Haemostasis

Question 1

Why clot

Answer 1

to keep blood in and pathogens out

Question 2

what is haemeostasis

Answer 2

physiological process that stops bleeding at the site of an injury whilst maintaining normal blood flow elsewhere

Question 3

primary

Answer 3

1. adhere
2. activate
3. aggregate

Question 4

secondary

Answer 4

thrombin (Protease)cleaves circulating soluble fibrinogen into insoluble fibrin mesh

Question 5

1. adherence- endothelium releases what

Answer 5

von willebrand factor

Question 6

1.adherence- where is von willebrand factor stored

Answer 6

Weibel-Palade bodies in endothelial cells

Question 7

1.adherence - what does von willebrand bind to

Answer 7

exposed collagen

Question 8

1.adherence- what do platelets express receptors for

Answer 8

collagen and functional fibrinogen receptors

Question 9

1.adherence- what happens to platelets when bound

Answer 9

activated

Question 10

2. activation- what do platelets bind to

Answer 10

fibrinogen

Question 11

2. activation- what do platelets release after binding to fibrinogen

Answer 11

multiple pro activation signalling molecules e.g adenosine diphosphate (ADP) + thromboxane A2 (TXA2)

Question 12

3. Aggregation

Answer 12

linking of platelets- activated by other platelets, dont need to see wound

Question 13

Secondary- what is the sub-endothelial trigger for coagulation cascade

Answer 13

tissue factor

Question 14

Amplification- each activated factor activates more of the next (5)

Answer 14

1. activated platelet(signalling molecules +fibrinogen)
2. initial trickle of thrombin
3. Tissue factor(TF)- expressed by sub endothelial cells- activates coagulation cascade to initiate minor burst of heamostasis
4. Factor 7a binds to TF which leads to conversion of prothrombin- thrombin
5. thrombin activates receptors on platelets + endothelium -amplifying + initiating release of stored von willebrand from cells

Question 15

Secondary(amplification)- what activates coagulation cascade

Answer 15

tissue factor

Question 16

Secondary(amplification)- what binds to TF

Answer 16

Factor 7a

Question 17

Secondary(amplification)- binding of factor 7a to TF leads to what

Answer 17

conversion of prothrombin to thrombin

Question 18

Secondary(amplification)- what does thrombin activate

Answer 18

receptors on platelets and on endothelium- release of more von willebrand

Question 19

Secondary- what two cofactors does thrombin activate

Answer 19

factor 8a and 5a

Question 20

what are the two calcium ion dependant complexes on the surface of platelets called

Answer 20

1. prothrombinase complex (factor 5a)

2. tenase complex (factor 4a)

Question 21

what does the prothrombinase complex (factor5a) accelerate the production of

Answer 21

factor 5a

Question 22

what does the tenase complex (factor 4a) accelerate the production of

Answer 22

thrombin

Question 23

what is heamophilia

Answer 23

failing to clot

Question 24

thrombosis

Answer 24

clotting in the wrong place e.g arterial(stroke)

venous(DVT)

Question 25

disseminated intravascular coagulation(DIC)

Answer 25

whole body clots- sepsis

depletion of clotting factors and platelets lead to bleeding

Question 26

why is coagulation activated during sepsis

Answer 26

can be beneficial during infections since proteins are necessary for eradication of invading pathogens

Question 27

what is the containment hypothesis

Answer 27

coagulation activation contributes to pathogen clearance by forming a physical barrier facilitating pathogen clearance by immune cells