Platelet Plug & Coagulation Cascade

Question 1

When a blood vessel is damaged, what is its first response?

Answer 1

To vasoconstrict (due to neural control)

Question 2

What initiates a platelet plug and coagulation cascade?

Answer 2

Endothelial damage

Question 3

What is released by healthy endothelium & what does it do?

Answer 3

Nitric oxide (NO)  and prostacyclin
Vasodilates (keeps blood vessels open)

Question 4

When a blood vessel/endothelium is damaged what is released and what does it do?

Answer 4

Endothelin-1 is released (by endothelial cells) and is used to vasoconstrict

Question 5

What does vasoconstriction do?

Answer 5

Temporarity slows the flow of blood in the affected area

Question 6

What also happens with the blood vessel?

Answer 6

This construction presses opposed endothelial surfaces of the vessel together and this contact induces a stickiness capable of keeping them glued together

Question 7

What only occurs in the smaller vessels of the microcirculation?

Answer 7

Permanent closure of the vessel by constriction and contact stickiness

Question 8

What are the two processes that stop bleeding?

Answer 8

Formation of a platelet plug and blood coagulation

Question 9

What is found below endothelium and what happens to it when a vessel is injured?

Answer 9

There is collagen fibres

Injured vessels means endothelium is disrupted and exposes collagen fibres

Question 10

What binds to exposed collagen?

Answer 10

Von willebrand factor (VWF) (factor 8) binds to exposed collagen at injured endothelium using glycoprotein 1B (GP1B) receptor

Question 11

What happens after VWF binds to collagen?

Answer 11

Platelet adhesion - platelets bind to VWF on collagen via a GPIIa/IIIb receptor

Question 12

What happens after platelets bind to VWF?

Answer 12

Binding triggers activation

Platelets are activated

Question 13

What happens when platelets are activated?

Answer 13

Inactive: smooth & discoid
Active: spiculated (spiky) & pseudopoid
Exocytosis (release) of alpha/electron granules, amplified positive feedback, platelet aggregation

Forms a primary platelet plug

Question 14

What happens after the platelet plug?

Answer 14

A coagulation cascade

Question 15

What does the coagulation cascade form?

Answer 15

forms a mesh of fibrin over the primary platelet plug to make it more stable/add reinforcement

Forms secondary platelet plug

Question 16

What are the 3 Pathways of the Coagulation cascade?

Answer 16

Intrinsic
Extrinsic
common

Question 17

What are the 3 Pathways of the Coagulation cascade?

Answer 17

Intrinsic
Extrinsic
common

Question 18

Describe the intrinsic pathway and its path

Answer 18

Uncommon
trauma inside blood vessels (internal damage)

12, 11, 9, 8, 10

Question 19

Describe the extrinsic pathway and its path

Answer 19

Common
Extravascular trauma
Tissue factor 3 from damaged tissues activates 7

3, 7, 10

Question 20

Describe the common pathway and its path

Answer 20

10 at the centre
activates 2 (with help of 5)
Factor 2: prothrombin ---> thrombin
2 activates 1
Factor 1: fibrinogen ---> fibrin

10, 5, 2, 1

Question 21

What is the Fibrinolytic system?

Answer 21

A fibrin clot is not designed to last forever, it is a temporary fix until permanent repair of vessel occurs

Question 22

What happens when vessel is fixed?

Answer 22

The secondary platelet plug is hydrolysed

Question 23

What happens in the hydrolysis of the 2* platelet plug?

Answer 23

Tissue plasminogen activators convert plasminogen —> plasmin (fibrin eater)

Plasmin eats fibrin; fibrin —> fibrinogen (inactive)

Question 24

Where are all clotting factors except one produced and which one?

Answer 24

All clotting factors except Von Willebrand Factor are produced in the liver

Question 25

The liver is the site of production for?

Answer 25

Many of the plasma clotting factors

Question 26

What does the liver produce and what is it essential for?

Answer 26

Bile salts

absorption of the lipid soluble substance, vitamin K

Question 27

Why does the liver require vitamin K?

Answer 27

To produce prothrombin & several other clotting factors

Question 28

Which factors are vitamin K dependent?

Answer 28

10, 9, 7, 2

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