Saturday, May 23 (2020); Respiratory system
The pulmonary circulation is a low pressure, low resistance system, and it contains much less blood than the systemic circulation (500ml vs. 4500ml). Where the systemic arterioles would vasodilate (eg. hypoxia, hypercapnia), the pulmonary arteries will do the opposite and vasodilate. The blood flow in the systemic circulation is distributed regionally according to organ system demands, using resistance arterioles to redistribute blood flow, whereas in the lung there nothing of the sort, and it can barely redistribute blood flow away from hypoxic regions. In short, the pulmonary and systemic circulatory systems are vastly different.