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Bio 364 Exam 2 Ch. 19, 20, 21 > 19.5 hemostasis > Flashcards

19.5 hemostasis Flashcards

1
Q

define hemostasis

A

arresting or stopping of bleeding

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2
Q

in hemostasis a series of events helps prevent

A

excessive blood loss

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3
Q

what is the immediate response in a damaged blood vessel?

A

vascular spasm

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4
Q

describe vascular spasm

A

the immediate but temporary response to vascular damage, due to smooth muscle cntx in the wall

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5
Q

what type of stimulus will create a vascular spasm

A

upon tissue damage:
reflex
thromboxane released by platelets
endothelin released by endothelial cells

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6
Q

what are thromboxanes?

A

prostaglandin derived chemical released by platelets that trigger vascular spasm

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7
Q

what is endothelin?

A

a chemical released by endothelial cells that triggers vascular spasm

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8
Q

what is a platelet plug?

A

an accumulation of platelets that seals up small holes in vessels

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9
Q

what are the 3 steps of platelet plug formation

A

platelet adhesion
platelet release rxn
platelet aggregation

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10
Q

how does platelet adhesion occur in a platelet plug?

A

von Willebrand factor (a protein) is produced and secreted by the damaged endothelial cells and connects the exposed collagen to the platelets

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11
Q

what is vWF (von Willebrand factor)?

A

a protein secreted by the endothelial cells that connects the exposed collagen to the platelets

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12
Q

describe the positive feedback mechanism of platelet release rxn

A

adhered platelets release ADP, thromboxanes and other chemicals that activate more platelets to join the plug, which in turn release the same chemicals to recruit even more platelets

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13
Q

in which step of platelet plug formation is vWF released by endothelial cells?

A

step 1, platelet adhesion

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14
Q

in which step of platelet plug formation do platelets release ADP, thromboxanes and other chemicals?

A

step 2, platelet release rxn

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15
Q

describe platelet aggregation in platelet plug formation

A

activated platelets express surface receptors to which fibrinogen can bind
fibrinogen binds to these surface receptors and forms a bridge between other activated platelets and a platelet plug is formed

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16
Q

what chemicals do platelets release once a plug is formed?

A

phospholipids (platelet factor III)
coagulation factor V
both important in clot formation

17
Q

what factors in coagulation are already in the blood stream?

A

prothrombin

fibrinogen

18
Q

what enzyme is used to change prothrombin to thrombin?

A

prothrobinase

19
Q

what does thrombin do?

A

changes fibrinogen to fibrin

20
Q

what is fibrinogen?

A

a soluble plasma protein

21
Q

what does fibrin do?

A

forms the fibrous network of a clot

22
Q

what are the coagulation factors?

A

proteins found in plasma that circulate in their inactive state until the tissues are injured

23
Q

what produces changes that begin activation of the coagulation factors?

A

damaged tissues and platelets

24
Q

what are the 2 pathways to clot formation?

A

extrinsic and intrinsic

25
Q

what is a blood clot?

A

network of threadlike fibrin fibers, trapped blood cells, platelets and fluid

26
Q

define anticoagulants

A

they prevent coagulation factors from initiating clot formation
or
inhibit the processes that contribute to clote formation

27
Q

when does coagulation occur?

A

when coagulation factor concentrations exceed a certain threshold at the site of injury

28
Q

what are 3 anticoagulants?

A

antithrombin
heparin
prostacyclin

29
Q

what does antithrombin do and where is it produced?

A

produced by liver

slowly inactivates thrombin

30
Q

what does heparin do and where is it produced?

A

produced by basophils and endothelial cells

increases effectiveness of antithrombin

31
Q

what does prostacyclin do and where is it produced?

A

prostaglandin derivative from endothelial cells
causes vasodilation
inhibits release of coagulating factors from platelets?

32
Q

what inhibits release of coagulating factors from platelets?

A

prostacyclin

33
Q

what inactivates thrombin?

A

antithrombin

34
Q

what increases the effectiveness of antithrombin?

A

heparin

35
Q

what is clot retraction?

A

the condensing of the blood clot to become a denser, compact structure

36
Q

how does clot retration work?

A

platelets contain actin and myosin and attach to fibrin through processes
actin and myosin pull on the fibrinogen leading to clot retraction

37
Q

how is a clot dissolved?

A

plasmin (an enzyme that hydrolyzes fibrin)

Bio 364 Exam 2 Ch. 19, 20, 21 (19 decks)

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