Basics Coronary Blood Flow

• Coronary Blood Flow pt1:

  • All major vessels lie in the epicardium of the heart but give off smaller branches that perpendicularly penetrate into the myocardial muscle mass travelling inwards towards the endocardium
  • The coronary arteries divide into arterioles, capillaries and later re-assemble into venules and veins
  • The arterioles branch into numerous capillaries that lie adjacent to cardiac myocytes
  • A high capillary to cardiomyocyte ratio and short diffusion distances ensure efficient oxygen delivery to the myocytes and removal of metabolic waste products from the cells (e.g., CO2 and H+)
• Coronary Blood Flow pt2:

  • Note: in less healthy individuals capillarisation will be poorer, diffusion distances greater and gaseous exchange will be less efficient
  • In short: the aerobic capacity of the heart will be compromised
  • Note: Exactly the same mechanism lies behind aerobic fitness whether we are talking about heart muscle or type 1 skeletal muscle
• Coronary Blood Flow pt3:

  • After passing through the myocardium in the rich capillary networks, the now venous blood is transported via the coronary veins, (following roughly the same routes as the arteries)
  • Most of these veins join up to form an enlarged vein known as the coronary sinus
  • The coronary sinus empties venous blood directly into the right atrium