Circulation > Platelets and Hemostasis- Lecture > Flashcards

Platelets and Hemostasis- Lecture Flashcards

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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 _

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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

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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

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A

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

22
Q

Factor I is _

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A

Factor I is fibrinogen

23
Factor II is _
Factor II is **(pro)thrombin**
24
Factor III is _
Factor III is **tissue factor**
25
Thrombin activates factors _ , _ , _ and _
Thrombin activates factors **V** , **VIII** , **XI** and **XIII** * 5, 8, 11, 13
26
Factor _ is carried by vWF until it gets cleaved/ activated by thrombin
**Factor VIII** is carried by vWF until it gets cleaved/ activated by thrombin
27
The vitamin K dependent coagulation factors are _
The vitamin K dependent coagulation factors are **10, 9, 7, 2** * "Kids Summer Camp- since 1972"
28
Factor Xa is created by joining _ and _ or _ and _
Factor Xa is created by joining **VIIa** and **TF** or by joining **VIIIa** and **IXa** * 7a + tissue factor or 8a + 9a
29
Factor IIa is created by joining _ and _
Factor IIa is created by joining **Va** and **Xa** * 5a + 10a = thrombin
30
Steps of fibrin cross-linking
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
Antithrombin inhibits which 5 coagulation factors?
* **IIa** (2) * **Xa** (10) * VIIa (7) * IXa (9) * XIa (11)
32
Protein S and Protein C are anticoagulant factors that inhibit _ and _
Protein S and Protein C are anticoagulant factors that inhibit **VIIIa** and **Va**
33
To get from fibrinogen to a fibrin clot we need _
To get from fibrinogen to a fibrin clot we need **thrombin**
34
To break up fibrin clots into fibrin split products we need _
To break up fibrin clots into fibrin split products we need **plasmin**
35
Plasmin can be blocked by _
Plasmin can be blocked by **alpha2- antiplasmin**
36
Plasminogen --> plasmin requires _
Plasminogen --> plasmin requires **tPA**
37
tPA can be blocked by _
tPA can be blocked by **PAI-1** (plasminogen activator inhibitor 1)
38
When plasma breaks down fibrin we get _ as byproduct; when plasma breaks down cross-linked fibrin we get _
When plasma breaks down fibrin we get **FDPs** as byproduct; when plasma breaks down cross-linked fibrin we get **D-dimers**
39
_ are the product of cross-linked fibrin breakdown via plasmin
**D-dimers** are the product of cross-linked fibrin breakdown via plasmin
40
_ assess primary hemostasis; they include platelet count, bleeding time, platelet aggregation studies
**Platelet assays** assess primary hemostasis; they include platelet count, bleeding time, platelet aggregation studies
41
_ access secondary hemostasis
**Coagulation assays** access secondary hemostasis * PT * INR * aPTT/PTT * TT * APTT mixing studies
42
To do a coagulation assay on a patient's blood we need to draw blood into a _ tube
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
Why use INR?
**INR** is used to **standardize patient values** * Normal is 0.8-1.2
44
What is the difference between aPTT and PTT?
aPTT stands for *activated* partial thromboplastin time * Instead of having tissue factor to kick things off we use **activator silica**, **phospholipid**, and **calcium**
45
If PTT is corrected following a mixing study it indicates _
If PTT is corrected following a mixing study it indicates that **clotting factor was missing**
46
Normal platelets should aggregate in response to agonists like _ in an assay
Normal platelets should aggregate in response to agonists like **ristocetin, collagen, ADP, epinephrine** in an assay
47
Von willebrand disease or bernard soulier
48
Glanzmann
Circulation
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