Platelets and Hemostasis- Lecture Flashcards

1
Q

_ is the mechanism by which bleeding comes to an end after vessel injury –> clot formation

A

Hemostasis is the mechanism by which bleeding comes to an end after vessel injury –> clot formation

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2
Q

3 broad steps of hemostasis

A
  1. Blood vessel constriction
  2. Platelet plug formation (primary hemostasis)
  3. Fibrin formation (secondary hemostasis)
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3
Q

Platelets are fragments of _

A

Platelets are fragments of megakaryocyte cytoplasm

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4
Q

Thrombopoiesis is the process by which _

A

Thrombopoiesis is the process by which megakaryocytes bud off fragments of their cytoplasm

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5
Q

The hormonal regulator of platelet production is _

A

The hormonal regulator of platelet production is thrombopoietin

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6
Q

_ is a platelet count under 150,000

A

Thrombocytopenia is a platelet count under 150,000
* Can lead to excess bleeding

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7
Q

_ is a platelet count > 400,000

A

Thrombocytosis is a platelet count > 400,000
* This can lead to excess clotting

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8
Q

Platelet structure can be divided into two sections _ and _

A

Platelet structure can be divided into two sections granulomere and hyalomere

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9
Q

The granulomere contains the _

A

The granulomere contains the alpha and dense granules

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10
Q

The hyalomere contains the _

A

The hyalomere contains the cytoskeletal fibers which allow the platelet to contract

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11
Q

4 factors secreted by the alpha granules

A

Alpha granules secrete:
1. PDGF
2. PF4
3. vWF
4. P-selectin

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12
Q

4 factors secreted by the dense granules

A

Dense granules secrete:
1. Serotonin
2. ADP
3. ATP
4. Calcium

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13
Q

vWF is secreted by _ granules

A

vWF is secreted by alpha granules

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14
Q

The platelet has a GPIb receptor for binding _

A

The platelet has a GPIb receptor for binding vWF during the adhesion stage

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15
Q

The platelet has a GPIIb/IIIa receptor for binding _

A

The platelet has a GPIIb/IIIa receptor for binding fibrinogen during the aggregation step

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16
Q

The platelet has a P2Y12 receptor that for binding _

A

The platelet has a P2Y12 receptor that for binding ADP during aggregation

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17
Q

What prevents platelets from adhering to the blood vessels under normal conditions without injury?

A

Endothelial cells!

  1. Secretion of products that prevent platelets from activating:
    * Prostacyclin
    * Nitric oxide
    * Endothelial ADPase
  2. Hide collagen and vWF beneath their surface
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18
Q

When blood vessel injury occurs, collagen becomes exposed and binds vWF; platelets can then start to stick to the site of injury by grabbing onto vWF with their _ receptors

A

When blood vessel injury occurs, collagen becomes exposed and binds vWF; platelets can then start to stick to the site of injury by grabbing onto vWF with their GPIb receptors

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18
Q

After vWF – GPIb binding occurs we next get _

A

After vWF – GPIb binding occurs we next get platelet granule release
* Alpha granules
* Dense granules
* Thromboaxane A2
* Coagulation factors

Platelets also change their shape to increase their surface area

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18
Q

Now (during platelet activation stage) platelets express their _ receptors to attract more platelets and get ready to aggregate

A

Now (during platelet activation stage) platelets express their GPIIb/IIIa receptors to attract more platelets and get ready to aggregate
* Thrombin also activates platelet membrane receptors

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19
Q

In order for platelets to aggregate and form the soft platelet plug, we need binding between _ receptors and _

A

In order for platelets to aggregate and form the soft platelet plug, we need binding between GPIIb/IIIa receptors and fibrinogen

20
Q

After the soft platelet plug is created, the next step is the _ , which turns _ into _ to form a strong network between platelets and stabilizes the clot

A

After the soft platelet plug is created, the next step is the coagulation cascade, which turns fibrinogen into fibrin to form a strong network between platelets and stabilizes the clot

21
Q

Clotting factors are really special enzymes called _ that activate more downstream factors

A

Clotting factors are really special enzymes called serine proteases that activate more downstream factors

22
Q

Factor I is _

A

Factor I is fibrinogen

23
Q

Factor II is _

A

Factor II is (pro)thrombin

24
Q

Factor III is _

A

Factor III is tissue factor

25
Q

Thrombin activates factors _ , _ , _ and _

A

Thrombin activates factors V , VIII , XI and XIII
* 5, 8, 11, 13

26
Q

Factor _ is carried by vWF until it gets cleaved/ activated by thrombin

A

Factor VIII is carried by vWF until it gets cleaved/ activated by thrombin

27
Q

The vitamin K dependent coagulation factors are _

A

The vitamin K dependent coagulation factors are 10, 9, 7, 2
* “Kids Summer Camp- since 1972”

28
Q

Factor Xa is created by joining _ and _ or _ and _

A

Factor Xa is created by joining VIIa and TF or by joining VIIIa and IXa
* 7a + tissue factor or 8a + 9a

29
Q

Factor IIa is created by joining _ and _

A

Factor IIa is created by joining Va and Xa
* 5a + 10a = thrombin

30
Q

Steps of fibrin cross-linking

A
  1. Fibrinogen
  2. Thrombin comes in and makes a fibrin monomer
  3. The fibrin monomers come together to make fibrin polymers
  4. Factor XIIIa stabilizes the fibrin polymer
31
Q

Antithrombin inhibits which 5 coagulation factors?

A
  • IIa (2)
  • Xa (10)
  • VIIa (7)
  • IXa (9)
  • XIa (11)
32
Q

Protein S and Protein C are anticoagulant factors that inhibit _ and _

A

Protein S and Protein C are anticoagulant factors that inhibit VIIIa and Va

33
Q

To get from fibrinogen to a fibrin clot we need _

A

To get from fibrinogen to a fibrin clot we need thrombin

34
Q

To break up fibrin clots into fibrin split products we need _

A

To break up fibrin clots into fibrin split products we need plasmin

35
Q

Plasmin can be blocked by _

A

Plasmin can be blocked by alpha2- antiplasmin

36
Q

Plasminogen –> plasmin requires _

A

Plasminogen –> plasmin requires tPA

37
Q

tPA can be blocked by _

A

tPA can be blocked by PAI-1 (plasminogen activator inhibitor 1)

38
Q

When plasma breaks down fibrin we get _ as byproduct; when plasma breaks down cross-linked fibrin we get _

A

When plasma breaks down fibrin we get FDPs as byproduct; when plasma breaks down cross-linked fibrin we get D-dimers

39
Q

_ are the product of cross-linked fibrin breakdown via plasmin

A

D-dimers are the product of cross-linked fibrin breakdown via plasmin

40
Q

_ assess primary hemostasis; they include platelet count, bleeding time, platelet aggregation studies

A

Platelet assays assess primary hemostasis; they include platelet count, bleeding time, platelet aggregation studies

41
Q

_ access secondary hemostasis

A

Coagulation assays access secondary hemostasis
* PT
* INR
* aPTT/PTT
* TT
* APTT mixing studies

42
Q

To do a coagulation assay on a patient’s blood we need to draw blood into a _ tube

A

To do a coagulation assay on a patient’s blood we need to draw blood into a blue-top tube containing citrate
* The citrate prevents the blood from clotting by removing calcium

43
Q

Why use INR?

A

INR is used to standardize patient values
* Normal is 0.8-1.2

44
Q

What is the difference between aPTT and PTT?

A

aPTT stands for activated partial thromboplastin time
* Instead of having tissue factor to kick things off we use activator silica, phospholipid, and calcium

45
Q

If PTT is corrected following a mixing study it indicates _

A

If PTT is corrected following a mixing study it indicates that clotting factor was missing

46
Q

Normal platelets should aggregate in response to agonists like _ in an assay

A

Normal platelets should aggregate in response to agonists like ristocetin, collagen, ADP, epinephrine in an assay

47
Q
A

Von willebrand disease or bernard soulier

48
Q
A

Glanzmann