Lecture 20: Hemostasis Flashcards

1
Q

4 steps of hemostasis?

A

1) Vascular spasm
2) Formation of a platelet plug
3) Formation of a blood clot
4) Repair of damage

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2
Q

What is hemostasis?

A

Steps taken by the body to limit blood loss

*Not confined only to the production of a blood clot!

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3
Q

Primary cause of vascular spasm?

A

Myogenic response to injury, no neurons or reflexes involved

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4
Q

Platelets release what that contributes to the vascular spasm?

A

Platelet factors

  • Serotonin
  • Thromboxane A2

*Both vasoconstrictors

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5
Q

What is a small component/contributor to vascular spasm, but is not necessary?

A

Neural reflex initiated by mechanical injury and pain

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6
Q

Purpose of vascular spasm?

A

Reduce blood loss by slowing/stopping blood flow out

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7
Q

Damage to vessel wall exposes?

A

Collagen

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8
Q

What will bind to exposed collagen?

A

Platelets

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9
Q

Step I of formation of platelet plug involves, its function?

A

Von Willebrand Factor (plasma protein) serves as anchor binding collagen and platelet (receptor)

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10
Q

What occurs during step II of formation of platelet plug?

A

Binding of platelet receptor (integrin) to collagen

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11
Q

What 2 things occur during activation of platelet bound to its receptor which has bound collagen?

A

1) Platelets swell

2) Extend podocytes

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12
Q

After the platelet swells what occurs?

A

Contraction

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13
Q

What does the platelet release after contraction?

A

Granules

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14
Q

What is found within granules that cause platelets to stick to vessel wall and eachother?

A

ADP and thromboxane A2

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15
Q

Platelet plug will stop what kind of bleeding?

A

Small breaks - nose, skin

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16
Q

3 major steps of clot formation?

A

1) Activation of prothrombin activator (Xa)
2) Activation of thrombin
3) Creation of fibrin from fibrinogen

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17
Q

What is clot retraction and function?

A
  • Get rid of excess fluid

- Solidify clot

18
Q

What is required for clot retraction?

A

Platelets

19
Q

Platelets express what for clot retraction, function?

A

Express Fibrin receptor, binds fibrin polymer together

20
Q

What pulls the fibrin together?

A

Platelets contain actin and myosin, which causes a contraction

21
Q

What do platelets secret for repair of damage?

A

Platelet-derived Growth Factor

22
Q

What does platelet-derived growth factor do?

A

Stimulates fibroblasts to grow into area

23
Q

Fibroblasts differentiate into?

A

Smooth muscle to close hole

24
Q

Where is plasminogen made?

A

Liver

25
Q

How is plasminogen activated?

A

Tissue plasminogen activator (tPA)

26
Q

Where does tPA come from?

A

Damaged tissue

27
Q

Activation of tPA is inhibited by?

A

tPA inhibitor which is always circulating in the blood

28
Q

What is found on an intact endothelial cell and is necessary for steps to produce plasmin?

A

Protein receptor called thrombomodulin

29
Q

Binding of thrombin to thrombomodulin causes?

A

Activation of Protein C, which is able to inactivate the t-PA inhibitor

30
Q

Inactivation of the t-PA inhibitor allows for?

A

Plasminogen (inactive) —-> Plasmin (active)

31
Q

Function of plasmin?

A

Lysis of fibrin (breaks down clot)

32
Q

What part of blood vessel prevents platelet from rupturing?

A

Smooth surface

33
Q

Function of glycocalyx?

A

Repels platelets

34
Q

Thrombomodulin changes activity of?

A

Thrombin

35
Q

How does fibrin limit clotting?

A

“Binds” thrombin and prevents it from working

36
Q

How does prostacyclin (PGI2) limit clotting?

A

Causes vasodilation and limits platelet aggregation

37
Q

How does Antithrombin III limit clotting?

A

When thrombin binds to it, works as an anticoagulant?

38
Q

Where is heparin derived from and how does it limit clotting?

A

Mast cells; increases antithrombin efficacy

39
Q

How does ProteinC limit clotting?

A

When activated, inactivates factors V and VII, which inhibits further fibrin creation

40
Q

Leidan mutation?

A

Protein C is unable to inactivate factor V

41
Q

Leidan mutation commonly seen in and becomes a problem when?

A

Usually women who will have multiple miscarriages