Synonyms in a broader sense
Lungs, alveoli, bronchi Medical: Pulmo
Pulmonary circulation
In pulmonary perfusion, the lung is supplied with blood by two functionally different vessels that originate from the small and large body circulation. In pulmonary circulation, the vessels of the small circulation (pulmonary circulation) transport the entire blood volume of the body through the lungs to absorb new oxygen. They serve the entire body and are also called vasa publica (public vessels).
The vessels of the great circulation (body circulation) in pulmonary circulation are only responsible for supplying oxygen to the lung tissue. Therefore they are also called vasa privata (own vessels). All the following characteristics refer to the blood flow in the vessels of the small circulation, which are much more important for the function of the lungs.
Basically, it must be said that the control of the pulmonary blood flow in the pulmonary vessels is not, as is so often the case, based on the blood pressure prevailing there. This makes sense, considering that the incoming blood should be available for the large circulation as quickly as possible. Instead, another mechanism is used for regulation: hypoxic vasoconstriction.
This means that the oxygen content of the pulmonary alveoli determines the extent of blood flow. The more oxygen, the more blood flows through this section; the less oxygen (hypoxia), the less blood (vasoconstriction). This mechanism is mediated by proteins of the cell wall (potassium ion channels) of the pulmonary alveoli, which change their shape when the oxygen content increases, thus initiating a contraction, i.e. narrowing of the vessels.
Assume that an air-conducting section is completely blocked by a foreign body. This means that fresh air can no longer reach the alveoli. The blood flowing through these alveoli would not be able to absorb fresh oxygen.
This old blood would still be pumped through the body, but without transporting oxygen. This scenario is avoided by hypoxic vasoconstriction. The blood pressure in the pulmonary vessels is low (only 1⁄4 of the pressure in the main artery (aorta)).
This prevents the high pressure from pressing fluid from the smallest blood vessels (capillaries) into the pulmonary alveoli. If this does happen, fluid collects in the lungs (pulmonary edema). Common causes of pulmonary edema are weakness of the left heart pump (left heart failure), an increased amount of blood, pneumonia caused by pathogens or an obstruction of a larger vessel in the lung (pulmonary embolism). The danger of pulmonary edema is that the distance for the gas to be exchanged from the pulmonary alveoli during pulmonary perfusion to the vessels and back is increased. The leading sign of pulmonary edema is shortness of breath (dyspnoea).
