Topic 11: Cardiovascular System - Hemostasis

Question 1

What is hemostasis?

Answer 1

• process of stopping bleeding

Question 2

What 5 steps does hemostasis involve?

Answer 2

1) Vascular Spasm
2) Platelet Plug Formation
3) Clot Formation
4) Clot Retraction and Repair
5) Fibrinolysis

Question 3

What occurs in vascular spasm (2)

Answer 3

vasoconstriction of damaged arteries, arterioles
- decreases blood flow (minutes to hours)

Question 4

What occurs in platelet plug formation? (3)

Answer 4

• platelets stick to damaged blood vessel
• release chemical (factors)
• neighbouring healthy endothelial cells release a chemical preventing spread of plug

Question 5

When chemical factors are released in platelet plug formation, what do they do? (3)

Answer 5

1) cause more platelets to stick
2) Promote clotting
3) begin healing

Question 6

What does plug formation require, and what is it inhibited by?

Answer 6

• needs a prostaglandin
• inhibited by aspirin (ASA)

Question 7

What are the 3 stages of clot formation?

Answer 7

• production of prothrombin activator
• prothrombin converted to thrombin
• fibrinogen converted to fibrin

Question 8

In clot formation, what occurs in production of prothrombin activator stage? (3)

Answer 8

Extrinsic pathway - uses factors released by damaged tissues
Intrinsic pathway - uses factors contained in blood
- both occur together and require calcium, tissue, platelet and/or plasma factors

Question 9

Prothrombin converted to thrombin diagram

Answer 9

uses a prothrombin activator

Question 10

Fibrinogen converted to fibrin diagram

Answer 10

uses thrombin and calcium

Question 11

What type of feedback is thrombin in clot formation?

Answer 11

positive because it increases its own formation

Question 12

How many clotting factors are involved in clot formation? (3)

Answer 12

2 dozen
- from diet, liver (plasma proteins), damaged tissues, and platelets
- ex. vitamin K required for the synthesis of 4 factors

Question 13

What occurs in clot retraction and repair? (2)

Answer 13

retraction - blood vessel edges pulled together
repair - fibroclasts form new CT and new endothelial cells repair lining

Question 14

What occurs in fibrinolysis? (3)

Answer 14

• clot dissolution
  fibrin digesting enzyme = plasmin (see diagram)
• phagocytes then remove clots in clumps

Question 15

What is a thrombus?

Answer 15

• a stationary clot in an undamaged vessel

Question 16

What is an embolus?

Answer 16

• free floating clot

Question 17

What is hemophilia? (2)

Answer 17

• clotting abnormal/absent
• about 83% is type A, meaning they lack clotting factor VIII