19.5 hemostasis

Question 1

define hemostasis

Answer 1

arresting or stopping of bleeding

Question 2

in hemostasis a series of events helps prevent

Answer 2

excessive blood loss

Question 3

what is the immediate response in a damaged blood vessel?

Answer 3

vascular spasm

Question 4

describe vascular spasm

Answer 4

the immediate but temporary response to vascular damage, due to smooth muscle cntx in the wall

Question 5

what type of stimulus will create a vascular spasm

Answer 5

upon tissue damage:
reflex
thromboxane released by platelets
endothelin released by endothelial cells

Question 6

what are thromboxanes?

Answer 6

prostaglandin derived chemical released by platelets that trigger vascular spasm

Question 7

what is endothelin?

Answer 7

a chemical released by endothelial cells that triggers vascular spasm

Question 8

what is a platelet plug?

Answer 8

an accumulation of platelets that seals up small holes in vessels

Question 9

what are the 3 steps of platelet plug formation

Answer 9

platelet adhesion
platelet release rxn
platelet aggregation

Question 10

how does platelet adhesion occur in a platelet plug?

Answer 10

von Willebrand factor (a protein) is produced and secreted by the damaged endothelial cells and connects the exposed collagen to the platelets

Question 11

what is vWF (von Willebrand factor)?

Answer 11

a protein secreted by the endothelial cells that connects the exposed collagen to the platelets

Question 12

describe the positive feedback mechanism of platelet release rxn

Answer 12

adhered platelets release ADP, thromboxanes and other chemicals that activate more platelets to join the plug, which in turn release the same chemicals to recruit even more platelets

Question 13

in which step of platelet plug formation is vWF released by endothelial cells?

Answer 13

step 1, platelet adhesion

Question 14

in which step of platelet plug formation do platelets release ADP, thromboxanes and other chemicals?

Answer 14

step 2, platelet release rxn

Question 15

describe platelet aggregation in platelet plug formation

Answer 15

activated platelets express surface receptors to which fibrinogen can bind
fibrinogen binds to these surface receptors and forms a bridge between other activated platelets and a platelet plug is formed

Question 16

what chemicals do platelets release once a plug is formed?

Answer 16

phospholipids (platelet factor III)
coagulation factor V
both important in clot formation

Question 17

what factors in coagulation are already in the blood stream?

Answer 17

prothrombin

fibrinogen

Question 18

what enzyme is used to change prothrombin to thrombin?

Answer 18

prothrobinase

Question 19

what does thrombin do?

Answer 19

changes fibrinogen to fibrin

Question 20

what is fibrinogen?

Answer 20

a soluble plasma protein

Question 21

what does fibrin do?

Answer 21

forms the fibrous network of a clot

Question 22

what are the coagulation factors?

Answer 22

proteins found in plasma that circulate in their inactive state until the tissues are injured

Question 23

what produces changes that begin activation of the coagulation factors?

Answer 23

damaged tissues and platelets

Question 24

what are the 2 pathways to clot formation?

Answer 24

extrinsic and intrinsic

Question 25

what is a blood clot?

Answer 25

network of threadlike fibrin fibers, trapped blood cells, platelets and fluid

Question 26

define anticoagulants

Answer 26

they prevent coagulation factors from initiating clot formation or inhibit the processes that contribute to clote formation

Question 27

when does coagulation occur?

Answer 27

when coagulation factor concentrations exceed a certain threshold at the site of injury

Question 28

what are 3 anticoagulants?

Answer 28

antithrombin heparin prostacyclin

Question 29

what does antithrombin do and where is it produced?

Answer 29

produced by liver | slowly inactivates thrombin

Question 30

what does heparin do and where is it produced?

Answer 30

produced by basophils and endothelial cells | increases effectiveness of antithrombin

Question 31

what does prostacyclin do and where is it produced?

Answer 31

prostaglandin derivative from endothelial cells causes vasodilation inhibits release of coagulating factors from platelets?

Question 32

what inhibits release of coagulating factors from platelets?

Answer 32

prostacyclin

Question 33

what inactivates thrombin?

Answer 33

antithrombin

Question 34

what increases the effectiveness of antithrombin?

Answer 34

heparin

Question 35

what is clot retraction?

Answer 35

the condensing of the blood clot to become a denser, compact structure

Question 36

how does clot retration work?

Answer 36

platelets contain actin and myosin and attach to fibrin through processes actin and myosin pull on the fibrinogen leading to clot retraction

Question 37

how is a clot dissolved?

Answer 37

plasmin (an enzyme that hydrolyzes fibrin)