Hemostasis. Characteristics of platelets. Formation of platelet plug.

Question 1

hemostasis - definition

Answer 1

• blood clotting
• preventing excessive blood loss
• maintaining sufficient bloodflow around body

Question 2

hemostasis - step 1

Answer 2

vasospam

• right after cut the blood vessels constrict their flow to prevent blood from flowing to broken area causing blood loss
• smooth muscle contraction
• cell signalling molecule of endothelial to release NO + PROSTACYCLIN 2 = anticoaggulants

Question 3

hemostasis - step 2

Answer 3

platelet adhesion

• exposed platelets are adhered together
• von willebrand factor
• subendothelial collagen

Question 4

hemostasis - step 3

Answer 4

platelet activation

platelets release chemical granules
- serotonin
- ADP
- thromboxane A2

to form positive feedback mechanism to amplify response

Question 5

hemostasis - step 4

Answer 5

platelet aggregation

fibrinogen + GPIIa + GPII receptors = formation of primary platelet plug

Question 6

hemostasis - step 5

Answer 6

extrinsic pathway

caused by subendothelial cells + exposed tissue factor

factor 3 -> factor 7 -> factor 7a -> factor 10 -> factor 10a (enters common pathway)

Question 7

hemostasis - step 6

Answer 7

intrinsic pathway

cause = bloods platelet gets into contact with collagen fibres + damaged blood vessel =

factor 12 -> factor 12a -> factor 11

factor 11a -> factor 9a + factor 13a = tenase complex formation on surface of activated platelets

factor 10 -> factor 10a = common pathway

Question 8

hemostasis - step 7

Answer 8

common pathway

extrinsic (initial) + intrinsic (amplifier) activated by factor X

1 - factor 10a + factor 5a converts prothrombin into thrombin

2 - fibronogen converted to fibrin via thrombin

3 - fibrin formed meshwork clot

Question 9

hemostasis - final stage

Answer 9

clot retraction = removal of fibrin clot
- dissolved by fibrinolysis + plasminogen activator

Question 10

platelets - 1

Answer 10

size

diameter = 3mm

Question 11

platelets - 2

Answer 11

shape

inactive = flat
active = spherical

Question 12

platelets - 3

Answer 12

origin - TPO

Question 13

platelets - 4

Answer 13

anucleated
rich in cytoplasm

Question 14

platelets - 5

Answer 14

granules
- alpha granules -> contains fibrinogen + VWF for blood clotting
- dense granules -> storage of ADP/ serotonin for platelet activation
- lysosomes = hydrolytic digestive enzymes to break down cellular debris