Platelets and Hemostasis- Lecture

Question 1

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

Answer 1

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

Question 2

3 broad steps of hemostasis

Answer 2

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

Question 3

Platelets are fragments of _

Answer 3

Platelets are fragments of megakaryocyte cytoplasm

Question 4

Thrombopoiesis is the process by which _

Answer 4

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

Question 5

The hormonal regulator of platelet production is _

Answer 5

The hormonal regulator of platelet production is thrombopoietin

Question 6

_ is a platelet count under 150,000

Answer 6

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

Question 7

_ is a platelet count > 400,000

Answer 7

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

Question 8

Platelet structure can be divided into two sections _ and _

Answer 8

Platelet structure can be divided into two sections granulomere and hyalomere

Question 9

The granulomere contains the _

Answer 9

The granulomere contains the alpha and dense granules

Question 10

The hyalomere contains the _

Answer 10

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

Question 11

4 factors secreted by the alpha granules

Answer 11

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

Question 12

4 factors secreted by the dense granules

Answer 12

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

Question 13

vWF is secreted by _ granules

Answer 13

vWF is secreted by alpha granules

Question 14

The platelet has a GPIb receptor for binding _

Answer 14

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

Question 15

The platelet has a GPIIb/IIIa receptor for binding _

Answer 15

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

Question 16

The platelet has a P2Y12 receptor that for binding _

Answer 16

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

Question 17

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

Answer 17

Endothelial cells!

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

Question 18

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

Answer 18

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

Question 18

After vWF – GPIb binding occurs we next get _

Answer 18

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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

Question 22

Factor I is _

Answer 22

Factor I is fibrinogen

Question 23

Factor II is _

Answer 23

Factor II is **(pro)thrombin**

Question 24

Factor III is _

Answer 24

Factor III is **tissue factor**

Question 25

Thrombin activates factors _ , _ , _ and _

Answer 25

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

Question 26

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

Answer 26

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

Question 27

The vitamin K dependent coagulation factors are _

Answer 27

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

Question 28

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

Answer 28

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

Question 29

Factor IIa is created by joining _ and _

Answer 29

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

Question 30

Steps of fibrin cross-linking

Answer 30

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

Question 31

Antithrombin inhibits which 5 coagulation factors?

Answer 31

* **IIa** (2) * **Xa** (10) * VIIa (7) * IXa (9) * XIa (11)

Question 32

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

Answer 32

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

Question 33

To get from fibrinogen to a fibrin clot we need _

Answer 33

To get from fibrinogen to a fibrin clot we need **thrombin**

Question 34

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

Answer 34

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

Question 35

Plasmin can be blocked by _

Answer 35

Plasmin can be blocked by **alpha2- antiplasmin**

Question 36

Plasminogen --> plasmin requires _

Answer 36

Plasminogen --> plasmin requires **tPA**

Question 37

tPA can be blocked by _

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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

Question 41

_ access secondary hemostasis

Answer 41

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

Question 42

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

Answer 42

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

Question 43

Why use INR?

Answer 43

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

Question 44

What is the difference between aPTT and PTT?

Answer 44

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

Question 45

If PTT is corrected following a mixing study it indicates _

Answer 45

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

Question 46

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

Answer 46

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

Answer 47

Von willebrand disease or bernard soulier

Answer 48

Glanzmann