Physiology: Special Circulation

Question 1

What is the coronary circulation?

Answer 1

Coronary blood flow
- increases during heavy exercise
- 95% of coronary venous blood returns to coronary sinus, rest drains through the anterior coronary and thebesian veins
Coronary circulation is the shortest in the human body.

Question 2

Where do the thesbian veins drain?

Answer 2

Left ventricle - slight deoxygenation of arterial blood

Question 3

What are the special tasks of the coronary circulation?

Answer 3

Maintain high basal supply of oxygen

Increase the oxygen delivery in proportion to demand (e.g. in proportion to cardiac work)

Question 4

What are the special features of cardiac muscle?

Answer 4

Size of muscle fibre diameter is small

Increased number of capillaries

Question 5

What does a high density of capillaries allow?

Answer 5

Big surface area for oxygen transfer

Short diffusion distance into cardiomyocyte

Question 6

What is important to note about the oxygen extraction?

Answer 6

Despite the high flow of blood, the myocardium has to extract 65%-75% if the oxygen to meet its demand.