Expansion
The greatest fall occurs across the arterioles
Expansion
Approximate mean pressures:
| Site | Pressure |
|---|---|
| Aorta | 95 mmHg |
| Large arteries | 90 mmHg |
| Arterioles | 60 falling to 30 mmHg |
| Capillaries | 30 falling to 15 mmHg |
| Venules | 15 mmHg |
| Vena cava / right atrium | 0 to 5 mmHg |
The arterioles account for the largest single drop, which is why they are called the resistance vessels. Their smooth muscle is richly innervated and highly responsive, so they perform two jobs at once: setting systemic vascular resistance and therefore arterial pressure, and setting capillary hydrostatic pressure and therefore fluid exchange.
Pulsatility is also progressively damped, disappearing by the capillary level, so capillary flow is continuous. That damping is provided by the Windkessel elasticity of the great arteries.