lec 7 : Function of Platelets & Mechanism of Hemostasis

Question 1

Formation of temporary platelet plug

Answer 1

Primary hemostasis

Question 2

Formation of definitive blood clot

Answer 2

Secondary hemostasis

Question 3

Factor I

Answer 3

Fibrinogen

Question 4

Factor II

Answer 4

Prothrombin

Question 5

Factor VIII

Answer 5

Antihemophilic factor A (globulin)

Question 6

Factor XIII

Answer 6

Fibrin-stabilizing factor

Question 7

Acts in a +ve feedback to facilitate its own formation through activation of factors VIII & V.

Answer 7

Thrombin

Question 8

Activates factor XIII

Answer 8

Thrombin

Question 9

Activates plasminogen to plasmin (anticlotting)

Answer 9

Thrombin

Question 10

Conversion of fibrinogen to fibrin.

Answer 10

Thrombin

Question 11

important Chemicals Affecting Platelet Aggregation

Answer 11

• Von Willebrand Factor (vWF)
• ADP
• Thromboxane A2
• Prostacyclin (PGI2)

Question 12

All clotting factors are globulins synthesized in liver

except

Answer 12

♦ Factor III (tissue thromboplastin)
♦ Factor IV (Ca++
)
♦ vWF (factor VIII related antigen)
♦ Factor XIII is synthesized by both liver & platelets

Question 13

Most clotting factors are ……………………………..which activate each other.

Answer 13

proteolytic enzymes

Question 14

•Factors ……….and………… act as cofactors but do not form a link in the chai

Answer 14

V and VIII

Question 15

The prothrombin activator is formed by the two clotting pathways

Answer 15

♣ The extrinsic pathway

♣ The intrinsic pathway

Question 16

Prothrombin Activator

Answer 16

Active factor X
PL (tissue or platelets)
Active factor V

Question 17

Extrinsic pathway is much more………………than intrinsic pathway

Answer 17

rapid

Question 18

Extrinsic pathway potentiates intrinsic pathway by

Answer 18

Trace amount of thrombin formed by extrinsic system activates
factor V & VIII which are involved in the intrinsic system.
Activated factor VII share in activation of factor IX

Question 19

•Platelet plug release chemical agents

(Platelet Release Reaction) as:

Answer 19

♠ ADP → platelets aggregation
♠ Serotonin, epinephrine & TxA2 → potent V.C.
♠ PF3 → catalyzes the clotting mechanism

Question 20

fibrin stabilizing factor

Answer 20

(factor XIII)

Question 21

platelet-derived growth factor (PDGF)……………………

Answer 21

→ stimulates wound healing

Question 22

Sources of Vitamin K in Human Body…

Answer 22

♣ Bacteria including human intestinal normal flora

♣ Diet

Question 23

•Importance of Vitamin K

Answer 23

It is necessary for liver formation of
♣ Prothrombin
♣ Factors VII, IX and X
♣ Protein C and protein

Question 24

•Absence of Vitamin K

Answer 24

→ Deficiency of factors II, VII, IX, X from blood

→ Bleeding tendency

Question 25

. What is the order of blood clotting?

Answer 25

Thromboplastin, prothrombin, thrombin, fibrinogen, fibrin

Question 26

chemical released by endothelial cells and platelets ……………… ,………. , which cause VC.

Answer 26

thromboxane A2 ,

serotonin

Question 27

Formation of temporary platelet plug(Primary hemostasis)

Answer 27

adhesion ,
activation ,
aggregation .

Question 28

binding of platelets to the collagen induces………..

Answer 28

platelet activation

Question 29

Adenosine Diphosphate ( ADP)

Answer 29

aggregated platelets

Question 30

Von Willebrand factor (VWF) secreted by ………………..and forms a ……………..

Answer 30

endothelial cells ,

bridge between BV. and platelets

Question 31

inhibit aggregation …………

Answer 31

prostacyclin (PGI2)

Question 32

The extrinsic pathway factors

Answer 32

III , VII , X

Question 33

The intrinsic pathway factors

Answer 33

XII , XI , IX , X

Question 34

VIII help in + of factor …………………….

Answer 34

IX

Question 35

NOT synthesis in liver …………., …………, …………..,

Answer 35

IV , XIII , III

Question 36

prothrombin activator ………………,…………,……………….,…………,

Answer 36

V , X , Ca++ , phospholipids

Question 37

decrease Ca++ lead to ……………

Answer 37

bleeding

Question 38

IX need…………..

Answer 38

VIII and phospholipids

Question 39

X need ……………..

Answer 39

V and phospholipids