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hema - platelets Flashcards

1
Q

___ are directly produced from the megakaryocyte cytoplasm

A

platelets

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2
Q

As the megakaryocyte _____, clusters of granules aggregates to form _____

A

matures ; platelets

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3
Q

platelet development occurs via ______

A

endomitosis

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4
Q

NUCLEAR DIVISION WITHOUT CYTOPLASMIC DIVISION

A

endomitosis

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5
Q

A single megakaryoblast nucleus may contain ___ to ___ times the normal number of chromosomes

A

2 to 64

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6
Q

______ is densely staining, dispersed early and more compact at later stages

A

nuclear chromatin

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7
Q

______ are small at all development stages

A

nucleoli

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8
Q

Each Megakaryocyte produces ____ to _____ platelets

A

2,000 to 4,000

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9
Q

Most megakaryocytes at any stage of maturation and their precursors (megakaryoblasts) normally are found ONLY IN THE _______, not in the ______

A

BONE MARROW ; peripheral blood

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10
Q

Normal bone marrow contains approximately ______ megakaryocyte ( ____ megakaryocytes per 10x power field)

A

15 million ; 5-10

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11
Q

Megakaryocyte proliferation is largely regulated by ______

A

THROMBOPOIETIN

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12
Q

Additional growth factors including _____, _____, ____ support megakaryocytic development in the presence of thrombopoietin

A

kit-ligand, IL-3, IL-11

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13
Q

Serum thrombopoietin levels are inversely proportional to platelet count, however levels are increased in ________

A

liver disease and inflammation

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14
Q

Maturation sequence of megakaryoblast takes about ____ days

A

5

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15
Q

the more nuclear lobes the megakaryocyte possess, the _____ the cytoplasmic mass & therefore the more ____ produced.

A

larger ; platelets

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16
Q

Conversely megakaryocytes w/ lower _____ values produce larger platelets that are denser & more functionally active.

A

ploidy

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17
Q

increased production of platelets may be accomplished by means of 3 possible mechanisms:

A
  1. the no. of megakaryocytes in the BM may increase
  2. the size of the megakaryocytes may increase
  3. there may be a decrease in the maturation time of the megakaryocyte
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18
Q

major platelet production takes place in the _____, where the megakaryocytes make up less than 1% of the _______.

A

bone marrow ; nucleated cells of the marrow

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19
Q

thrombocytopoiesis occurs in _____

A

bone marrow

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20
Q

thrombocytopoiesis life span

A

5-9 days

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21
Q

platelet size

A

1-4 um or 2-4 um

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22
Q

platelet cytoplasm

A

light blue-purple and very granular

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23
Q

granular and located centrally

A

chromomere

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24
Q

surrounds the chromomere, nongranular and clear to light blue

A

hyalomere

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25
Q

Platelets are removed by ____ in the liver and spleen or by active use in _____

A

macrophage ; daily coagulation mechanisms

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26
Q

Circulating platelets are distributed between the spleen and blood.. ____ in spleen and ____ in blood

A

1/3 are always in the spleen and 2/3 are in peripheral blood

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27
Q

What is the platelet value in splenectomy?

A

platelet count is higher w/o a slpeen (undergone splenectomy)

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28
Q

What is the platelet value in splenomegaly?

A

platelet count is lower in splenomegaly

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29
Q

first stage of platelet maturation

A

megakaryoblast

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30
Q

the second stage of platelet maturation

A

promegakaryocyte

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31
Q

the third stage of platelet maturation

A

granular megakaryocyte

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32
Q

the fourth stage of platelet maturation

A

mature megakaryocyte

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32
Q

size of megakaryoblast

A

20-50 um (earliest recognizable)

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33
Q

size of promegakaryocyte

A

20-60 um

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34
Q

size of granular megakaryocyte

A

30-90 um

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35
Q

size of mature megakaryocyte

A

40-120um (largest cell in the bone marrow)

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36
Q

M: Round oval, or may be kidney shaped
C: Fine
Nucleoli: Multiple nucleoli
Nuclei: –
color: Deeply basophilic (blue)
Usually darker than myeloblast
Amount: small - moderate
Granules: Nongranular or rare
N/C: 10:1 (high)

A

Megakaryoblast (Stage I)

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37
Q

M: Irregular in shape maybe horseshoe shaped
C: Coarse
Nucleoli: Multiple nucleoli
Nuclei: –
color: Less basophilic
Amount: more abundant
Granules: Granules begin to form in the golgi region
N/C: 4:1-7:1 (high)

A

Promegakaryocyte (Stage II)

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38
Q

M: Smaller size
C: Coarser than stage II
Nucleoli: No nucleoli visible
Nuclei: Multiple nuclei visible
color: pinkish
amount: abundant
granules: Very fine & diffusely granular
N/C: 2:1-1:1 (low)

A

Granular Megakaryocyte (Stage III)

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39
Q

M: multilobulated
C: Coarse and linear
Nucleoli: No nucleoli visible
Nuclei: Multiple nuclei present or nucleus is multilobulated
Color: Totally pink
Amount: abundant
Granules: Coarse clumps of granules aggregating into little bundles, which bud off from the periphery to become platelets
N/C: Less than 1:1 (low)

A

Mature Megakaryocyte (Stage IV)

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40
Q

ULTRASTRUCTURE OF PLATELET

A
  1. peripheral zone
  2. sol-gel zone
  3. organelle zone
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41
Q

consists 30 or more glycoproteins, phospholipids & platelet VIII:vWF

A

plasma membrane

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42
Q

receptor for von Willebrand’s factor (vWF)

A

Glycoprotein lb

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43
Q

receptor for fibrinogen

A

Glycoprotein llb/llla

44
Q

receptor for thrombin

A

Glycoprotein Va

45
Q

lies directly beneath the platelet membrane

A

sol-gel zone

46
Q

sol-gel zone is composed of _____ & ______

A

microfilaments & microtubules

47
Q

maintain platelet shape & a contractile system

A

cytoskeleton

48
Q

contain the proteins actin & myosin w/c, upon stimulation of the platelet, will interact to actomyosin (thrombosthenin)

A

Microfilaments

49
Q

contractile protein important in clot retraction

A

actomyosin (thrombosthenin)

50
Q

composed of the protein tubulin, w/c maintains the platelet’s disc shape.

A

microtubules

51
Q

composed of the mitochondria, alpha granules, dense bodies & lysosomal type granule.

A

Organelle Zone

52
Q

are the most numerous & contain a no. of substances including platelet factor 4, ß- thromboglobulin, platelet derived growth factor (PDGF), thrombospodin, von Willebrand factor, fibrinogen, fibrinectin & platelet albumin.

A

alpha granules

53
Q

Ca, ADP, Serotonin (5-hydroxytryptamine) of organelle zone

A

dense granules

54
Q

for energy production

A

mitochondria

55
Q

What are the 2 membranous systems?

A

dense tubular system
open canalicular system

56
Q
  • serves as the site of Arachidonic acid metabolism
  • Also functions as a Calcium-sequestering pump that maintains platelet cytoplasmic Ca levels
  • It also synthesizes prostaglandin.
  • The surface connecting system, as an invagination of the plasma membrane, acts as a canal for the release of the granule constituents & cytoplasm to the exterior of the platelet.
  • It also involved in platelet phagocytosis.
A

Dense tubular system

57
Q
  • release of granules
  • Provides direct communication between intracellular and extracellular compartments
A

Open canalicular system

58
Q
  • originates from MK ER
  • composed of channels located near OCS
A

Dense Tubular System

59
Q

Dense Tubular System is a site of

A
  • Ca2+ storage
  • several enzymes, ATPases, Cyclooxygenase (PG synthesis)
60
Q

Ca2+ storage is important for ____

A

triggering contraction of actinomysin

61
Q

platelet function: hemostasis and thrombosis

A

adhesion
activation
spreading
secretion
aggregation
procoagulant activity
clot retraction
tissue repair

62
Q

platelet function: maintenance/regulation of vascular tone

A

uptake of serotonin when resting
release of serotonin, thromboxane, prostaglandins upon activation

63
Q

platelet function: inflammation

A

atherosclerosis
allergic asthma
renal disease
chemotaxis

64
Q

platelet function: host defense

A

phagocytosis/internalisation of viruses and bacteria
killing of bacteria
release of platelet microbicidal proteins
superoxide production

65
Q

platelet function: tumour biology

A

tumour growth
tumour killing
tumour metastasis

66
Q

what substances promote coagulation

A

HMWK, Fibrinogen, Factor V, Factor VIII :vWF

67
Q

the source of the substances: HMWK, Fibrinogen, Factor V, Factor VIII :vWF

A

alpha granules

68
Q

principal/function of HMWK

A

Contact activation of intrinsic coagulation pathway

69
Q

principal/function of fibrinogen

A

Converted to fibrin clot

70
Q

principal/function of Factor V

A

cofactor in fibrin clot formation

71
Q

principal/function of HMWK Factor VIII :vWF

A

Assists platelet adhesion to subendoethelium to provide coagulation surface

72
Q

what substances promote aggregation

A

ADP, Calcium, Platelet Factor 4, Thrombospondin

73
Q

sour of substances ADP and Calcium

A

Dense Bodies

74
Q

source of substances Platelet Factor 4 and Thrombospondin

A

Alpha granules

75
Q

principal/function of ADP, Calcium, Platelet Factor 4, Thrombospondin

A

promote platelet aggregation

76
Q

what substances promote vasoconstriction

A

serotonin, Thromboxane A2 precursors

77
Q

source of serotonin

A

dense bodies

78
Q

source of thromoxane A2 precursors

A

membrane phospholipids

79
Q

principal/function of serotonin, Thromboxane A2 precursors

A

Promotes vasoconstriction at injury site

80
Q

what substance promote vascular repair

A

Platelet-derived growth factor
Beta thromboglobulin

81
Q

source of Platelet-derived growth factor and Beta thromboglobulin

A

Alpha granules

82
Q

principal/function of platelet-derived growth factor

A

Promotes smooth muscle growth for vessel repair

83
Q

principal/function of beta thromboglobulin

A

Chemotactic for fibroblasts to help in vessel repair

84
Q

other systems affected

A

Plasminogen, α2- antiplasmin, C1 esterase inhibitor

85
Q

source of Plasminogen, α2- antiplasmin, C1 esterase inhibitor

A

alpha granules

86
Q

principal/function of Plasminogen

A

Precursor to plasmin, which induces clot lysis

87
Q

principal/function of α2- antiplasmin

A

Plasmin inhibitor; inhibits clot lysis

88
Q

principal/function of C1 esterase inhibitor

A

Complement system inhibitor

89
Q

_________ must be sufficient for them to play their supportive role in hemostasis. When evaluating a bleeding problem that may be traceable to platelets, the counting of platelets is an important & logical starting point.

A

platelet numbers

90
Q

platelet count may be done simply by _______ on a peripheral blood film or by using various ___________.

A

estimating the no. of platelets ; manual or automated techniques

91
Q

a general reference range is ______

A

150-400x10^9/L

92
Q

there are approx. ________ in normal peripheral blood.

A

10-40 RBCs/platelet

93
Q

an oil immersion field containing 100 RBCs should have between _______, whereas a filed containing 200 RBCs should have between _______

A

3-10 platelets ; 5-20 platelets

94
Q

review of peripheral films is advantageous in ___________.

A

detecting causes of artifactually low counts secondary to platelet clumping caused by anticoagulant-dependent platelet agglutinins or clots from poorly collected specimens

95
Q

Giant platelets seen in some___________ will also be appreciated by this mtd.

A

congenital platelet defects & certain myeloproliferative disorders

96
Q

The accepted normal range of the platelet count is generally between _________ of blood, although values much lower than this can be quite adequate for ______.

A

150 to 400 X 10^9/L ; hemostasis

97
Q

Many clinicians will refrain from platelet repletion in a stable patient until counts drop below _______

A

10 to 20 X 10^9/L.

98
Q

Initial evaluation of the platelet count must take into consideration any ___________

A

pseudothrombocytopenia.

99
Q

often due to cold-reacting platelet agglutinins or platelet binding to neutrophils (platelet satellitism).

A

Pseudothrombocytopenia

100
Q

In Pseudothrombocytopenia, The agglutinins are often seen in patients with __________ and usually only bind platelets when calcium is _______, such as in an ______ blood collection tube.

A

high immunoglobulin levels or infections ; chelated ; EDTA

101
Q

A pseudothrombocytopenia associated with the ________ has also been reported.

A

glycoprotein IIb/IIIa antagonist drug abciximab

102
Q

________ is an indication of platelet size.

A

mean platelet volume (MPV)

103
Q

Normal MPV ranges are approximately _________

A

8 to 10 fL

104
Q

The MPV can be an indication of _________, because platelets newly released from the bone marrow are _____ and tend to ______ with age in the circulation.

A

platelet turnover ; larger ; decrease in size

105
Q

In patients with rapid turnover, the platelets will, in general, be _____ because of the ________.

A

larger ; larger size of newly produced platelets

106
Q

True ________ usually have uniformly large platelets; often the platelets are at least ______ the normal size and may be as large as ______.

A

congenital macrothrombocytopenias ; twice ; erythrocytes

107
Q

Newer techniques based on messenger RNA detection in platelets (reticulated platelets) may also be helpful to indicate the rate of _________.

A

thrombopoiesis

mt (54 decks)

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