Platelet Ultrastructure (P) Flashcards
What are the different zones of platelet ultrastructure?
1) Peripheral zone
2) Sol-gel zone
3) Organelle zone
4) Membranous zone
What are the components of peripheral zone?
It contains glycoproteins
What are the components of sol-gel zone?
It contains microtubules and microfilaments
What are the components of organelle zone?
It contains platelet granules
What are the components of membranous zone?
It contains membrane systems
What are the components of resting plasma membrane?
1) Predominant lipids
2) Outer, blood plasma layer
3) Inner, cytoplasmic layer
4) Glycoproteins and proteoglycans
5) Glycocalyx
What are the component of predominant lipids?
1) Phospholipids
2) Cholesterol
What is the function of cholesterol?
It stabilizes the membrane and maintains fluidity
What are the components of outer, blood plasma layer?
1) Phosphatidylcholine
2) Sphingomyelin
What are the components of inner, cytoplasmic layer?
1) Phosphatidylinositol
2) Phosphatidylethanolamine
3) Phosphatidylserine
What is the purpose of phosphatidylinositol?
It supplies arachidonic acid
What is the purpose of glycoproteins and proteoglycans?
These responds to ligands or agonists
What is glycocalyx?
1) It is the surface of PLT membrane
2) Adhesive and absorbs albumin, fibrinogen, and other plasma proteins
What is the purpose of cytoskeleton?
1) Control PLT shape change
2) Extends pseudopods
3) Secretes granule contents
What are the components of cytoskeleton?
1) Circumferential microtubules
2) Meshwork of filaments
3) Intermediate microfilaments
What are the characteristics of circumferential microtubules?
Resides beneath the plasma membrane
What are the functions of circumferential microtubules?
1) Maintains the discoid shape of PLT
2) Provide rigidity to pseudopods
3) Express alpha (insert sign)-granule contents during PLT activation
What are the characteristics of meshwork of microfilaments?
1) Resides between plasma membrane and microtubules
2) Composed of actin which allows the PLT to contract
What is the purpose of intermediate microfilaments?
Maintains PLT shape
What are the 2 components of intermediate microfilaments?
1) Desmin
2) Vimentin
What is the function of desmin and vimentin?
To connect tubules to membrane
What are alpha (insert sign)-granules?
1) 50-80 granules per PLT
2) Fuse with SCCS to release their contents
3) Stain medium gray in osmium dye-TEM
What are dense granules?
1) 2-7 per PLT
2) No membrane system used; release contents directly to plasma
3) Stain black opaque in osmium dye-TEM
What is the function of lysosomes?
To digest autophagic debris
Lysosomes stain positive for what?
Lysosomes stain (+) for arylsulfatase, beta (insert sign)- glucoronidase, acid phosphatase, and catalase
What are the 2 types of system under membrane system?
1) Surface-Connected Canalicular System
2) Dense Tubular System
What is the meaning of SCCS?
Surface-Connected Canalicular System
What is SCCS?
1) Sponge-like
2) Enables PLT to store additional proteins
3) Route for endocytosis
4) Secretion of alpha-granule contents
What is the meaning of DTS?
Dense Tubular system
What is DTS?
1) A condensed RER remnant
2) Sequesters ^Ca2+
3) Holds a number of PLT activation enzymes
