Lecture 10 Unit 2

Question 1

what are platelets?

Answer 1

cell fragments that circulate for 5-9 days then die

Question 2

what’s another word for platelets?

Answer 2

thrombocytes

Question 3

2/3 of mature platelets circulate, where are the other 1/3?

Answer 3

in the spleen

Question 4

what does thrombosis refer to?

Answer 4

clot formation

Question 5

what is a clot called?

Answer 5

thrombus

Question 6

what is an embolus

Answer 6

a circulating clot

Question 7

what is a hemorrhage?

Answer 7

a severe uncontrolled bleeding

Question 8

how does thrombocytopoiesis happen?

Answer 8

myeloid stem cells produce megakaryocytes

Question 9

what does thrombopoietin do?

Answer 9

causes fragments to slough off the megakaryocyte

Question 10

what is hemostasis?

Answer 10

a series of reactions designed for stoppage of bleeding

Question 11

what happens during hemostasis?

Answer 11

1. vascular spasm
2. platelet plug formatin
3. coagulation

Question 12

what is a vascular spasm?

Answer 12

immediate vasoconstriction in response to injury

Question 13

what is coagulation

Answer 13

blood clotting

Question 14

where do vascular spams only occur?

Answer 14

in vessels with smooth muscle in wall

Question 15

what do vascular spasms react to?

Answer 15

injury

Question 16

where are vascular spasms effective?

Answer 16

only in small vessels

Question 17

what do platelets not normally stick to?

Answer 17

each other or the endothelial lining of blood vessels

Question 18

what do platelets do upon damage to a blood vessel?

Answer 18

1. stick to exposed collagen fibers and are activated allowing them to stick to one another
2. liberate thromboxane A2, serotonin and ADP which attract and activate still more platelets
3. release ADP which makes platelets sticky while thromboxane A2 and serotonin cause cell contraction

Question 19

what participates in coagulation?

Answer 19

about 30 substances and 13 clotting factors from the liver

Question 20

what actually happens in coagulation?

Answer 20

blood is transformed from a liquid to a gel

Question 21

in coagulation are the intrinsic pathways or the extrinsic pathways faster/

Answer 21

extrinsic pathways are faster

Question 22

what are the three steps in the common pathway which must be completed in order for effective clotting to occur?

Answer 22

1. once prothrombinase is activated it converts prothrombin into thrombin
2. thrombin has two main functions (-converts fibrinogen (soluble) to fibrin (insoluble) - activated factor XIII which stabilizes the fibrin network)
3. prothrombin, fibrinogen, and factors V, VII, IX, and X are synthesized in the liver

Question 23

what is vitamin K needed for?

Answer 23

synthesis of factors II, VII, IX, and X

Question 24

what can vitamin K deficiency lead to?

Answer 24

failure of blood clotting

Question 25

what happens in hemophiliacs?

Answer 25

they lack factor VIII, since factor IX requires factor VIII to work, no prothrombinase can be formed without factor VIII

Question 26

what happens in fibrinolysis?

Answer 26

clots must be dissolved so that they do not enter the circulation as an embolus

Question 27

what reacts to form plasmin?

Answer 27

tissue plasminogen activator, thrombin, and plasminogen

Question 28

what does plasmin do?

Answer 28

it digests the fibrin strands and breaks the clot