Platelets and hemostasis

Question 1

Platelets aka

Answer 1

thrombocytes

Question 2

platelets dervied from

Answer 2

cytoplasm fragmentation of megakaryocytic (goat multinucleate cells)
promote blood clotting and help repair gaps in walls of blood vessels, prevent blood loss

Question 3

Platelets

Answer 3

small, disc shaped, non-nucleated cell fragments

Question 4

Hyalomere

Answer 4

peripheral light blue stained zone

Question 5

Granulomere

Answer 5

darker zone with purple granules

Question 6

Platelet structure

Answer 6

alpha granules: largest. Vessel repair, blood coagulation, platelet aggregation
Delta granules: facilitate platelet adhesion, vasoconstriction. Contain ATP, ADP, histamine, serotonin
Lamda granules: clot resorption

Question 7

Stages of hemostasis **need to know

Answer 7

1) Vascular wall injury and exposure of sub-endothelial collagen
2) Vasconstriction
3) Formation of platelet plug
4) Coagulation cascade
5) Formation of fibrin clot (plug)
6) Healing and fibrinolysis

Question 8

Platelet functions in hemostasis

***need to know

Answer 8

1) Adhesion to the injured surface
2) Shape change
3) Release of granule contents
4) Aggregation

Question 9

Mechanism of Hemostasis

She will test

Answer 9

1) Blood vessel wall injured, collagen fibers exposed at damaged site
2) release of endothelia (vasoconstrictor) and von Willebrand factor (vWF) which binds exposed collagen fibers
3) Platelets adhere to exposed collagen by binding to vWF and they get activated (platelet activation)
4) Conversion of fibrinogen to fibrin
5) clot shrinks
6) Vessel wall repaired

Question 10

Coagulation pathway

Answer 10

Calcium-dependent pathway

Vitamin K dependent factors II, VII, IX, X

Question 11

Instrinsic pathways

Answer 11

Begins with activation of F XII -> XI-> IX (calcium required) -> IX a (activated) -> F IX + VIII = F X

12 -> 11-> 9 + calcium -> 9 +8 -> 10
Calcium and phospholipid are required

Question 12

Extrincitic pathway

Answer 12

1st to kick in
Depends on release of tissue factor (TF) thromboplastin (F III)

TF binds to F VII

F III aka thromboplastin complex converts F X -> F Xa
calcium converted

VII + TF = X –> Xa

Question 13

Prothrombrin (F II) —> Thrombin (II a)

Answer 13

In presence of calcium, phospholipid and F V is converted

Question 14

Thrombin converts

Answer 14

Factor XIII —> XIII active (clot formation)

Question 15

Essential Thrombocythemia

Answer 15

increased platelet count

Genetic JAK2 mutation

Question 16

Thrombus

Answer 16

clot that develops & persists in an unbroken blood vessel

Question 17

Embolus

Answer 17

thrombus that becomes dislodged or fragmented freely circulating in the blood stream; thromboembolism

Question 18

Bleeding disorders

Answer 18

decreased # of platelets

Vitamin K required by the liver as cofactors VII, IX, X and prothrombin

Question 19

Hemophilia

Answer 19

sex-linked inherited genetic disorder

spontaneous hemorrhages

Question 20

Hemophilia A

Answer 20

defect in factor VIII

Only males effected. Females carry

Question 21

Hemophilia B

Answer 21

defect in factor IX (christmas factor)

Question 22

Von Willebrand’s disease (vWD)

Answer 22

defective platelet plug formation
autosomal dominant trait
most common blood clotting disorder

Question 23

Thrombocytopenis

Answer 23

decreased platelet count
Caused by decreased platelet production, increased platelets destruction

Purpura and petechiae- patches on skin

Question 24

Immune or idiopathic thrombocytopenia purport (ITP)

Answer 24

accelerated antibody-mediated platelet consumption- failure of blood to clot
Spleen makes antibodies against antigens (GPIb)
Platelets are destroyed in spleen by macrophages