W143 Haemostasis

Question 1

what are the three stages of haemostasis?

Answer 1

1. vascular stage (vasoconstriction)
2. platelet phase (aggregation and plug)
3. Coagulation phase

Question 2

what is the first thing that occurs after a break in the blood vessel wall?

Answer 2

VASOCONSTRICTION!!!

Question 3

What is quickly released after damage to endothelial walls?

Answer 3

ADP
Tissue factor (FIII)
prostacyclin
endothelins

Question 4

what factor number is tissue factor?

Answer 4

III

Question 5

what does tissue factor (aka FIII) do?

Answer 5

Activation of thrombin (from prothrombin)

aka

Prothrombin —–[FIII]——> Thrombin

Question 6

what do endothelins do?

Answer 6

primary hormones in vascular phase: smooth muscle contraction

Question 7

how many platelets are stored in the spleen at any one time?

Answer 7

a third (33%)

Question 8

What is low platelet count called?

Answer 8

thrombocytopaenia

Question 9

what is high platelet count called?

Answer 9

thrombocytosis - infection, inflammation, cancer

Question 10

what controls platelet formation?

Answer 10

thrombopoiesis (TPO) mainly produced in LIVER

Question 11

when does the platelet phase begin?

Answer 11

as soon as platelets begin to attach themselves to damaged areas of endothelium- normally collagen

this happens within 15 seconds of injury (hence PT time)

Question 12

what two types of granule are released by activated platelets?

Answer 12

alpha- fibrinogen and PDGF

dense- non protein things eg. thromboxane, serotonin, adrenaline, histamine, calcium, ATP, ADP

Question 13

what genetic disorder is caused by a lack of platelet alpha granules? and how is it inherited?

Answer 13

grey platelet syndrome

autosomal dominant

rare

causes reduced clotting

Question 14

what reduces platelet plug formation?

Answer 14

prostacyclin released by endothelium

white blood cell proteins

Question 15

what is the activated form of fibrinogen called?

Answer 15

fibrin duhhh

Question 16

what is the single most important protein involved in clotting?

Answer 16

fibrinnnnnnnnn

Question 17

what does fibrin do?

Answer 17

forms fibrin threads to stabilise platelet plug: forms a blood clot!

Question 18

how long after initial injury does the coagulation phase start?

Answer 18

about 30 seconds

Question 19

Before the common pathway is joined, what does the intrinsic cascade ultimately form?

Answer 19

Factor X activating factor ‘tenase’

XIIa –> XIa –> +Ca –> IXa –> +PF3 –> VIIIa –> +IXa –> tenase

Question 20

what factors are in intrinsic pathway?

Answer 20

XII, XI, IX, VIII (+PF3)

Question 21

describe the extrinsic pathway

Answer 21

Begins in vessel wall.

Damaged cells release tissue factor (FIII).

Combines with Ca to activate FVII.

The VIIa-III complex is quickly inactivated by antithrombin III.

Question 22

what factors are involved in extrinsic pathway?

Answer 22

III, VII