Hemostasis: Approach to a Patient Flashcards Preview

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Flashcards in Hemostasis: Approach to a Patient Deck (41)
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1

What cell is described as small anuclear discoid or 2-3 microns and is derived from megakaryocytes?

Platelets

2

How long does it take for a platelet to mature?

How long is the lifespan of a platelet?

-4-5 days
-9-10 days

3

What percentage of platelets are found in circulation?

In the spleen?

80% in circulation

20% in spleen

4

What are megathrombocytes?

Newly formed platelets that are large in size

5

Platelets contain ____________ but do not contain ____________

Mitochondria

Nuclei

6

What are the three kinds of functional granules found in a platelet?

Dense
Alpha
Lysosomal granules

7

What do dense granules contain?

ATP
ADP
Serotonin
Calcium

8

What do alpha-granules contain?

A number of proteins essential for platelet funciton including procoagulant proteins, plaelet-specific factors for platelet activation, and growth favtors

9

What do lysosomal granules contain?

Acid hydrolases

10

What is the function of surface-connected canalicular systems?

These extensive systems of internal membrane tunnels are tunnels through which the contents of the platelet granules are extruded during platelet aggregation and secretion

11

What are the main functions of platelets?

Adhesion to the vascular subendothelium at sites of injury

Activation of intracellular signaling pathways leading to cytoskeletal changes and release of intracellular gransules

Aggregation to form the platelet plug

Support thrombin generation

12

Intact endothelial cells can produce what two compounds that act as inhibitors of platelet activation?

Nitric oxide and prostacyclin

13

What factor do platelets bind in order to adhere to injured endothelium?

von Willebrand's Factor

14

What protein is used to link vWF to platelets?

GP1b

15

What is the role of GPIIb-IIIa in platelet and vWF adhesion?

The enzyme increases its affinity

16

What happens after platelets adhere to the injured vessel wall?

They undergo a shape change through cytoskeletal activation, becoming more spherical with extended pseudpods and spread over the exposed subendothelium

Then they release the granules

17

Platelets adhere to each other through which protein?

Fibrinogen is a cross-linker between GPIIb-IIIa

18

What converts fibrinogen to fibrin to form a stabilized plaatelet plug?

Thrombin

19

What two tests are commonly used to evaluate platelet function?

Platelet count as a part of a CBC
Bleeding time which will be prolonged if

20

This type of QUALITATIVE platelet disorder is characterized by as a disorder in adhesion. It is the most common congenital bleeding disorder. It leads to a primary and secondary bleeding disorder. What is it?

Von Willebrands disease.

21

What test can you use to test the activity of vWF?

Ristocetin cofactor activity test

22

What drug can you use to treat type I vWD?

DDAVP because it enhances the release of vWF from endothelial stores

23

What is Bernard-Soulier syndrome?

A rare autosomal recessive disorder where expression of GP1b on the platelet surface is reduced

Abnormal ristocetin test

24

What is gray platelet syndrome?

Deficiency in dense granules or alpha-granules

25

Afibrogenemia is a rare inherited defect that results in a decreased amount of what protein?

Fibinogen

26

What rare autosomal recessive bleeding disorder is characterized by the absence of defective GPIIb-IIIa?

Glanzmann thrombasthenia

27

What is the normal platelet range?

150,000-400,000

28

At what platelet count could you expect patients to spontaneously hemorrhage?

29

At what platelet count could you expect patients to spontaneously hemorrhage intracranially?

10-20,000

30

What is the most common cause of thrombocytopenia due to increased destruction?

Immune thrombocytopenic purpura