hemostasis

Question 1

What is hemostasis?

Answer 1

stoppage of bleeding in response to blood vessel damage

Question 2

what is hemostasis triggered by

Answer 2

chemicals released/ activated by damaged cells & platelets

Question 3

what is the purpose of hemostasis

Answer 3

to prevent blood loss

build a framework for tissue repair

Question 4

What are the 3 major phases of hemostasis

Answer 4

1) Vascular phase
2) platelet phase
3) coagulation phase

Question 5

What are the 4 major events in hemostasis

Answer 5

1) Vascular spasm
2) platelet plug
3) Activation of platelets
4) Coagulation

Question 6

What is the major event that happens in the vascular phase?

Answer 6

• Vascular spasm

Question 7

What is a vascular spasm

Answer 7

vessel spasms in damaged blood vessel.

the smooth muscle contracts to reduce blood flow to injured site

Question 8

what do the endothelial cells (lining of the vessel) do during the vascular phase?

Answer 8

release endothelins

Question 9

what are endothelins?

Answer 9

Peptide hormones that:

• Stimulate contraction of smooth muscle
• make endothelium sticky
• stimulate division/repair

Question 10

What are the 2 major events of the platelet phase?

Answer 10

1) Formation of platelet plug

2) activation of platelets

Question 11

What do the platelets begin by doing in the platelet phase?

Answer 11

they adhere to the collagen fibres that are exposed when the endothelium is damaged

Question 12

what is the von willebrand factor purpose?

Answer 12

it stabilized the bound platelets when they begin to adhere to the collagen

Question 13

what happens when the platelets begin to aggregate

Answer 13

as the become sticky, they become activated by aggregating to each other and this forms a PLATELET PLUG !!

Question 14

What do the activated platelets release?

Answer 14

granules of:

• Sereotinin
• thromboxane, A2+ ADP
• PDGF
• Ca2+

Question 15

What does serotonin do?

Answer 15

Stimulates more vascular spasm & platelet aggregation

Question 16

what does the thromboxane A2+ ADP do?

Answer 16

stimulates platelet aggregation

Question 17

What does the platelet derived growth factor do?

Answer 17

promotes vessel repair

Question 18

what does the ca2+ do?

Answer 18

it promotes coagulation

Question 19

is formation of platelet plug positive or negative feedback mechanism ?

Answer 19

Positive! +++

Question 20

what is coagulation?

Answer 20

Blood clotting (liquid to gel) 
the result of this will be a clot

Question 21

what is clot?

Answer 21

a tangle of fibrin & cells

Question 22

what are clotting factors?

Answer 22

proteins in the blood (many are enzymes)
the circulate as inactivated procoagulants
they must be activated for coagulation to occur (by an enzyme)
they are numbered I - XIII (in the order they were discovered)

Question 23

Where are clotting factors made?

Answer 23

the liver

Question 24

what do clotting factors require to be made?

Answer 24

VITAMIN K

Question 25

What are the 2 clotting pathways

Answer 25

1) intrinsic 2) Extrinsic * Both go into common path tho

Question 26

where is the intrinsic pathway initiated

Answer 26

within the blood

Question 27

what triggers the intrinsic pathway?

Answer 27

when clotting factor XII and platelets are activated by COLLAGEN

Question 28

what does intrinsic pathway require?

Answer 28

Platelet phospholipid (PF3) expressed when platelets are exposed to collagen

Question 29

where is collagen?

Answer 29

In the C.T and walls of the torn vessel

Question 30

Why does the intrinsic pathway occur in test tube?

Answer 30

they are a negatively charged surface... | It has the same effect as collagen

Question 31

Is the intrinsic pathway slow or fast?

Answer 31

SLOW :-(

Question 32

what initiates the extrinsic pathway?

Answer 32

chemical external to the blood

Question 33

what triggers the extrinsic pathway?

Answer 33

chemical released by damaged cells | TISSUE FACTOR

Question 34

what does tissue factor do?

Answer 34

activates platelets

Question 35

What is tissue factor also known as?

Answer 35

thromboplastin

Question 36

is the extrinsic pathway slow or fast?

Answer 36

Faster! under 2 mins

Question 37

What do both pathways do?

Answer 37

activate factor X

Question 38

what does clotting factor X do

Answer 38

Initiates the common pathway.. which will result in a network of fibrin

Question 39

do both extrinsic and intrinsic pathways usually occur simultaneously or just usually one or the other?

Answer 39

simultaneously activated in most cases

Question 40

What is hemophilia

Answer 40

a genetic defect in 1+ genes that code for clotting factors affected individuals have blood that won't clot normally ( its usually VIII factor...)

Question 41

What is a a thrombus

Answer 41

clot that forms in blood vessels of the heart and partially or completely obstructs flow

Question 42

what is an embolus

Answer 42

any detached, intravascular mass that is carried by circulation, which is capable of clogging blood vessel

Question 43

what is meant by clot retraction

Answer 43

shrinking of a clot

Question 44

what is meant by fibrinolysis

Answer 44

breaking down of fibrin

Question 45

What ion is needed for clot formation

Answer 45

calciummm

Question 46

[ activated factor X] & [Ca2+] & [activated factor V] =

Answer 46

prothrombinase - a complex of Xa & Va | it is now a FUNCTIONAL enzyme

Question 47

what does prothrombinase activate?

Answer 47

Prothrombin (II)

Question 48

What is the activated form of prothrombin called?

Answer 48

thrombin (IIa)

Question 49

What does thrombin activate?

Answer 49

fibrinogen (I)

Question 50

what is the activated form of fibrinogen?

Answer 50

fibrin (Ia)

Question 51

what happens when fibrin is activated?

Answer 51

insoluble cross-linked fibrin mesh and trapped cells AKA A CLOT !!

Question 52

what do the platelets do first to break down a clot?

Answer 52

release PDGF: promotes healing of the vessel wall

Question 53

what do the endothelial cells do to break down the clot?

Answer 53

they release TPA (tissue plasminogen activator)

Question 54

What does TPA do?

Answer 54

it activates plasminogen (plasma protein that is trapped in the clot)

Question 55

what is the activated form of plasminogen

Answer 55

plasmin

Question 56

what does plasmin do?

Answer 56

it is a fibrin digesting enzyme | it is the cause of fibrinolysis

Question 57

what is fibrinolysis

Answer 57

retracted clot is dissolved as fibrin is digested by plasmin over several days

Question 58

what else is happening within the clot during breakdown?

Answer 58

Clot retraction

Question 59

what is clot retraction?

Answer 59

The platelets contract and pull torn edges of the damaged vessel closer together to make repair easier

Question 60

how are the platelets able to contract??

Answer 60

because they contain actin & myosin like a muscle

Question 61

What happens to the serum during clot breakdown

Answer 61

it is squeezed out of the clot

Question 62

what is serum?

Answer 62

plasma without any clotting proteins in it