13. Platelet Gel- Exam 3 Flashcards
Young, fecund, robust, inactivated platelets are what size
1-3 μm discoids
platelet concentration and life span
Humans: Normally ~ 150,000-300,000/ml of blood
Life span~one week
what do α-granules contain
clotting factors, growth factors, and various other proteins
what do Dense granules contain
ADP, ATP, Serotonin, and Calcium
young VS old platelets [weight/size]
Young platelets are large and heavy (dense)
Old platelets are small and light
Young large platelets aggregate how much faster than older platelets
3-5 x
Young platelets release how much more ATP and ADP than do older platelets
ATP (4-8 x)
ADP (4-6 x)
Old platelets require substantially greater amounts of ____ to be activated than do young platelets
ADP
What are the 7 steps platelets go through- starting with the wound and ending with platelet aggregation
- Wound
- Exposes subendothelial collagen
- Binds von Willebrand Factor
- Platelet adhesion to blood vessel wall via GP IIb/IIIa
- Platelet activation
- Platelet cytoskeleton (via actin and myosin) expands
from a disc to a multi-pseudopodal sticky blob - Platelet aggregation
why do aggregated platelets release serotonin
Vasoconstriction
why do aggregated platelets release ADP
Recruits other platelets to aggregate and degranulate
why do aggregated platelets release thromboxane
Platelet aggregation and PGF release
PDGF: Platelet-Derived Growth Factor=
STRONGLY mitogenic and chemotactic for leukocytes
-By itself PDGF application doubles the rate of collagen
deposition in a wound
TGF-β: Transforming Growth Factor-Beta=
Also strongly mitogenic
-Allows damaged (irradiated, corticosteroid-treated)
tissues to revert to normalized collagen deposition
Attracted neutrophils and macrophages release what?
a host of other healing factors
Cells expressing the CD34 protein are concentrated where?
in the mononuclear layer of platelet concentrate
Cells expressing the CD34 protein are what?
stem cell “markers” and are important for other cells’ adhesion/chemotaxis
Platelet Rich Plasma (PRP)=
“The components of whole blood remaining after the removal of (most of) the red cells”
- The buffy coat (white cells and platelets) extending ??? into the top of the red cell column
- PLUS all of the plasma
Platelet Poor Plasma (PPP)=
“Plasma layer without the buffy coat”
-So…you get lots of fibrinogen & coagulation factors but no cells
Platelet concentrate: Buffy coat =
leukocytes + platelets
Platelet concentrate: Leukocyte=
neutrophils, eosinophils, basophils, macrophages, B- and T-lymphocytes
Platelet Gel (PG)=
Platelet Concentrate with enough fibrinogen (2-4mg/ml) to “set up” when combined with an activator
-Platelets 2-6x over baseline
Platelet Gel ‘activator’
“Activator” = Thrombin (bovine or human), Calcium (usually CaCl₂) or Collagen
How many platelets do you need:
Theory 1) Increase in multiples above baseline
- Typically 2-6 times above baseline
- Evidence suggests >6x actually delays healing…why?
- Theory suggests possible up-regulation of other tissues to “factors” in the presence of thrombocytopenia
