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Flashcards in Hemostasis Deck (72)
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1
Q

Define Hemostasis

A

The physiological processes that stop bleeding

2
Q

What are the four steps that constrain bleeding?

A
  1. Physical factors
  2. Platelets form hemostatic plug
  3. Coagulation due to production of fibrin clot
  4. Clot retraction
3
Q

What are the two physical factors that slow bleeding?

A
  1. Back Pressure

2. Vasoconstriction

4
Q

Why do black eyes form?

A

Bleeding below eye not easily stopped

5
Q

What chemicals contribute to vasoconstriction?

A

Serotonin
Epinephrine
Thromboxane A2

6
Q

What does thromboxane do?

A
  1. Vasoconstriction

2. Platelet aggregation

7
Q

What reduces uterine blood loss after birth?

A

Compression of blood vessels due to underlying muscles

8
Q

Where is thrombopoietin produced?

A

Liver and Kidney

9
Q

The release of platelets from bone marrow is induced by _____

A

thrombopoietin

10
Q

What is the von Willebrand factor?

A

Glycoprotein that:

  1. Forms bridge between platelet surface receptors and collagen
  2. Important in platelet adhesion to wound sites
  3. Not an enzyme
11
Q

What is the von Willebrand factor produced by?

A

Endothelial cells due to adherence of platelets

12
Q

What other protein does the von Willebrand factor bind to?

A

Factor VIII

13
Q

What activates thrombin?

A

Membrane phospholipids

14
Q

What initiates a cascade that ends in clot formation?

A

thrombin activation

15
Q

What induces factor VIII to dissociate from von Willebrand factor?

A

thrombin activation

16
Q

Is von Willebrand factor bound to Factor VIII in normal circulation or during clot formation?

A

normal circulation

17
Q

What does the released of ADP from ruptured cells cause?

A

Platelet aggregation

18
Q

When ADP binds to platelet ADP receptors, what is released?

A

thrombin

19
Q

Drugs such as _____ irreversibly inhibit the platelet ADP receptor?

A

Plavix

20
Q

fibrin stabilizing factor is also known as _______

A

Factor XIII

21
Q

During coagulation, thrombin cleaves ______ into ______ that assemble into ordered arrays of _____

A

Thrombin cleaves fibrinogen into fibrin monomers which assemble into fibrous arrays of fibrin

22
Q

What does Factor XIII do?

A

Stabilizes and tightens polymerized fibrin by forming covalent bonds between fibrin strands

23
Q

What replaces unstable platelet aggregates during coagulation?

A

Factor XIII

24
Q

Coagulation factors are _____

A

serine proteases

25
Q

The intrinsic pathway of the coagulation cascade is initiated by

A

factor XII

26
Q

Does a lack of Factors XII lead to bleeding disorders?

A

Hell no. We don’t need no Factor XII

27
Q

The extrinsic pathway of the coagulation cascade is initiated by released of ______

A

tissue factor:

Factor III, thromboplastin

28
Q

What is tissue factor produced by?

A

Subendothelial tissues:
smooth muscle cells
Neutrophils
Monocytes

29
Q

Endothelial cells produce tissue factor in response to _______

A

inflammatory mediators

30
Q

What three main conversions take place during the final common pathway of the coagulation cascade?

A
  1. Conversion of inactive factors X to its active form (Xa)
  2. Conversion of prothrombin to thrombin
  3. Conversion of fibrinogen to fibrin
31
Q

What is purpura?

A

Red/purple discolorations of skin that do not blanch with pressure

32
Q

Prothrombrin time (PT) is a coagulation test of the ______ system

A

extrinsic

33
Q

What does the Prothrombin time test measure

A

How long plasma takes to clot after mixed with tissue factor and CaCl2

34
Q

What time defines a failed PT test?

A

more than 11 seconds

35
Q

The PT test measures effectiveness of __________ drugs

A

coumarin-type anticoagulant drugs (Coumadin-Warfarin)

36
Q

What do coumarin-type anticoagulant drugs do?

A

Inhibit vitamin K-dependent synthesis of prothrombin and factors VII, IX, and X

37
Q

What is a coagulation test of the intrinsic system?

A

Activated partial thromboplastin time (aPTT)

38
Q

What does the Activated Partial Thromboplastin Time test measure?

A

clotting time from activation of factor XII through the formation of fibrin clot

39
Q

What is a normal aPTT test time?

A

25 - 38 seconds

40
Q

What is the aPTT test used for?

A

monitor heparin therapy

41
Q

What does Heparin bind to in heparin therapy?

A

enzyme inhibitor antithrombin

42
Q

Hypocoagulation is the word for ________ disorders

A

bleeding disorders

43
Q

Hypercoagulation is the word for ______ disorders

A

thrombin disorders

44
Q

Thrombocytopenia is characterized by _____

A

low platelet number

45
Q

What is thrombocytopenia thought to be caused by?

A

autoimmune disease

“idiopathic thrombocytopenia purpura”

46
Q

What is Von Willebrand disease?

A

reduced von Willebrand factor

47
Q

What is the most common hereditary coagulation abnormality in humans?

A

Von willebrand disease

48
Q

What is Hemophilia?

A

Lack of factors VIII or IX

49
Q

Most Hemophilia is inherited in what way?

A

X-linked recessive

50
Q

Vitamin K is required for ______ production by the liver

A

coagulation factor production

51
Q

Hypercoagulation can lead to _____ which can lead to _____

A

Hypercoagulation ->
Intravascular clot formation ->
Stroke

52
Q

What is a regulatory protein that functions as an anti-coagulant?

A

Protein S

53
Q

In the gene therapy drug study, a single intravenous injection of __________ that expresses _______ improved the bleeding phenotype in all six patients

A

injection of adenovirus-assocatied virus (AAV) ->

expresses factor IX

54
Q

________ disease was successfully treated by AAV injection in six patients

A

hemophilia B

55
Q

Retraction occurs within ____ to ____ of clot formation

A

minutes or hours

56
Q

What does clot retraction do?

A

Stabilizes inured site by pulling torn edges o vessels closer together

57
Q

Clot retraction requires ______

A

platelet actin and myosin filament

58
Q

Dissolution is also known as _____

A

fibrinolysis

59
Q

Dissolution is mainly a function of ______

A

plasmin

60
Q

Plasmin circulates as inactive ______

A

proenzyme plasminogen

61
Q

How is plasminogen converted to plasmin?

A

plasminogen activator (tPA)

62
Q

What is tissue plasminogen activator released by?

A

Activated endothelial cells in response to thrombin

63
Q

Plasmin inhibits _____ and degrades

A

inhibits factors V and VIII

degrades fibrin

64
Q

tPA is used to dissolve _____ in brain. Not useful if clot is due to ______

A

clots

hemmorhage

65
Q

tPA is used to dissolve clots if used less than or equal to _____ hours of clot formation

A

4.5 hours

66
Q

Healthy endothelial cells produce ______

A

prostacyclin

67
Q

Prostacyclin does what?

A

inhibits platelets

68
Q

tPA in aqueous humor converts ______ to ______, which keeps ouflow channels clear and activates ________, which plays a role in matrix remodeling

A

plasminogen to plasmin

plasmin activates TGF-Beta

69
Q

chemoattractants attract _______, ________, and ______ to the wound

A

smooth muscle cells
inflammatory cells
fibroblasts

70
Q

______ and growth factors induce smooth muscle cells, inflammatory cells, and fibroblasts to proliferate

A

Mitogens

71
Q

What are the two growth factors that induce Chemoattractant molecules to proliferate?

A

Platelet-derived growth factor

Epidermal growth factor

72
Q

Angiogenesis is mainly involved with ______

A

vascular endothelial growth factor (VEGF)