Platelet Series Flashcards
Describe the nuclear and cytoplasmic appearance of the megakaryoblast
N: may be lobulated
C: may have small, blunt pseudopods and is nongranular
Describe the nuclear and cytoplasmic appearance of the promegakaryocyte
N: may be irregular, but not lobulated
C: azurophilic (burgundy colored) granules appear when DNA synthesis ceases
Describe the nuclear and cytoplasmic appearance of the megakaryocyte
N: multilobed due to endomitosis
C: granular
Describe the nuclear and cytoplasmic appearance of the thrombocytes
N: no nucleus
C: light blue to colorless w/ abundant red to violet colored granules
How are platelets released?
Platelets bud or shed from mature megakaryocyte thru endothelial gaps in the BM sinusoid
- One megakaryocyte can produce 2000-4000 platelets
Where does medullary thrombopoiesis occur?
Bone marrow
Where does extramedullary thrombopoiesis occur?
Lung
Hormonal regulatory factor produced predominantly by the kidney
Thrombopoietin
Two pools where platelets are distributed
Circulatory pool (2/3 of platelet mass) Splenic pool (1/3 of platelet mass)
The average platelet’s lifespan
8-12 days if not used in clotting
How are platelets removed at the end of their lifespan (2)?
- Senescence…damaged/dead platelets phagocytized and removed by RES
- Random loss via coagulation
4 functions of platelets
- primary hemostasis → formation of platelet plug
- Secondary hemostasis → plaetelet plug stabilized by fibrin
- Shrinkage of clot by thrombosthenin
- Maintain vessel integrity → platelets repair small vessel injuries by filling in gaps in endothelial lining until more endothelial cells grow
Diluting fluid used when performing manual platelet count
Ammonium oxalate
Anticoagulant of choice for cell counting, including electronic platelet counts
EDTA
Giant platelets
- Effect on electronic platelet count
- Protocol for obtaining valid platelet count
- Falsely ↓ electronic platelet count
- Perform manual (Unopette) method for valid count
Why do giant platelets falsely ↓ the electronic platelet count?
Some coagulation diseases cause patients to have giant platelets too large for the Coulter counter’s threshold, therefore they’re missed
Hemolyzed sample
- Effect on electronic platelet count
- Protocol for obtaining valid platelet count
- Falsely ↑ electronic platelet count
- Redraw specimen
Why do hemolyzed samples falsely ↑ electronic platelet counts?
↓ RBC, ↓ hematocrit → H&H not being balanced
Platelet clumps
- Effect on electronic platelet count
- Protocol for obtaining valid platelet count
- Falsely ↓ electronic platelet count
- Redraw specimen w/ sodium citrate (light blue tube) and multiply count by 1.1 for valid count
Platelet satellitism
- Effect on electronic platelet count
- Protocol for obtaining valid platelet count
Falsely ↓ electronic platelet count
- Redraw specimen w/ sodium citrate (light blue tube) and multiply count by 1.1 for valid count
How do platelet clumps and platelet satellitism occur?
An in vitro phenomena w/ EDTA
No platelets are seen when performing a differential prepared from a capillary puncture, what do you do?
Double check platelet counts w/ a slide estimate (especially if it’s a finger or heel stick)
Formula for platelet estimate
average x # of platelets x 20000
Reference value for platelet counts
150,000-450,000/mm^3
When nuclear material replicates, but cell itself doesn’t divide; creates a megakarycote w/ multilobed nucleus and progressive increase in cytoplasm
Endomitosis
Process by which a series of platelet, endothelial cell, and plasma enzyme systems prevent blood loss through clot formation
Hemostasis
Ab-mediated in vitro adhesion of platelets to segmented neutrophils; occurs primarily in specimens anticoagulated w/ EDTA and causes pseudothrombocytopenia
Platelet satellitism
Coagulation/platelet factor that shrinks clots
Thrombosthenin
aka platelet
Thrombocyte
