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Cell Biology > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

What is the average blood volume?

A

4-6 litres

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2
Q

What is the name given to when you lose more than 20% of your blood?

A

Hypovolaemic shock

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3
Q

Define haemostasis

A

The cessation of blood loss from damaged vessels

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4
Q

What does haemostasis require?

A

Cell-cell communication

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5
Q

How many cells per mm3 of peripheral blood do Erythrocytes make up?

A

5 million cells per cm^3

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6
Q

What is the lifespan of an erythrocyte? What is the significance that they are anucleate when they are damaged?

A
  • 120 days

- They cannot repair themselves as they have no nucleus for transcription

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7
Q

What are the 3 phases of haemostasis?

A
  1. Vascular phase
  2. Platelet phase
  3. Coagulation phase
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8
Q

What occurs during the vascular phase?

A

Vasoconstriction
Endothelial cells contract
Endothelial adhesion increases

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9
Q

In the vascular phase of haemostasis, what does the contraction of endothelial cells result in?

A
  • Exposes basal lamina to blood

- Releases factors; ADP, tissue factor, endothelins

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10
Q

In the vascular phase of haemostasis, what does the release of ADP result in?

A

ADP - platelet aggregation

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11
Q

What are endothelins?

A

Peptide hormones which stimulate contraction of smooth muscle and promote mitosis of damaged tissue in vessels

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12
Q

During the vascular phase of Haemostasis, what are 4 examples of factors that endothelial cells release? What do each of these factors contribute to?

A
  1. ADP - platelet aggregation
  2. Prostacyclin - reduces spread of platelet aggregation 3. Tissue Factor - involved in extrinsic pathway of coagulation
  3. Endothelins - stimulate contraction of smooth muscle
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13
Q

In smaller vessels how can endothelial adhesion help haemostasis?

A
  • Endothelial cells can stick together to cover damaged vessels
  • Can also provide attachments for platelets
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14
Q

How and where are platelets formed? How long is the life span of a platelet?

A
  • Megakaryocytes have structures that project into marrow sinuses in the bone marrow - These pockets of cytoplasm them pinch off to form platelets -
    Life span of a platelet is 10 days
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15
Q

What are the 3 stages of the platelet phase?

A
  1. Adhesion
  2. Activation
  3. Aggregation
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16
Q

What is the platelet phase dependent on?

A

Temperature

17
Q

During platelet adhesion, what do the platelets adhere to? What factor is important for this?

A
  • They adhere to the endothelium and basal lamina

- von Willebrand factor (for activation and aggregation of platelets)

18
Q

What occurs during the activation stage in the platelet phase?

A
  • They swell and form spike extensions

- Granulolysis

19
Q

During platelet activation, what are 5 examples of substances released by granulolysis? What do they each do?

A
  1. ADP - platelet aggregation
  2. Serotonin - stimulates smooth muscle contraction
  3. Thrombaxane A2 - stimulates smooth muscle contraction
  4. Clotting factors - promote clot formation
  5. Ca2+ - platelet aggregation and coagulation
20
Q

What is the aggregation stage of the platelet phase stimulated by?

A

ADP, thromboxane A2 and calcium ions

21
Q

What are 3 examples of substances that inhibit platelet activation?

A
  1. Prostacyclin
  2. Nitrous Oxide (produced by intact endothelial cells)
  3. Aspirin
22
Q

What does prostacyclin do?

A

Inhibit platelet activation and vasodilator

23
Q

What are the 2 pathways involved in the coagulation phase of haemostasis?

A
  1. Intrinsic Pathway

2. Extrinsic Pathway

24
Q

Which vitamin is essential for formation of clotting factors in the liver?

A

Vitamin K

25
Q

What is essential for the formation of clotting factors in the liver?

A

Vitamin K

26
Q

As well as catalysing the conversion of fibrinogen into fibrin, what is another function of thrombin?

A

It causes release of more tissue factor and clotting factors

27
Q

Why is clot restriction important?

A

Prevents the formation of a thrombus

28
Q

What are 3 substances that inhibit coagulation?

A
  1. Thrombin stimulates anti-thrombin III to slow down coagulation
  2. Natural anticoagulants e.g. heparin and prostacyclin
  3. Thrombolytics e.g. warfarin and aspirin
29
Q

Describe the pathway for fibrinolysis of a clot

A

Clot removal by plasmin
Plasminogen activated by thrombin and t-PA (tissue plasminogen activator)
Plasminogen is converted to plasmin which digests the fibrin strands in the clot

30
Q

Give 4 examples of disorders related to abnormal haemostasis

A
  • Haemophilia
  • Deep vein thrombosis
  • Liver function
  • von Willebrand’s disease
31
Q

What are the 3 types of haemophilia? What clotting factors are absent in each type?

A
  • A - factor VIII, X-linked recessive
  • B - factor IV, X-linked recessive
  • C, factor VI, autosomal recessive
32
Q

Haemophilia B is associated with which clotting factor?

A

Factor IV

33
Q

Clotting factor VIII is associated with which type of haemophilia?

A

Haemophlia A

34
Q

Clotting factor VI is associated with which type of haemophilia?

A

Haemophilia C

35
Q

What kind of disease is acquired haemophilia?

A

An autoimmune disease

36
Q

What is the cause of deep vein thrombosis?

A

Clotting factor accumulation

37
Q

What is von Willebrand’s disease?

A

vWF deficiency

vWF factor links platelets to endothelium by activating and aggregating them

Cell Biology (21 decks)

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