Vascular Disturbances 3

Question 0

What triggers thrombus formation?

Answer 0

1. Damage to endothelial cells
2. Sluggish/ turbulent blood flow
3. Hypercoagulable blood
   10

Question 1

What is a thrombis?

Answer 1

A solid aggregate of platelets, proteins and blood cells formed in a blood vessel of a living animal.
Slide 7

Question 2

Regulation of haemostasis

3 main system are?

Answer 2

1. Anti thrombin-3:
   - inhibits thrombin and factors 9a and 10a
2. Protein C and S
   Protein C: major regulatory pathway, vitamin K dependant, degradation of factors 5 and 8, activated by thrombin binding to endothelial cell receptors thrombomodulin, neutralises inhibitor of tissue type plasminogen activator thus promoting conversion of plasminogen to plasmin and fibrinolysis.

Protein C with the help of thrombomodulin which is found in endothelial cells becomes activated protein C. Protein C and S will cleave and inactivate Factor 5a and 8a therefore leading to anti-coagulation.

3. Fibrinolytic System
   Fibrinolysis: plasmin will cause fibrinolysis, plasmin activation is the result of; factor 12, plasminogen activators, bacterial streptokinase and bacterial walls and low O2 tension.

Fibrinolytic system: 
1. Plasminogen ➡ plasmin (active) 
2. Enzyme plasmin causes 
   Fibrin➡ fibrin degradation products 
Fibrin = fibrinogen, coagulation factors 5 and 8, and prothrombin 

Tissue plasmin activator is released from endothelial cells at a steady date and limits spread of clots away from we’re it is needed.

Slide 10

Question 3

What is an embolism?

Answer 3

Plug of material within the circulation, which may eventually become lodged within a vessel too narrow to allow it to flow through
.
Sources: thrombi, bacteria, parasites, fat, amniotic fluid, bone marrow, air, tumour cells etc

Question 4

What are the consequences of embolism?

Answer 4

Ischeamia
Spread of infection
Systemic inflammation
No consequences (collateral blood supply, bland embolus)

Question 5

Understand and be able to explain each section of the coagulation cascade on slide 11 and 13

Answer 5

Important

Question 12

What are the consequence of a thrombosis: once formed, a thrombus may:

Answer 12

1. Cause immediate death, depending on location
2. Be be lysed by fibrinolytic system; plasmin causes the lysis (breaking down of cell) of fibrin and also initiates inflammatory processes by activating factor 12 and initiating the complement cascade by cleaving C3
3. Undergo organisation
4. Produce emboli

Question 13

The major predisposing factors for thrombosis are also known as?

Answer 13

VIRCHOWS triad

1. Damage to the endothelial surface
2. Sluggish or abnormally turbulent blood flow
3. Hypercoagulability

Question 14

Difference between a thrombus and a post mortem (after death) clot

Answer 14

Thrombus:

• dry, granular and rough, white and buff, stratified, adherent to wall
• vascular endothelium, rough or damaged under the mass
• composed primarily of fused platelets
• formed in a flowing stream during life
• may be partially organised
• vary in shape

Clot:

• moist
• smooth and shiny
• red or yellow
• uniform
• unattached
• vascular endothelium intact and smooth
• composed mainly of fibrin with all blood elements trapped
• composed mainly of fibrin with all blood elements trapped
• formed in stagnant column of blood in dead or dying
• never organised
• mould vessel like jelly

Question 15

What is disseminated intravascular coagulation (DIC)

Answer 15

• serious complication of severe systemic disease
• widespread activation of coagulation cascade with the formation of fibrin
• ultimately depletes circulation of platelets and coagulation factors
• also concomitant activation of fibrinolytic system
• consequently there is wide spread bleeding