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HEMATOLOGY 2 > Platelet ultrastructure > Flashcards

Platelet ultrastructure Flashcards

1
Q

Methods for studying platelet ultrastructure-

A

Scanning and transmission electron microscopy- flow cytometry- molecular sequencing

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2
Q

Platelet plasma membrane function-

A

Selectively permeable- supports platelet activation and plasma coagulation

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3
Q

Components anchored within the platelet membrane-

A

Glycoproteins and proteoglycans

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4
Q

Neutral phospholipids in platelet membrane-

A

Phosphatidylcholine and sphingomyelin (outer plasma layer)

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5
Q

Anionic phospholipids in platelet membrane-

A

Phosphatidylinositol- phosphatidylethanolamine- phosphatidylserine (inner cytoplasmic layer)

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6
Q

Role of phosphatidylinositol in platelets-

A

Supports platelet activation by supplying arachidonic acid

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7
Q

Phosphatidylserine function-

A

Flips to outer surface upon activation- provides charged surface for coagulation complexes

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8
Q

Coagulation complexes assembled on phosphatidylserine surface-

A

TENASE complex and PROTHROMBINASE complex

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9
Q

Glycocalyx function on platelet membrane-

A

Absorbs albumin- fibrinogen- and other plasma proteins through endocytosis

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10
Q

Ligand definition-

A

A molecule that binds to another molecule- especially a small molecule binding to a larger molecule

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11
Q

CAM definition-

A

Cell adhesion molecule

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12
Q

GP Ia/IIa receptor type: Integrin α2β1-

A

Binds collagen

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13
Q

GP Ia/IIa receptor type: Integrin αvβ1 receptor function-

A

Binds vitronectin

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14
Q

GP Ia/IIa receptor type: Integrin α5β1 receptor function-

A

Binds laminin

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15
Q

GP Ia/IIa receptor type: Integrin α6β1 receptor function-

A

Binds fibronectin

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16
Q

GP VI receptor type-

A

CAM of the immunoglobulin gene family

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17
Q

GP VI function-

A

Collagen receptor- triggers platelet activation

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18
Q

GP VI activation result-

A

Release of TXA2 and ADP

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19
Q

Effect of GP VI activation-

A

Increases avidity of integrins α2β1 and αIIbβ3

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20
Q

GP Ib/IX/V receptor type-

A

CAM of the leucine-rich repeat family

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21
Q

GP Ib/IX/V ligands-

A

VWF and thrombin bind GPIbα

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22
Q

Effect of thrombin on GP Ib/IX/V-

A

Thrombin cleaves a site on GP V

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23
Q

Bernard-Soulier syndrome cause-

A

Deficiency of GPIb/IX/V complex

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24
Q

GP Ibα function-

A

VWF-specific binding site

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25
Q

GP IIb/IIIa receptor type-

A

Integrin αIIbβ3

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26
Q

GP IIb/IIIa ligands-

A

Fibrinogen- VWF

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27
Q

GP IIb/IIIa function-

A

Key fibrinogen receptor

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28
Q

Glanzmann’s thrombasthenia cause-

A

Deficiency of GPIIb/IIIa

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29
Q

PAR 1- activates platelet; ligand:-

A

thrombin

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30
Q

PAR 4- activates platelet; ligand:-

A

thrombin

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31
Q

P2Y1- activates platelet; ligand:-

A

Adenosine diphosphate (ADP)

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32
Q

P2Y12- activates platelet; ligand:-

A

Adenosine diphosphate (ADP)

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33
Q

TPα and TPβ- activates platelet; ligand:-

A

Thromboxane A2 (TXA2)

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34
Q

α2-adrenergic- activates platelet; ligand:-

A

Epinephrine (Adrenaline)

35
Q

IP- inhibits platelet activation; ligand:-

A

Prostaglandin I2 (PGI2) [Prostacyclin]

36
Q

Platelet STR (Seven Transmembrane Repeat) Receptors-

A

PAR 1- PAR 4- P2Y1- P2Y12- TPα- TPβ- α2-adrenergic- IP

37
Q

Platelet membrane receptor for Low-affinity receptor for immunoglobulin Fc- involved in heparin-induced thrombocytopenia (HIT)-

A

FcIIA (CD32)

38
Q

Platelet membrane receptor for Integrin for platelet binding to endothelial cells- WBCs- and each other; found on α-granule membranes and surfaces of activated platelets; quantifiable by flow cytometry for in vivo platelet activation-

A

P-selectin (CD62)

39
Q

Platelet cytoskeleton components controlling shape change- extension of pseudopods- and secretion-

A

Microtubules- actin microfilaments- and intermediate microfilaments

40
Q

Microtubule formation-

A

Formed by tubulins

41
Q

Function of microtubules in platelets-

A

Maintain discoid shape- move inward on activation- support pseudopods

42
Q

Effect of cold temperature on platelets-

A

Microtubules disassemble- platelets become round

43
Q

Effect of warming to 37°C on platelets-

A

Microtubules reassemble- platelets recover discoid shape

44
Q

Function of microtubules during platelet activation-

A

Reassemble into parallel bundles to support rigidity of pseudopods

45
Q

Microfilament location-

A

Between microtubules and the membrane

46
Q

Microfilament formation-

A

Formed by actins

47
Q

Function of actin in platelets-

A

Anchors plasma membrane glycoproteins and proteoglycans- present throughout cytoplasm

48
Q

State of actin in resting platelets-

A

Globular and amorphous

49
Q

Effect of increased cytoplasmic calcium on actin-

A

Becomes filamentous and contractile

50
Q

Intermediate filaments in platelets-

A

Desmin and Vimentin- connect with actin and microtubules to maintain shape

51
Q

Platelet granules flow through-

A

SCCS for α-granules and lysosomes- plasma membrane for dense granules

52
Q

α-granules in each platelet-

A

50 to 80 granules

53
Q

Staining of α-granules-

A

Medium-gray (osmium-dye transmission electron microscopy preparations)

54
Q

Primary contents of α-granules-

A

Proteins that participate in secondary hemostasis (coagulation)

55
Q

α-granule activation process-

A

Membranes fuse with SCCS- contents flow to nearby environment

56
Q

Functions of α-granule contents in nearby environment-

A

Participate in platelet adhesion- aggregation- and support plasma coagulation

57
Q

Protein present in α-granules (not in cytoplasm)-

A

β-thromboglobulin- PF-4 (platelet factor-4)- HMWK- PAI-1 (plasminogen activator inhibitor-1)- Plasminogen- Protein C inhibitor- EGF- PGDF- TGF-b

58
Q

Protein from α-granules that inhibits heparin-

A

β-thromboglobulin- PF-4 (platelet factor-4)

59
Q

Proteins from α-granules that support mitosis of vascular fibroblasts and smooth muscle cells-

A

EGF (endothelial growth factor)- PDGF (platelet-derived growth factor)- TGF-β (transforming growth factor-β)

60
Q

Protein in α-granules and platelet cytoplasm-

A

Fibrinogen- Fibronectin- Albumin- Immunoglobulins- VWF- Thrombospondin- Factor V

61
Q

Protein in α-granule membrane-

A

P-selectin

62
Q

Proteins in α-granule membrane and plasma membrane-

A

GP IIb/IIIa- GP IV- GP Ib/IX/V

63
Q

Number of dense granules per platelet-

A

2 to 7

64
Q

Other name for dense granules-

A

Delta granules

65
Q

Appearance of dense granules in electron microscopy-

A

Stain black (opaque) with osmium

66
Q

Dense granule release upon platelet activation-

A

Contents released directly into plasma

67
Q

Function of dense granules-

A

Vasoconstrictors and platelet agonists that intensify primary hemostasis

68
Q

Definition of agonist-

A

A substance that initiates a response when combined with a receptor

69
Q

Components of dense granules (MPCHASE)-

A

ADP- ATP- Phosphate- Serotonin (5-HT)- Histamine- Ca2+- Mg2+- Epinephrine

70
Q

Supports neighboring platelet aggregation by binding to P2Y1 and P2Y12-

A

ADP

71
Q

Function unknown- but ATP release is detectable upon platelet activation-

A

ATP

72
Q

Vasoconstrictor that binds endothelial cells and platelet membranes-

A

Serotonin (5-HT)

73
Q

Divalent cations support platelet activation and coagulation-

A

Ca2+ and Mg2+

74
Q

Few in number- stain positive for arylsulfatase- β-glucuronidase- acid phosphatase- and catalase-

A

Lysosomes

75
Q

Flow through SCCS- digest vessel wall matrix components during in vivo aggregation-

A

Lysosomes

76
Q

Digest autophagic debris-

A

Lysosomes

77
Q

SCCS serves as the route for-

A

endocytosis- secretion of α-granule contents- secretion of lysosome contents

78
Q

Less developed in the SCCS and lacks some of the glycoprotein receptors present on the platelet surface-

A

Glycocalyx

79
Q

Plasma membrane invades platelet interior- producing-

A

SCCS

80
Q

Control center for platelet activation- closely aligned to the SCCS- condensed remnant of the rough endoplasmic reticulum- sequesters calcium and bears enzymes supporting platelet activation-

A

DTS (Dense Tubular System)

81
Q

DTS Enzymes supporting platelet activation-

A

phospholipase A2- cyclooxygenase- thromboxane synthetase- phospholipase C

82
Q

Enzymes that supports eicosanoid synthesis pathway producing thromboxane A2-

A

phospholipase A2- cyclooxygenase- thromboxane synthetase

83
Q

Enzymes that supports production of inositol triphosphate (IP3) and diacylglycerol (DAG)-

A

phospholipase C

84
Q

Most frequent anti-platelet drug- cyclooxygenase inhibitor-

A

Aspirin (acetylsalicylic acid)

HEMATOLOGY 2 (15 decks)

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