Features of pulmonary circulation
It is a low pressure system
Because it only needs to pump blood to the top of the lungs.
If it is high
pressure, then following Starling
forces, the fluid would flood the lungs.
Advantages of Pulmonary Circulation being a Low Resistance
system
- Accommodates more blood as a person shifts from the standing to the lying position.
- High compliance allows the vessel to dilate in response to modest increase in Pulmonary arterial pressure.
- Pulse pressure in the pulmonary circulation is rather low
Right Ventricle:
Systolic= 25 mmHg
Diastolic= 0-1 mmHg,
Pulmonary artery:
Systolic= 25 mmHg
Diastolic= 8 mmHg
Mean Pulmonary arterial pressure= 15 mmHg.
Pulmonary Vein:
Averages about 5 mmHg
Pulmonary capillaries:
7 mm Hg
Left atrium:
Averages 2 mmHg
It is a low resistance system
- Only 1/10th of the resistance of the systemic circulation
- Arterioles have less smooth muscle, veins are wider & shorter& pulmonary vessel walls are thinner.
- Accommodates 5 L of blood (same as the systemic circulation)
- Accommodates shifts of blood more quickly e.g. when a person shifts from a standing to a lying position
Because it needs to send blood to the brain even when
standing & to the tip of en elevated fingertip.
Systemic circulation has High resistance
Because of increased smooth muscle in the arterioles & the metarterioles.
Systemic circulation has Low compliance
Because of resistance
offered by the arterioles and the
metarterioles
