Trans - Hemostasis

Question 1

hemostasis - define

Answer 1

process which spontaneously arrests flow of blood from vessels carrying blood under pressure - control unwanted blood flow

Question 2

3 components of hemostasis

Answer 2

1. vasoconstriction
2. adhesion and aggregation of formed elements
3. blood coagulation

Question 3

blood coagulation - define

Answer 3

process resulting in formation of insoluble fibrin clot from fibrinogen in plasma

Question 4

blood coagulation is determined by:

Answer 4

procoagulant and anticoagulant factors

Question 5

problem of blood coagulation

Answer 5

may lead to obstruction of normal blood flow

Question 6

fibrinolysis - define

Answer 6

degradation of fibrin clot

Question 7

final common pathway

Answer 7

1. factor Xa converts prothrombin to thrombin
2. thrombin converts fibrinogen to fibrin and factor XIII to factor XIIIa
3. factor XIIIa stabilizes fibrin

Question 8

how does factor XIIIa stabilize fibrin?

Answer 8

by catalyzing formation of covalent cross links

Question 9

intrinsic pathway - how is it activated

Answer 9

when collagen comes into contact with plasminogen following endothelial damage

Question 10

intrinsic pathway

Answer 10

1. damaged surface stimulates kininogen and kallikrein
2. kininogen and kallikrein converts XII to XIIa
3. XIIa converts XI to XIa
4. XIa converts IX to IXa
5. IXa and VIIIa converts X to Xa
6. Xa leads to final common pathway

Question 11

extrinsic pathway - how is it activated

Answer 11

activated by a tissue factor released by damaged tissues in response to trauma

Question 12

what tissue factor activates the extrinsic factor

Answer 12

tissue thromboplastin

Question 13

extrinsic pathway

Answer 13

1. trauma induces a change from VII to VIIa
2. VIIa contributes to release of tissue thromboplastin from blood vessels
3. tissue thromboplastin converts X to Xa
4. Xa leads to final common pathway

Question 14

TPA - function

Answer 14

tissue plasminogen factor, converts plasminogen to plasmin

Question 15

[T/F] TPA acts on all plasminogen

Answer 15

F, it only acts on plaminogen physically associated with fibirin

Question 16

thrombus - define

Answer 16

blood clot formed within intravascular space during life

Question 17

thrombus - may lead to:

Answer 17

1. ischemia

2. infarction

Question 18

ischemia - define

Answer 18

hypoperfusion of tissues

Question 19

infarction - define

Answer 19

necrosis of tissue due to prolonged ischemia

Question 20

a thrombus may fragment to yield:

Answer 20

thromboembolus

Question 21

embolus - define

Answer 21

portion of material distinct from blood and carried by bloodstream from one site of the body to another

Question 22

virchow’s triad

Answer 22

predisoposing factors to coagulation

1. stasis - sluggish blood flow
2. altered endothelial surface due to damage or injury
3. hypercoagulability of blood

Question 23

virchow’s triad - stasis may be caused by:

Answer 23

hyperviscosity, as in polycythemia

Question 24

polycythemia - define

Answer 24

presence of high amount of RBCs in blood, may cause hyperviscosity

Question 25

virchow's triad - hypercoagulability may be caused by:

Answer 25

imbalance of coagulant and anticoagulant factors

Question 26

administration of TPA is most useful when:

Answer 26

when it is given before fibrin cross links are formed

Question 27

heparin - mechanism of action

Answer 27

1. binds plasma protein antithrombin, inducing conformational change that enhances inhibitory effect against thrombin and Xa 2. also binds thrombin, bringing it into close proximity with antithrombin

Question 28

heparin interferes with what pathway?

Answer 28

final common pathway

Question 29

heparin - how to administer

Answer 29

intravenously for rapid anticoagulatin

Question 30

[T/F] heparin is for long-term anticoagulation

Answer 30

F

Question 31

[T/F] warfarin is for long-term anticoagulation

Answer 31

T

Question 32

warfarin - how to administer

Answer 32

orally for long-term anticoagulation

Question 33

4 vitamin K dependent anticoagulant factors

Answer 33

9, 10, 7, 2

Question 34

warfarin - mechanism of action

Answer 34

1. vitamin K antagonist - blocks synthesis of vitamin-K dependent factors 2. inhibits posttranslational conversion of glutamate to gamma-carboxyglutamate (for calcium-mediated binding to membrane surfaces)

Question 35

treatment of warfarin toxicity

Answer 35

1. fresh frozen plasma - replenishment of clotting factors (short term) 2. vitamin k - restores capacity for synthesis of clotting factors (long term)

Question 36

gamma-carboxyglutamate - significance

Answer 36

1. uncommon modification of amino acids found in some functional clotting factors (e.g. vitamin-K dependent factors) 2. induces affinity for calcium ions