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MABS Physiology > Hemostasis and Blood Coagulation > Flashcards

Hemostasis and Blood Coagulation Flashcards

1
Q

what are the functions of the coagulation system?

A

rapid formation of mechanically sound clot

prevent clot formation at noninjured sites

gradual replacement of clot with viable tissue

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2
Q

relate the following action from the coagulation system with the desired result:

rapid formation of mechanically sound clot

A

Stop bleeding quickly

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3
Q

relate the following action from the coagulation system with the desired result:

prevent clot formation at noninjured sites

A

prevent thrombosis

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4
Q

relate the following action from the coagulation system with the desired result:

gradual replacement of clot with viable tissue

A

wound healing

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5
Q

what are the 3 steps of Hemostasis?

A

step 1: vascular spasm

step 2: platelet plug formation

step 3: coagulation

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6
Q

describe step 1: vascular spasm of hemostasis?

A

1) Reflex contraction of smooth muscle in the wall of small blood vessels (alpha 1 receptors on smooth muscle)
2) Reaction to injury – spasm Reduces diameter and cuts flow almost instantly

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7
Q

describe step 2: platelet plug formation of hemostasis?

A

Smooth vessel walls do not attract platelets (Blood vessels & platelets both positively charged so repulsion occurs)

Rough surfaces cause platelet adhesion

Once attracted, they release serotonin (enhance the vascular spasm), also, ADP, Thromboxane A2 (NSAIDS for clotting issues)

Within one minute this step occurs : Platelet plug will stop very minor “leaks”

If a severe cut, we move to step 3

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8
Q

describe step 3: coagulation of hemostasis?

A

complex of 20 substances

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9
Q

what step of the hemostasis process is occurring when:

Platelets stick to exposed collagen underlying damaged endothelial cells in vessel wall?

A

step 1

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10
Q

what step of the hemostasis process is occurring when:

Release Thromboxane A2, Serotonin & ADP activating other platelets:

Serotonin& Thromboxane A2 are vasoconstrictors decreasing blood flow through the injured vessel.

ADP causes stickiness

A

step 2

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11
Q

what step of the hemostasis process is occurring when:

Activated platelets stick together and activate new platelets to form a mass called a platelet plug

Plug reinforced by fibrin threads formed
during clotting process

A

step 3

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12
Q

what are two components important in blood coagulation?

A

platelet plug and fibrin clot

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13
Q

what do platelets do?

A

Stick to damaged blood vessels
requires von Willebrand factor

Spread out to cover damaged area

Activate and release contents
partly blocked by aspirin

Aggregate

Cause blood vessel constriction

Cause retraction of clot to draw wound edges together

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14
Q

in terms of what platelets do, the fact that platelets stick to damaged blood vessels requires this kind of factor?

A

von Willebrand factor

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15
Q

in terms of what platelets do, activation and release of contents are partly blocked by?

A

aspirin

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16
Q

*what is unique about von Willebrand factor?

A

shaped as a globular protein in its inactive form and unfolds under shear stress as an extended chain to keep platelets in the area to cover affected area by releasing glycoprotein receptors:

GP IIb/IIIa: Binds fibrinogen, allows platelets to aggregate with each other

the platelets contain an ALPHA GRANULE that holds the vWF, calcium that helps with adhesion and smooth muscle contraction, and glycoprotein receptors(inside platelet) :

GP Ib/IXa: Binds von Willebrand Factor (vWF), allows platelets to adhere to subendothelial tissue

17
Q

T/F, fibrin clot formation is a tightly controlled process?

A

T

18
Q

what initiates fibrin clot formation?

A

tissue factor and this forms a hemostatic envelope if clot is not enough

Not normally found on endothelial cells lining blood vessels, or on circulating blood cells

19
Q

what is significant about Hemostasis-step 3: Coagulation & Clot Stabilization?

A

it is a cascade of events for clot formation

once collagen is available, factor 12 is activated, it will activate 11, then 9, it sends an activator to activate factor 10 it is at this point that intrinsic and extrinsic pathways combine and the difference is what initiates each pathway:

intrinsic: collagen
extrinsic: tissue factor III

the extrinsic pathway is activated when tissue factor III is present which activates factor VII and this combines at level of factor 10

once both pathways meet at factor 10, it becomes a common pathway (at the same time the coagulation system is active at the site and proximal) and converts prothrombin to thrombin which changes fibrinogen to fibrin. Note that factor 13 is activated by thrombin to change fibrin into a mesh like cross linked fibrin (clot for wound)

20
Q

what is significant about factor 8?

A

it combines factor 9 and 7 together so that 10 can become activated so that 10 can become activated

21
Q

in fibrin clot formation, tissue damage exposes blood to _____?

A

tissue factor

22
Q

in fibrin clot formation, the coagulation cascade: series of enzymatic reactions lead to ____ formation?

A

thrombin

23
Q

in fibrin clot formation, what does thrombin convert fibrinogen into?

A

fibrin

24
Q

after fibrin polymerizes, what does it become?

A

crosslinked

25
Q

in fibrinolysis, degradation of fibrin clot is carried out by the enzyme called _____?

A

plasmin, which is necessary to remove to clot so wound healing can proceed

26
Q

in fibrinolysis, these are from blood vessels and other cells convert plasminogen to plasmin to begin the process

A

plasminogen activators

27
Q

how does thrombosis inactivation occur?

A

antithrombin III binds to a heparin like molecule and inactivates thrombin and factors 10a and 9a

28
Q

in terms of thrombosis inactivation, what is the tissue factor pathway inhibitor?

A

small molecules that work on factors 7a and 10a

29
Q

in terms of thrombosis inactivation, what is protein C in the coagulation cascade?

A

after thrombin is made by coagulation cascade, protein C is activated and lysis activated factors 5a and 8a

30
Q

in terms of thrombosis inactivation, what is t-PA in the coagulation cascade

A

aids in the fibrinolytic cascade

31
Q

in terms of clotting, how is Vitamin K needed?

A

for production of several clotting proteins

Fat-soluble vitamin present in many foods

Some made by bacteria in gut

Necessary for synthesis of several components of coagulation cascade (Factors II, VII, IX, and X)

Deficiency may lead to low levels of clotting factors, causing a bleeding tendency

Warfarin (Coumadin™): a drug that interferes with vitamin K action
used as an anticoagulant (prevent thrombosis)

32
Q

Vitamin K is necessary for synthesis of several components of coagulation cascade, what are they?

A

Factors II, VII, IX, and X

33
Q

a drug that interferes with vitamin K action

used as an anticoagulant (prevent thrombosis)

A

Warfarin (Coumadin)

34
Q

vitamin K is necessary for the binding of these molecules in the production of thrombin?

A

enzyme, proenzyme, helper to phospholipid membrane

35
Q

what do we mean when say the regulation of coagulation? what are the important molecules that are a part of this? what happens when there is a deficiency of these?

A

confines clot to injured area and helps prevent thrombosis; antithrombin, protein C, protein S

Deficiency of any of these proteins can increase risk of thrombosis causes clotting issues not being made at the proper rate

36
Q

what is antithrombin?

A

inhibits thrombin and other enzymes

37
Q

what is protein C?

A

degrades activated factors V and VIII

38
Q

what is protein S?

A

cofactor for protein C

39
Q

what are drugs that interfere with clotting?

A

aspirin- Often recommended for those over 50, reduces stickiness of platelets.

coumadin- Maintenance for those prone to clotting – and in atrial fibrillation

plavix– Newer – maintenance drug

heparin– Used in IV lines and blood collection

Typically suspend these before surgery

MABS Physiology (57 decks)

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