Platelet Series

Question 1

Describe the nuclear and cytoplasmic appearance of the megakaryoblast

Answer 1

N: may be lobulated
C: may have small, blunt pseudopods and is nongranular

Question 2

Describe the nuclear and cytoplasmic appearance of the promegakaryocyte

Answer 2

N: may be irregular, but not lobulated
C: azurophilic (burgundy colored) granules appear when DNA synthesis ceases

Question 3

Describe the nuclear and cytoplasmic appearance of the megakaryocyte

Answer 3

N: multilobed due to endomitosis
C: granular

Question 4

Describe the nuclear and cytoplasmic appearance of the thrombocytes

Answer 4

N: no nucleus
C: light blue to colorless w/ abundant red to violet colored granules

Question 5

How are platelets released?

Answer 5

Platelets bud or shed from mature megakaryocyte thru endothelial gaps in the BM sinusoid
- One megakaryocyte can produce 2000-4000 platelets

Question 6

Where does medullary thrombopoiesis occur?

Answer 6

Bone marrow

Question 7

Where does extramedullary thrombopoiesis occur?

Answer 7

Lung

Question 8

Hormonal regulatory factor produced predominantly by the kidney

Answer 8

Thrombopoietin

Question 9

Two pools where platelets are distributed

Answer 9

Circulatory pool (2/3 of platelet mass)
Splenic pool (1/3 of platelet mass)

Question 10

The average platelet’s lifespan

Answer 10

8-12 days if not used in clotting

Question 11

How are platelets removed at the end of their lifespan (2)?

Answer 11

1. Senescence…damaged/dead platelets phagocytized and removed by RES
2. Random loss via coagulation

Question 12

4 functions of platelets

Answer 12

1. primary hemostasis → formation of platelet plug
2. Secondary hemostasis → plaetelet 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 until more endothelial cells grow

Question 13

Diluting fluid used when performing manual platelet count

Answer 13

Ammonium oxalate

Question 14

Anticoagulant of choice for cell counting, including electronic platelet counts

Answer 14

EDTA

Question 15

Giant platelets

• Effect on electronic platelet count
• Protocol for obtaining valid platelet count

Answer 15

• Falsely ↓ electronic platelet count

- Perform manual (Unopette) method for valid count

Question 16

Why do giant platelets falsely ↓ the electronic platelet count?

Answer 16

Some coagulation diseases cause patients to have giant platelets too large for the Coulter counter’s threshold, therefore they’re missed

Question 17

Hemolyzed sample

• Effect on electronic platelet count
• Protocol for obtaining valid platelet count

Answer 17

• Falsely ↑ electronic platelet count

- Redraw specimen

Question 18

Why do hemolyzed samples falsely ↑ electronic platelet counts?

Answer 18

↓ RBC, ↓ hematocrit → H&H not being balanced

Question 19

Platelet clumps

• Effect on electronic platelet count
• Protocol for obtaining valid platelet count

Answer 19

• Falsely ↓ electronic platelet count

- Redraw specimen w/ sodium citrate (light blue tube) and multiply count by 1.1 for valid count

Question 20

Platelet satellitism

• Effect on electronic platelet count
• Protocol for obtaining valid platelet count

Answer 20

Falsely ↓ electronic platelet count

- Redraw specimen w/ sodium citrate (light blue tube) and multiply count by 1.1 for valid count

Question 21

How do platelet clumps and platelet satellitism occur?

Answer 21

An in vitro phenomena w/ EDTA

Question 22

No platelets are seen when performing a differential prepared from a capillary puncture, what do you do?

Answer 22

Double check platelet counts w/ a slide estimate (especially if it’s a finger or heel stick)

Question 23

Formula for platelet estimate

Answer 23

average x # of platelets x 20000

Question 24

Reference value for platelet counts

Answer 24

150,000-450,000/mm^3

Question 25

When nuclear material replicates, but cell itself doesn't divide; creates a megakarycote w/ multilobed nucleus and progressive increase in cytoplasm

Answer 25

Endomitosis

Question 26

Process by which a series of platelet, endothelial cell, and plasma enzyme systems prevent blood loss through clot formation

Answer 26

Hemostasis

Question 27

Ab-mediated in vitro adhesion of platelets to segmented neutrophils; occurs primarily in specimens anticoagulated w/ EDTA and causes pseudothrombocytopenia

Answer 27

Platelet satellitism

Question 28

Coagulation/platelet factor that shrinks clots

Answer 28

Thrombosthenin

Question 29

aka platelet

Answer 29

Thrombocyte