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CSP1 > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

What are the 3 key components to haemostasis?

A
  • platelets
  • VWF
  • clotting proteins
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2
Q

Define haemostasis

A

Bleeding through a lesion/defect in the vascular wall

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3
Q

What is primary haemostasis?

A
  • platelets adhere to the margins of the lesion

- platelets aggregate forming a primary platelet plug

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4
Q

What are the properties of platelets?

A
  • non-nucleated
  • derived from bone marrow megakaryocytes
  • 1 to 4 micrometer diameter
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5
Q

What is the normal volume of platelets in blood?

A

140 to 400-450 x 10^9 L

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6
Q

What is the lifespan of platelets?

A

8-14 days

Then removed from circulation by reticuloendothelial system

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7
Q

What are the features of the platelet cell membrane?

A
  • glycoproteins

- phospholipids

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8
Q

What is the role of glycoproteins in the platelet cell membrane?

A
  • receptors for agonists, adhesive proteins, coagulation factors, other platelets
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9
Q

What are the most abundant glycoproteins in the platelet cell membrane?

A
  • GpIIb/IIIa

- GPIb

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10
Q

What is the role of the phospholipids in the platelet cell membrane?

A
  • prostaglandin synthesis
  • calcium mobilisation
  • localisation of coagulant activity to platelet surface
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11
Q

What organelles do platelets contain?

A
  • dense osmophillic granules (nucleotides - ADP)

- alpha granules (series of different proteins)

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12
Q

What is the role of VWF?

A
  • forms a bridge linking the exposed collagen and platelet

- also directly links 2 platelets

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13
Q

Serious inherited platelet disorder where you lack Gp1b?

A

Bernard Soulier Syndrome

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14
Q

Serious inherited platelet disorder where you lack GpIIb/IIIa?

A

Glanzmann’s

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15
Q

What is the treatment for Bernard Soulier and Glanzmann’s?

A

Platelets or novoseven

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16
Q

Steps of initial adhesion?

A
  • vessel wall injury
  • platelets contact with and adhere to collagen and subendothelial bound VWF via GpIb
  • Gp IIb/IIIa exposed
  • forms second binding site for VWF so fibrinogen can bind promoting platelet aggregation
17
Q

Features of VWD

A
  • autosomal inheritance
  • deficient or defective VWF
  • type 1 = mild to moderate deficiency
  • type 2 = protein present but defective
  • type 3 = total absent protein
  • treat with DDAVP if mild
  • also treat with tranexamic acid and VWF containing concentrate
18
Q

What is TF?

A
  • present on subendothelial tissue
  • expressed by cells which are normally not exposed to flowing blood
  • physical injury exposes TF to flowing blood
  • necessary for coagulation initiation
  • forms via factor VII
19
Q

Steps of secondary haemostasis

A
  • TF activates coagulation factors in blood at site of injury
  • coagulation factors adhere to platelet surfaces and form catalytic complexes
  • complexes cause formation of thrombin
  • thrombin converts fibrinogen to fibrin
  • fibrin polymers form long chains between platelets in the platelet plug, cross linked, form stable clot
20
Q

Difference between haemophilia A and B

A 
A = fVIII deficiency
B = fix deficiency
21
Q

Differences between severe, moderate and mild haemophillia

A

Severe < 1%
Moderate 2-5%
Mild 5-40%
(severe bleed spontaneously and potentially fatal)

22
Q

Sites of severe haemophilia

A 
Soft tissue
Joints (knees, ankles, elbows)
Psoas
Intracranial
Operative sites
23
Q

Prophylaxis for severe haemophillia

A
  • self administer factor concentrate

- moderate fVIII levels

24
Q

Treatment for mild and moderate haemophilia

A 
Mild A = DDAVP
Factor concentrate (often can't self admin)
25
Q

What is antithrombin?

A
  • major inhibitor of thrombin and Xa
  • also inhibits VII, IX, XI
  • member of the SERine Protease INhibitor family
26
Q

What is protein C?

A
  • activated by thrombin
  • activation increased with thrombomodulin
  • inactivates Va and VIIIa
  • is a serine protease
27
Q

What is protein S?

A
  • cofactor for activated protein C
28
Q

Fibrinolytic Pathway

A

Plasminogen breaks down into plasmin by tPA, plasmin convers fibrin into fibrin degradation products which are soluble

CSP1 (20 decks)

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