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Physiology > Hemostasis > Flashcards

Hemostasis Flashcards

0
Q

What are the factors in hemostasis?

A

-vascular constriction, platelet aggregation, clot formation, thrombin, clotting cascade, fibroblast invasion & ct. formation, clot dissolution, prevention of inappropriate clotting,

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1
Q

Hemostasis

A

the arrest of bleeding

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2
Q

Bleeding requires ____

A

break in vessel wall & pressure gradient

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3
Q

What are differences in bleeding types?

A
  • injury to microcirculation vs. large a.

- injury to large a. vs. v

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4
Q

What processes act to stop blood flow from damaged vessel?

A
  1. Vasoconstriction
  2. Platelet aggregation (plug)
  3. Blood clotting
  4. Fibrous tissue growth/clot dissolution
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5
Q

Mechanism of platelet plug fromation

A
  1. Break occurs
  2. ADP & thromboxane A2 released
  3. ADP/thromboxane A2 recruits more platelets & thromboxane A2/ADP
  4. Platelet aggregate to form plug
  5. ADP also interacts with intact endothelium to inhibit platelet aggregation there by stimulating the release of prostacyclin & NO.
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6
Q

Thromboxane A2 is a

A

vasoconstrictor

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7
Q

What limits platelet plug to the damaged area?

aka what inhibits platelet aggregation

A

Prostacyclin & NO release from normal endothelium

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8
Q

Major roles of aggregated platelet plug

A
  1. Seals break in vessel wall
  2. Actin-myosin complexes in platelets constrict to compact plug
  3. Additional vasoconstrictor release
  4. Releases chemicals that contribute to clotting cascade
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9
Q

vessel walls break in

A

capillaries all the time b/c they’re so fragile.

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10
Q

Clot formation is

A

the most powerful hemostatic mechanism

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11
Q

first defense against vessel break

A

platelet plug

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12
Q

second defense against platelet plug

A

clotting

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13
Q

Clot formation function

A

strengthen and support platelet plug.

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14
Q

Clotted blood

A

meshwork of fibrin that traps blood cells and serum

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15
Q

what activated clot formation

A

collagen fibers in the break.

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16
Q

What has to happen for clot formation to occur?

A

fibrinogen (solumbe) must convert to fibrin (insoluble compound)

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17
Q

Step 1 in clot formation

A

fibrinogen converts to fibrin with the help of Ca and thrombin

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18
Q

Fibrin’s job

A

creates clot’s threadlike structure

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19
Q

Prothrombin becomes thrombin by…

A

interacting with Ca and prothrombin activator

20
Q

What is absolutely needed for clot formation to even begin?

A

Calcium!

21
Q

Thrombin does what things?

Test Q

A
  1. Enhances prothrombin activation
  2. Enhances platelet aggregation (which leads to prothrombin release/activation)
  3. Activates Factor XIII which stabilized fibrin meshwork
  4. Stimulates conversion of fibrinogen to fibrin
22
Q

Clotting cascade’s 2 pathways

A

extrinsic and intrinsic

23
Q

Extrinsic clotting cascade pathway

A

clotting of blood that escaped into tissues.

24
Q

How does the extrinsic pathway begin?

A

traumatized tissue releases tissue thromboplastin which DIRECTLY activates factor X

25
Q

Intrinsic clotting cascade pathway

A

Factor XII activated by contact with collagen or foreign object

26
Q

Clot retration

A

after clot formation, trapped platelets contract, pulling damaged vessel walls closer

27
Q

Where do extrinsic and intrinsic clotting cascade pathways converge?

A

on Factor 10!

28
Q

Which clotting cascade pathway is faster?

A

extrinsic!

29
Q

What initiates the intrinsic clotting cascade pathway?

A

contact with inactive Factor XII (Hageman factor) which activates factor XII

30
Q

Fates of clot formation (2)

A
  1. Invasion by fibroblasts (causes scaring)

2. Dissolution of the clot

31
Q

Which clot formation fate is typical?

A

Invasion by fibroblasts

32
Q

What happens during an invasion by fibroblasts?

A

-Fibroblasts from connective tissue through the clot

33
Q

When does fibroblast invasion occur?

A

within hours after clot formation

34
Q

How long until there is complete organization into fibrous tissue?

A

within 1-2 weeks of clot formation

35
Q

Where does clot dissolution occur?

A

where clots are not needed

36
Q

How does clot dissolution occur?

A

The proteolytic enzyme plasmin digests fibrin fibers & other clotting factors

37
Q

Factor XII is involved in…

A
  1. Clot formation

2. Clot dissolution

38
Q

How does factor XII cause clot dissolution?

A

Plasmin is trapped in clot during formation and factor XII helps activate it

39
Q

What stimulates plasminogen to become plasmin?

A

factor XII and tissue plasminogen activator (tPA)

40
Q

Plasmin

A

fibrinolytic enzyme that dissolves clots

41
Q

Tissue plasminogen activator (tPA)

A

stimulates plasmin formation and plasminogen activation

42
Q

How is inappropriate clot formation prevented?

A

Tissue plasminogen activator (tPA) continuously converts plasminogen to plasmin so fibrin in blood doesn’t turn blood into a solid/gel.

ongoing low level of fibrin formation is countered by low level of fibrinolytic activity

43
Q

Conditions of excessive bleeding

A
  1. Hemophilia
  2. Platelet deficiency (thrombocytopenia)
  3. Vitamin K deficiency
44
Q

Hemophilia

A
  • caused by deficiency in a clotting cascade factor
  • common in males
  • mostly a genetic inability to make factor VIII
45
Q

platelet deficiency (thrombocytopenia)

A

leads to hundreds of small, confined hemorrhagic areas as blood leaks from sm. vessels before coagulation can occur.

46
Q

how long does it normally take platelet coagulation to occur?

A

1-2 min to start clotting and 6-10 min to complete it

47
Q

Vitamin K deficiency

A
  • leads to formation of structurally incomplete clotting factors which causes bad clotting.
  • -Warfarin (caumadin) = Vit. K antagonist

Physiology (10 decks)

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