Q

describe the factors of haemophilia b

A
  • deficiency of VIII
33
Q

what are the symptoms of haemophilia

A 
Bleeds
Soft tissue
Joints (knees, ankles, elbows)
Psoas
Intracranial bleeds 
Operative sites
34
Q

how do you prevent the onset of haemophilia symptoms

A

Learn to self administer factor concentrate

Moderate fVIII levels

35
Q

what does prophylaxis mean

A

how to prevent something

36
Q

what is used to treat mild haemophilia a

A

DDAVP

37
Q

what does antithrombin inhibit

A

major inhibitor of thrombin and Xa

• also inhibits VII, IX, XI

38
Q

what protein family is antithrombin a part of

A

• Member of the SERine Protease INhibitor family

39
Q

what increases the action of antithrombin

A
  • Inhibitory activity increased 5 -10,000 fold in the presence of heparin
  • Physiologically binds to heparan sulphate on the surface of the vascular endothelium
40
Q

what are the vitamin K dependent glycoproteins synthesised in the liver

A

Protein C and Protein S

41
Q

how is protein C activated

A
  • it is activate by thrombin

- the activation is increased 20,000 fold with thrombomodulin

42
Q

what does activated protein C do

A
  • serine protease
  • inactivates Va and VIIIa
  • Protein S
  • cofactor for Activated Protein C (APC)
43
Q

what do protein C and S do

A

proteins C and S help adjust the rate of blood clot formation.

Cardiorespiratory 2 (43 decks)

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