Platelet Series

Question 1

The four stages of the Megakaryocyte series

Answer 1

1. Megakaryoblast
2. Promegkaryocyte
3. Megakaryocyte
4. Platelets (Thrombocyte)

Question 2

Name the megakaryocyte:

• Nucleus may be lobulated
• Non-granular cytoplasm; may have small, blunt pseudopods

Answer 2

Megakaryoblast

Question 3

Name the megakaryocyte:

• Nucleus may be irregular, but not lobulated
• In the cytoplasm, Azurophilic granules appear… when DNA synthesis ceases

Answer 3

Promegakaryocyte

Question 4

Name the megakaryocyte:

• multilobed nucleus (endomitosis)
• Cytoplasm is granular
• Largest (normal) hemapoietic cell in Bone Marrow
• Note: cytoplasm of this cell breaks off to form platelets

Answer 4

Megakaryocyte

Question 5

Name the megakaryocyte:
-No nucleus
-Under Wright Stain morphology,;
  -granulomere
  -hyalomere
Size- 1-4 microns

Answer 5

Mature Platelet (Thrombocyte)

Question 6

Mechanism of Platelet Release

Answer 6

• Budding or shedding of platelets from the mature megakaryocyte thru endothelial gaps in the bone marrow sinusoid
• Platelets are NOT STORED in the Bone Marrow
• One Megakaryocyte can produce 2,000 - 4,000 platelets

Question 7

The two sites of thrombopoeitic production

Answer 7

1. Medullary- Bone Marrow

2. Extramedullary- Lung

Question 8

Regulatory Mechanism of Thrombopoeisis

Answer 8

Thrombopoeitin

• Hormonal Regulatory Factor
• Produced predominately by kidney

Question 9

Name the two pools in which platelets are distributed

Answer 9

1. Circulatory Pool- 2/3 of platelet mass
2. Splenic Pool- 1/3 of platelet mass
   - possibly the younger platelets

• The two pools exchange freely

Question 10

Platelet Life Span

Answer 10

8-12 days, if not used in clotting

Platelet destruction:

• senescence by RES
• Random loss via coagulation

Question 11

Four functions of Platelets

Answer 11

1. Primary Hemostasis- formation of a platelet plug
2. Secondary Hemostasis- platelet plug stabilized by fibrin
3. Shrinkage of Clot- by thrombosthenin
4. Maintain Vessel Integrity- platelets repair small vessel injuries by filling in gaps in endothelial lining

Question 12

What is the diluting fluid used in manual platelet counts?

Answer 12

Ammonium Oxalate

will lyse RBCs

Question 13

What is the anticoagulant of choice when performing an automated platelet count?

Answer 13

EDTA

- in most people, it prevents the clumping of platelets

Question 14

What can cause a FALSELY HIGH platelet count?

Answer 14

Hemolyzed sample

-must redraw specimen

Question 15

What can cause a FALSELY LOW

Answer 15

1. Platelet clumps
2. Platelet satellitism
   - must redraw specimen with sodium citrate tube for both issues
3. Giant platelets
   - must perform manual method to get a valid count

Question 16

If you notice that no platelets are seen when performing a differential on a capillary puncture specimen, what must you do first?

Answer 16

Check the edges and the tail of the slide for platelet clumping (LPF)

Question 17

What is the reference values for platelets?

Answer 17

150,000-450,000

Question 18

Define endomitosis:

Answer 18

Nuclear material replicates, but cell itself does not divide

Question 19

Define hemostasis

Answer 19

the stopping of a flow of blood

Question 20

Define platelet satellitism

Answer 20

Platelet adherence to polymorphonuclear leukocytes

Question 21

Define thrombosthenin

Answer 21

A contractile protein in platelets that is active in the formation of blood clots

Question 22

Define thrombocyte

Answer 22

Another name for a mature platelet