Haemostasis Flashcards

1
Q

What is haemostasis?

A

The arrest of bleeding in the body

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2
Q

What are the characteristics of the haemostatic system?

A

Permanently ready
Prompt response
Localised response
Protection against unwanted thrombosis

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3
Q

What are the 4 components of the haemostatic system?

A

Platelets
Clotting factors
Fibrinolysis factors
Anti-coagulant defences

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4
Q

What type of cell forms platelets?

A

Megakaryocytes

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5
Q

What is the mean life-span of a platelet?

A

7-10 days

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6
Q

What factor is released by collagen to stimulate a primary response?

A

Von Willebrand Factor

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7
Q

What occurs during primary haemostasis?

A

Endothelial damage exposes collagen
Collagen releases Von Willebrand Factor
These bind to platelets
Platelets then release chemicals such as ADP and Thromboxane A2 which recruit other platelets for aggregation

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8
Q

What is an example of a disease that decreases collagen levels in the endothelium, therefore decreasing the primary response?

A

Scurvy

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9
Q

What is an example of a disease that effects platelets?

A

Thrombocytopenia - a reduced number of platelets, usually caused by bone marrow cancers

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10
Q

What is Von Willebrand’s disease?

A

An inherited disease that leads to a decrease in levels of Von WIllebrands Factor

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11
Q

What is purpura?

A

A fine rash

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12
Q

What is the medical term for a nose bleed?

A

Epistaxis

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13
Q

What is the medical term for heavy menstrual bleeding?

A

Menorrhagia

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14
Q

What are some consequences of failures of the primary haemostatic system?

A

Spontaneous bruising
Purpura
GI bleeding
Conjunctival bleeding
Menorrhagia
Epistaxes
Intracranial haemorrhage
Retinal haemorrhage

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15
Q

What are the 2 pathways of secondary haemostasis?

A

Intrinsic and extrinsic

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16
Q

What occurs in the intrinsic pathway of secondary haemostasis?

A

Calcium from the platelets moves to the cell surface, allowing the negatively charged factors to bind

17
Q

What occurs in the extrinsic pathway of secondary haemostasis?

A

Calcium from the platelets moves to the cell surface, allowing the negatively charged factors to bind

18
Q

What occurs in haemophilia a?

A

There is a deficiency of factor 8

19
Q

What occurs in haemophilia b?

A

There is a deficiency of factor 9

20
Q

What factor converts prothrombin to thrombin?

A

Factor 10a and 5

21
Q

What does thrombin cause?

A

The conversion of fibrinogen to fibrin

22
Q

What are the consequences of failures of secondary haemostasis?

A

Joint and muscle bleeding

23
Q

What occurs in fibrinolysis?

A

Tissue plasminogen activator converts plasminogen to plasmin
Plasmin then breaks down fibrin into D-dimers (Fibrin Degradation Products)

24
Q

What occurs in natural anti-coagulation?

A

Anti-thrombin III is the main natural anti-coagulant
This binds to, and inactivates thrombin
This stops formation of the fibrin complex and factor 8 and 9 activation
Protein C turns off factors 8 and 9
Protein S turns off factors 10 and 5

25
Q

How is a secondary clot regulated?

A

Thrombin binds to thrombomodulin
Thrombomodulin modulates the clot, and can activate protein C and S in the blood, which are an anti-coagulant

26
Q

What are some conditions caused by arterial thrombosis?

A

Myocardial infarction
Cerebrovascular accident (Stroke)
Gangrene

27
Q

What are some conditions caused by venous thrombosis?

A

Deep venous thrombosis
Pulmonary embolism - Occlusion of the lungs caused by an embolus (Unattached thrombus)

28
Q

Wha are some symptoms of arterial thrombosis?

A

Angina - Heart pain caused by hypoxia of cardiac tissue
Claudication - Pain in legs when walking or moving

29
Q

What are some characteristics of an arterial thrombus?

A

Platelet rich and requires anti-platelet agents to treat

30
Q

What are some characteristics of a venous thrombus?

A

Fibrin rich thrombus and requires anti-coagulants to treat

31
Q

What are the 3 points of Virchow’s train of risk factors for venous thrombosis?

A

Stasis - lack of movement
Vessel wall - Valves of the vessel walls degenerate so blood falls back
Hypercoagulability - High levels of blood clotting factors

32
Q

What are some symptoms of Deep Vein Thrombosis (DVT)?

A

Limb feels hot, swollen and tender
Can lead to pitting oedema (Presses in like play-doh and doesn’t move back up)

33
Q

What are some symptoms of pulmonary embolism?

A

Pulmonary infarction
Pleuritic chest pain - inflamed pleural lining rubs on body wall
Collapse
Sudden death
Hypoxia
Right heart strain