Blood Clotting Flashcards

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1
Q

Coagulation

A

solid blood clot formation to prevent blood loss after damage to the lining of blood vessels

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2
Q

Hemostasis

A

blood is maintained in fluid clot-free state, but ready to clot in response to injury

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3
Q

Clotting process

A
  1. Platelet (Thrombocyte) Aggregation: platelets adhere/aggregate to injured endothelium
  2. Activation of soluble factors: inactive fibrinogen converted to fibrin, fibrin forms a meshwork = solid clot
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4
Q

Blood components

A

45% cells (RBC+WBC+platelets), 55% plasma

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5
Q

Serum

A

liquid left over after clotting

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6
Q

Platelet formation

A

stem cell (in bone marrow) - megakaryoblast - megakaryocyte - breakup of cell as fingers protrude from bone marrow into bloodstream - platelets

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7
Q

Injury to endothelium

A
  1. exposes collagen 2. von Willebrand Factor produced (bridge from platelet to endothelium) These events enable platelet adhesion via platelet receptors
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8
Q

After adhesion, platelets…

A
  1. secrete contents of granules (e.g. ADP, calcium, histamine, serotonin) 2. produce Thromboxane A2 These events amplify the platelet activation response and enable platelet aggregation = primary hemostatic plug
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9
Q

Thromboxane A2

A

stimulates activation of new platelets as well as increases platelet aggregation

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10
Q

Prostacycline

A

secreted by normal endothelium, inhibits platelet aggregation

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11
Q

Thrombopoietin

A

regulates the production of platelets - platelets and megakaryocytes both have receptors

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12
Q

Thrombin

A

converts fibrinogen (soluble) to fibrin (insoluble)

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13
Q

Secondary hemostatic plug

A

fibrin deposition

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14
Q

Clotting Factor activation

A

activates prothrombin to thrombin, via intrinsic or extrinsic pathways (often both)

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15
Q

Intrinsic Pathway

A

initiated by factors within the blood (e.g. activated platelets) or negatively charged surfaces (e.g. glass surface).

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16
Q

Extrinsic Pathway

A

initiated by factors outside the blood (tissue factor from non vascular cells - underlying tissues)

17
Q

Natural Anti-Coagulants

A

(prevent clot from forming) tissue factor pathway inhibitor (TFPI), anti-thrombin III, proteins S and C, thrombomodulin

18
Q

Tissue factor pathway inhibitor (TFPI)

A

produced by endothelial cells. Upregulated by heparin. Inhibits tissue factor+factor VIIa+Ca2+ complex in the extrinsic pathway

19
Q

Anti-thrombin III

A

circulating in the blood in small quantities, binds directly to thrombin. Heparin can promote the action of anti-thrombin III

20
Q

Proteins S and C

A

inactivate factors Va and VIIIa

21
Q

Thrombomodulin

A

binds to thrombin to activate Protein C and deplete thrombin levels. Produced by endothelial cells

22
Q

Fibrinolysis

A

prevents blood clots that occur naturally from growing and causing problems, normal breakdown of clots

23
Q

Plasmin

A

degrades fibrin

24
Q

Plasminogen

A

converted to plasmin by enzymes

25
Q

t-PA

A

tissue plasminogen activator, in endothelium

26
Q

u-PA

A

urokinase-type plasminogen activator, in plasma.

27
Q

PAI

A

plasminogen activator inhibitor

28
Q

_2 -AP

A

_2 antiplasmin (blocks plasmin)

29
Q

Haemophilia:

A

genetic deficiencies in clotting factors e.g. Haemophilia A (Factor VIII deficiency): X-linked - affects males, most common haemophilia

30
Q

Thrombocytopenia

A

(reduced platelet numbers): decreased production of platelets (leukemia, folic acid deficiency), decreased survival of platelets (immunological and non-immunological destruction)

31
Q

Thrombosis

A

inappropriate clot formation cause obstruction of arteries/veins
Arteries - e.g. Atherosclerosis (loss of integrity of endothelium)
Veins - e.g. Deep Vein Thrombosis (stasis - slows blood flow)

32
Q

Disseminated Intravascular Coagulation (DIC)

A

not a primary disease (serious consequence of other diseases), coagulation throughout microcirculation due to expression of tissue factor

33
Q

Atherosclerotic Disease

A

anarterywall thickens as a result of invasion and accumulation ofwhite blood cells due to lipid build up on walls which activates an immune response

34
Q

Anti-coagulant drugs

A

Heparin, Warfarin

35
Q

Heparin

A
  • blocks the action of thrombin by activating the enzyme anti-thrombin III
  • naturally occurring anti-coagulant (mast cells, basophils)
  • sulphated carbohydrate
  • injectable anti-coagulant - heart attacks, DVT
36
Q

Warfarin

A
  • blocks the production of Vitamin K
  • Vitamin K cycles between reduced/oxidised form - blocks reduction of Vitamin K oxide to Vitamin K
  • Vitamin K required for synthesis of clotting factors
  • originally developed as rat poison
  • derivative of coumarin (chemical found in plants)
  • taken orally for treatment of thrombosis
  • many drug-drug interactions can affect activity