How is the heart involved in pulmonary circulation?

Answer 1

Right side of the heart is involved in pulmonary circulation. This circulation is called, at times, as lesser circulation, as against the greater or systemic circulation. Blood that flows through the lesser and greater circulation is same in amount. But there is gross difference between the two. You have interstitial compartment in the systemic circulation. This is maintained through high blood pressure there. You do not have the same in pulmonary circulation. What you need here is simple blood flow, with out formation of the interstitial compartment. For that you have blood systolic blood pressure of about 25 mm of Mercury. The blood pressure in the capillaries is about 15 mm of the mercury. The oncotic pressure of the blood proteins is about 22 mm of mercury. So very little fluid is leaked out to keep the alveoli wet. Some times in diseased condition more fluid is leaked out in the alveoli, to give rise to pulmonary oedema.