1.1 Why does a Blood Clot form in Arteries?

Question 1

When is a Blood Clot likely to form?

Answer 1

• Blood vessel walls are damaged or blood flows very slowly, a blood clot is likely to form.

Question 2

What happens when Platelets come into contact with the damaged blood vessel?

Answer 2

• Platelets (type of blood cell without a nucleus) come into contact with the damaged blood vessel,
  
  • Platelets change from flattened discs to spheres with long projections.

Question 3

When the cell surface of the platelet changes what happens? What is formed?

Answer 3

• Cell surface changes and sticks to exposed collagen in the wall and to each other to form a platelet plug.

Question 4

What does direct contact of blood with collagen do?

Answer 4

Direct contact of blood with collagen with in the damaged artery triggers chemical changes in the blood.

Question 5

What is soluble plasma protein prothrombin converted to?

Answer 5

• Solube plasma protein prothrombin is converted to thrombin.

Question 6

What does the Thrombin enzyme catalyse the conversion of?

Answer 6

• Thrombin enzyme catalyses the conversion of another soluble plasma protein fibrinogen into long insoluble strands of the protein fibrin.

Question 7

What does Fibrin do?

Answer 7

Forma a tangled mesh that traps blood cells to form a blood clot.

Question 8

Blood Clot (3)

Answer 8

1. Platelets stick to damaged wall of blood vessel.
   - Thromboplastin is released from damaged tissue and from platelets.
   - Ca2+ and Vitamin K in plasma.
   2. Platelets stick to damaged wall and to each other forming a platelet plug.
   3. Fibrin mesh traps blood cells, forming a clot.
   Prothrombin=thrombin=soluble fibrinogen=insoluble fibrin

Question 9

Why do Blood clots only form in arteries?

Answer 9

Arteries get atherosclerosis because fast-flowing blood in arteries is under high blood pressure so there is a significant chance of damage to the walls.
Low pressure in the veins means that there is less risk of damage to the walls.