Platelet Ultrasctructure Flashcards
Platelet is anatomically divided into four areas:
- Peripheral Zone
- Sol Gel Zone
- Organelle Zone
- Membranous System
Under the Peripheral Zone
a. Glycocalyx
b. Plasma Membrane
Under the Sol Gel Zone
a. Microtubules
b. Microfilaments
Under the Organelle Zone
a. Mitochondria
b. a-granules
c. Dense granules
d. Lysosomes
Under the Membranous System
a. Dense tubular system
b. Surface connecting canalicular system
Outer surface, fuzzy containing primarily composed of glycoproteins
Glycocalyx
Bilayer of phospholipids
Platelet Membranes
Predominant lipids in Platelet Membrane:
a. Phospholipids
b. Cholesterol
A predominant lipid that forms the basic structure
Phospholipids
A predominant lipid that distributes asymmetrically throughout the phospholipids
Cholesterol
What are the Neutral Phospholipids (Predominant in the plasma layer)
- Phosphatidyl choline
B. Sphingomyelin
Anionic or polar phospholipids (Predominates the cytoplasmic layer)
- Phosphatidylinositol
- Phosphatidylethanolamine
- Phosphatidylserine
Supplies arachidonic acid
Phosphatidylinositol
Flips to the external surface and is responsible in the assembly of the coagulation factor complexes in the surface.
Phosphatidylserine
Stabilizes the membrane, maintains fluidity, and helps control the transmembranous passage of materials through the selectively permeable plasma membrane.
Cholesterol
Maintains the platelet’s discoid shape
Microtubules
Microfilaments is composed of
Actin and Myosin
Intermediate filaments is a ropelike polymers of
desmin and vimentin
Connects with the actin and the tubules, maintaining platelet shape
Intermediate Filament
Stains medium-gray in osmium-dye transmission electron microscopy preparations.
Alpha Granules
Alpha granules fuse with ______ in activated platelets
Surface-Connected Canalicular System
Appears later than alpha granules
Dense granules
Stain black (opaque) when treated with osmium in transmission electron microscopy
Dense Granules
Contents of Dense Granules
CAAS
- Calcium and Magnesium
- ADP
- ATP
- Serotonin
Are condensed remnant of the rough ER
Dense Tubular System (DTS)
“Control center” for platelet activation
Dense Tubular System (DTS)
Is the route of endocytosis and for secretion of alpha granule contents upon platelet activation
Surface Connecting Canalicular System (SCCS)
