7. Haemostasis Flashcards

1
Q

importance of haemostasis

A

important survival mech to minimise blood loss after injury

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2
Q

5 main components of haemostasis

A
  • blood vessels
  • platelets
  • coagulation factors
  • coagulation inhibitors
  • fibrinolysis
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3
Q

2 forms of haemostatic plug

A

primary plug
stable plug (w/fibrin crosslinks)

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4
Q

endothelial cell effects of haemostasis

A
  • inhibit = release prostacyclin and nitric oxide
  • promote = source of vwf and tPA
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5
Q

initial reflex to minimise blood loos

A

vsaoconstriciton of smooth muscle cells
= until other mechanisms take overq

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6
Q

what are platelets

A

fragmentations of megakaryocyte cytoplasm
(1 megakaryo = 4000 platelts0

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7
Q

size of platelets

A

2-4 micrometers

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8
Q

lifespan of platelet

A

9-10days

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9
Q

nromal platelet count

A

150-400 x10^$

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10
Q

where are platelets destroyed and by which cells

A

spleen and liver
as per usual
by
Kupffer cells

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11
Q

process of making platelets name

A

endomitotic synchronous nuclear replication

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12
Q

3 things that control platelet production

A
  • neg feedback from number of circ platelets
  • stim by thrombopoietin
  • IL-3 and GM-CSF = general growth factors
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13
Q

what is glycocalyx and what is it primarily composed of

A

outer layer of cell
glycoproteins

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14
Q

which glycoproteins are in platelet glycocalyx

A

GPIa
GPIb
GPIIb

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15
Q

function of platelet glycocalyx

A

when collagen exposed
glycoproteins allow platelet to adgere onto area of damage

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16
Q

what is the enrgy reserve in a platelet

A

glycogen

17
Q

what is the dense tubular system in platelet for

A

site of prstaglandin and thromboxan A2 synthesis

18
Q

what is platelet contractile proteins

A

the submembranous filaments
makes platelet aggregation irreversible

19
Q

what are the 2 types of granules in a platelet

A

electron dense
and
alpha granules

20
Q

what do electron dense grnaules contain

A

Ca2+
ADP and ATP (enhance platelet adhesion)
Serotonin (vasocontriction)

21
Q

what do alpha granules contain

A
  • platelet derived growth factor
  • platelet factor 4
  • fibrinogen
  • vWF
  • factor V and VIII
22
Q

what does platelet factor 4 do

A

Factor 4 moderates effects of Heparin - promotes its anticoagulant activity

23
Q

what is the open canalicular system

A

an internal membrane structure found in platelets
allows release of the granules

24
Q

3 steps of forming the platelet plug

A

adhesion/activation
secretion (of granules)
aggregation

25
Q

formation of platelet plug

A
  • plasma vWF released from endo cells
    = allows indirect adhesion between platelets and damaged surface
  • GPIIa and b are paired
  • all the GPs work together to make strong adhesion between platelet and damaged surface
  • then platelets will aggregate
26
Q
A