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MHD1/Pharm1 Exam 4 > (MHD) Normal Hemostasis/ Thrombosis I and II > Flashcards

(MHD) Normal Hemostasis/ Thrombosis I and II Flashcards

1
Q

Normal vs Abnormal Hemostasis

A

Normal Hemostasis: the complex process by which ruptured vessels undergo changes which prevent blood loss (i.e. formation of hemostatic plug)

Abnormal Hemostasis: the process by which blood forms a clot within intact blood vessels (aka thrombosis)

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2
Q

Hemostasis is dependent upon what three major entities?

A
  1. Blood vesel wall (endothelium and sub endothelial substances)
  2. Platelets
  3. Coagulation and fibrinolytic systems
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3
Q

The (4) main components of the hemastatic response

A
  1. Vasoconstriction
  2. Primary hemostasis
  3. Secondary hemostasis
  4. Formation of platelet-thrombin plug (permanent plug)
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4
Q

____________ is released from the endothelial cells in distress

What is this agent and what does it do?

A

Endothelin

It is a potent vasoconstricting agent

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5
Q

The (5) steps of primary hemostasis

A
  1. Platelets adhere to the damaged vessels (bind vWF)
  2. Platelets undergo shape change from discoid formation
  3. Light and dense granules release important cytokines (ADP, thromboxane A2, serotonin etc.)
  4. Activated platelets recruit other platelets
  5. Hemostatic plug formation
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6
Q

Describe the process of secondary hemostasis

A

Tissue factor is released from endothelial cells at the site of injury and combines with platelet factors to initiate the plasma coagulation cascade, ultimately causing a thrombin to form.

These coagulation proteins form complexes on the platelet surface utililizing the phospholipids of the platelet membrane.

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7
Q

Formed fibrin is polymerized by…

A

Factor XIIIa

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8
Q

During the formation of the platelet-thrombin plug (permanent plug), what are the roles of thrombin (2)

A
  1. Thrombin stimulates recruitment and activation of additional platelets
  2. Thrombin enzymatically converts fibrinogen to fibrin
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9
Q

The (2) general pathways that the endothelium uses to modulate elements of the hemostasis-coagulation sequence.

A
  1. Anti-thrombotic effect (normal state)
  2. Prothrombotic effect (response to injured endothelium)
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10
Q

Name the (3) components of the antithrombotic effect of the endothelium

A
  1. Antiplatelet effect
  2. Anticoagulant effect
  3. Fibrinolytic-effect
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11
Q

Describe the antiplatelet effect of the antithrombotic effect

A

Intact endothelium prevents platelets and coagulation proteins from coming into contact with subendothelial collagen and secretes prostacyclin and NO which prevent platelet aggregation.

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12
Q

Describe the role of Heparin-like molecules in the anticoagulant effect of the antithrombotic effect

A

Heparin-like molecules combine with antithrombin to inactivate factors Xa and IXa

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13
Q

Describe the role of Thrombomodulin in the anticoagulant effect of the antithrombotic effect, particularly as it relates to Protein C and its function.

A

Thrombomodulin combines with thromobin creating a complex that activates protein C. Protein C mediates proteolytic degradation of Factor Va and VIIIa.

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14
Q

What is the role of protein S?

A

It is a cofactor for protein C activation

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15
Q

Describe the Fibrinolytic effect of the antithrombotic effect

(describe the role of plasminogen and plasmin)

A

Among a number of other functions, endothelial cells also secrete plasminogen activators (t-PA). Plasminogen is converted to plasmin which dissolves the clot.

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16
Q

What (2) things do endothelial cells secrete to promote the prothrombotic effect?

A
  1. von Willebrand factor
  2. Tissue factor
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17
Q

von Willebrand factor

A

A protein which forms a molecular bridge between platelets and sub-endothelial collagen, allowing platelet adhesion to endothelial cells to occur.

Secreted by endothelial cells during Prothrombotic effect.

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18
Q

Tissue factor

(what does it do? what can stimulate its secretion?)

A

Synthesized and secreted by the endothelial cells. Activates the extrinsic sequence of the coagulation cascade, thereby promoting the generation of thrombin and formation of a clot.

Cytokines released by injured endothelial cells can stimulate cells to synthesize more tissue factor

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19
Q

What is the key difference between primary and secondary hemostasis?

A

Fibrin is only involved in secondary hemostasis– NOT primary

20
Q

T-PA

A

Tissue Plasminogen Activator

Also known as fibrinolysis. Functions to dissolve clot after its function has been served. This is important because if it is not broken down you risk thrombosis or embolus.

21
Q

Distinguish between the two types of granules found in platelet cytoplasma

A

Light granules: aka ALPHA - contain platelet factor 4, fibrinogen and other factors

Dark (dense) granules- aka BETA- contain ADP, calcium, serotonin, etc.

22
Q

Name the 2 most key platelet receptors

A
  • Glycoprotein IIb/IIIa
  • Glycoprotein Ib
23
Q

What is von Willebrand factor bound to? (2)

A

It binds to the surface of exposed subendothelium and to the GpIb receptor of the platelet

24
Q

What is the GpIIb-IIIa receptor bound to and what is its function?

A

It binds to fibrinogen, which is bound to the GpIIb-IIIa receptor of another platelet, allowing for platelet aggregation

25
Q

Bernard-Soulier syndrome

A

Deficiency of GpIb, which keeps platelet from binding von Willebrand factor (leading to loss of clotting ability)

26
Q

Glanzmann thrombasthenia

A

Deficiency of GpIIb-IIIa complex which leads to a loss of fibrinogen mediated aggregation of the platelets.

27
Q

What are the 3 broad steps that lead to platelets forming a clot

A

Platelet adhesion, activation and aggregation

28
Q

Activation of platelets is intiated by molecules binding with platelet ______________ receptors.

A

GP-Ib receptors

29
Q

Upon activation platelets release…

A

granular content including ADP, calcium, and thromboxane A2

30
Q

Thrombin functions to…

A

…convert fibrinogen to fibrin. Fibrin then surrounds and structurally holds platelets together to form the plug.

31
Q

What activates the intrinsic pathway of the coagulation cascade? How is the functioning of this pathway measured?

A

It is activated by the patients own endogenous activating mechanisms.

Measured by the aPTT test

32
Q

What activates the extrinsic pathway of the coagulation cascade? What test is used to measure the state of this pathway? What is are the 2 key factors associated with this pathway

A

TIssue injury

PT/ INR

Associated with tissue factor and factor VII (or VIIa)

33
Q

What is the key factor which starts off the common pathway of the coagulation cascade?

A

Factor X

34
Q

Factors of the coagulation cascade are all ________ proteins, except for factor __________ which is a _________ protein.

A
  • serine
  • XIIIa (fibrin stabilizing factor)
  • transaminase
35
Q

What factors make up the prothrombin group of coagulation?

All of these proteins contain ____________ which is needed for the binding of _________.

A
  • Factors II, VII, IX and X
  • gamma-carboxy glutamic acid
  • calcium
36
Q

Association between liver and bleeding issues

A

The liver is key in the production of prothrombin group factors, so liver diseases may result in decreased clotting ability.

37
Q

Name the factors which make up the contact group of the coagulation cascade.

A

Factors XI, XII, Fletcher factor (Prekallikrein) and Fitzgerald factor (HMW Kininogen)

(these last two play a key role in the intrinsic pathway)

38
Q

Name the key inhibitors of the coagulation system

A
  • Antithrombin III (AT)
  • Tissue factor pathway inhibitor (TFPI)
39
Q

Antithrombin function

A

A plasma inhibitor which also mediates the anticoagulant actions of heparin.

40
Q

Fibrinolytic system

A

A network of enzymes that are responsible for the dissolution of a formed clot.

41
Q

What is the key protein which serves to lyse clots?

A

Plasmin (aka fibrinolysin)

42
Q

Name the key fibrinolytic system inhibitors

A
  1. Plasminogen activator inhibitor (PAI)
  2. a2-antiplasmin
43
Q

The 3 factors which make up virchow’s thrombosis triad

A
  1. endothelial injury
  2. hypercoagulability
  3. abnormal blood flow
44
Q

Molecular thrombophilias

Give an example

A

Molecular predisposition to thrombosis

ex. activated protein C deficiency [APC syndrome]

45
Q

Where does VWF come from?

A
  1. Platelets
  2. Endothelial Cell (Weibel-Palade body)

MHD1/Pharm1 Exam 4 (26 decks)

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