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HEMA 2 LAB > 4-ADD PLATELET ULTRASTRUCTURE > Flashcards

4-ADD PLATELET ULTRASTRUCTURE Flashcards

1
Q

What is the color of platelets when stained with Romanowsky stain

A

Dense to purple

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2
Q

What are the four major areas seen in platelet electron microscopy

A

Peripheral Zone+Submembrane Area+Sol-Gel Zone+Organelle Zone

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3
Q

What comprises the platelet’s peripheral zone

A

Outer membrane and related structures

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4
Q

What area links the membrane and inner cell body in platelets

A

Submembrane Area

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5
Q

What constitutes the matrix/muscle and skeletal portion of platelets

A

Sol-Gel Zone

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6
Q

What zone consists of granules

A

dense bodies

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7
Q

What is the metabolic center of the platelet

A

Organelle Zone

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8
Q

What is the carbohydrate layer with a net negative charge on the platelet surface

A

Glycocalyx

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9
Q

What is the thickness of the glycocalyx

A

20-30 nm

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10
Q

What is the function of the glycocalyx

A

Absorption and transport of proteins via endocytosis

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11
Q

What are the predominant lipids in the platelet bilayer plasma membrane

A

Phospholipids and cholesterol

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12
Q

What is the main function of phospholipids in platelets

A

Support platelet activation (internally) and plasma coagulation (externally)

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13
Q

Which phospholipids predominate in the outer plasma layer

A

Phosphatidylcholine and sphingomyelin

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14
Q

Which phospholipids predominate in the inner cytoplasmic layer

A

Phosphatidylinositol

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15
Q

What are the functions of cholesterol in platelet membranes

A

Membrane stabilization+maintains fluidity+regulates transmembrane passage

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16
Q

What are the two forms of cholesterol present in platelet membranes

A

Esterified cholesterol and unesterified cholesterol

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17
Q

What do glycoproteins and proteoglycans support on the platelet surface

A

Glycosaminoglycans+oligosaccharides+glycolipids+glycosylated receptors

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18
Q

What is the sponge-like network within platelets

A

Surface-Connected Canalicular System (SCCS)

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19
Q

What are the functions of the SCCS

A

Storage of hemostatic proteins+enhanced platelet-environment interaction+increased access to platelet interior+increased egress of products

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20
Q

What is the condensed remnant of rough endoplasmic reticulum in platelets

A

Dense Tubular System (DTS)

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21
Q

What is the DTS’s primary function

A

Control center for platelet activation+Sequesters Ca2+

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22
Q

What enzymes are present in the DTS

A

Phospholipase A2+Cyclooxygenase+Thromboxane synthetase

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23
Q

What maintains the platelet’s discoid shape and facilitates alpha-granule expression

A

Circumferential microtubules

24
Q

What happens to platelets at lower temperatures

A

Become round

25
At what temperature do platelets recover their discoid shape
37°C
26
What is the diameter of microtubules
25 nm
27
What are microtubules made of
8-20 tubules (composed of multiple subunits of tubulin)
28
What is the function of microfilaments (composed of actin)
Maintains platelet shape+controls pseudopod extension+controls granule secretion
29
What is the function of intermediate filaments (desmin and vimentin)
Maintains platelet shape+controls pseudopod extension+controls granule secretion
30
How many alpha granules are typically in one platelet
50-80 alpha granules
31
Name some coagulation proteins found in platelet alpha granules
Fibrinogen+Factor V+HMWK+PAI-1+Plasminogen
32
Name some noncoagulation proteins found in platelet alpha granules
Thrombospondin+Multimerin+Protein C inhibitor+VEGF/VPF
33
Name some proteins present in both platelet cytoplasm and alpha granules
Fibronectin+Immunoglobulins+Albumin
34
Name some proteins restricted to the alpha granule membrane
P-selectin+GMP33
35
Name some proteins present in both alpha granules and the plasma membrane
GP IIb/IIIa+GP IV+GP Ib/IX/V+PECAM-1+cap1+CD9
36
What anchors plasma membrane glycoproteins and proteoglycans
Actin
37
What percentage of platelet cytoplasm consists of actin
20%-30%
38
What is the state of actin in resting platelets
Globular and amorphous
39
What is the state of actin in activated platelets
Filamentous and contractile (as calcium increases)
40
Name the small molecules found in platelet dense granules
ADP+ATP+Serotonin+Ca2++Mg2+
41
What is the function of ADP in platelet dense granules
Supports neighboring platelet aggregation (P2Y1/P2Y12 receptors)
42
What is the function of ATP in platelet dense granules
Unknown; ATP release detectable on platelet activation
43
What is the function of serotonin in platelet dense granules
Vasoconstrictor+binds endothelial cells/platelet membranes
44
What is the function of Ca2+ and Mg2+ in platelet dense granules
Support platelet activation and coagulation
45
What is the diameter of lysosomes
300 nm
46
Name some contents of lysosomes
Arylsulfatase+β-glucuronidase+acid phosphatase+catalase
47
What are the functions of lysosomes
Digest vessel wall matrix components during in vivo aggregation+digest debris
48
What ligands does GP Ia/IIa (integrin α2β1) bind
Collagen
49
What ligand does GP VI (CAM of immunoglobulin family) bind
Collagen
50
What is the function of GP VI
Key collagen receptor+triggers activation/agonist release to increase integrin avidity
51
What ligands does GP IV bind
Collagen
52
What ligands does GP Ib/IX/V (CAM of leucine-rich repeat family) bind
VWF and thrombin
53
What is the structure of GP Ib/IX/V
2:2:2:1 complex of GP Ibα+Ibβ+GP IX+GP V
54
What is the VWF-specific site in GP Ib/IX/V
GP Ibα
55
What ligand does GP IIb/IIIa (integrin αIIbβ3) bind
Fibrinogen
56
Where is GP IIb/IIIa distributed
Surface membrane+SCCS+α-granule membranes
57
When does GP IIb/IIIa heterodimer form
On activation

HEMA 2 LAB (7 decks)

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