Cardiovascular System

As volume flow rate is proportional to radius to the fourth power, if radius decreases by half, volume flow rate decreases by ½ × ½ × ½ × ½ = 1/16.

This is one of the factors in Poiseuille’s law upon which volume flow rate depends: V ∝ R⁴

Heart rate contributes to cardiac output but not peripheral resistance.

Veins have valves but not pulsatile flow or a thick layer of smooth muscle.

The pulmonary circulation refers to the flow of blood from the heart (via the pulmonary trunk) through the lungs and back to the heart.

As particles of a gas are moving at high speed (hundreds of metres per second) and in random directions, every direction will have some particles moving in that direction. Hence a region with fewer particles (i.e. at a lower pressure) will have more particles moving into it than are moving away from it. This will tend to eliminate volumes with different pressures.

2 mm is half of 4 mm and according to Poiseuille’s law: V ∝ (1/2)⁴ = 1/16

Boyle’s law relates gas pressure and gas volume.

The mitral valve is the left atrioventricular valve.

Both ventricles pump the same volume of blood at all times. If, for example, the left ventricle pumped less blood than the right, blood would accumulate in the lungs. This would happen with congestive heart failure.