The lung is supplied by pulmonary and bronchial arteries. Unilateral ligation of a main pulmonary artery results in bronchial vascular expansion and new anastomoses between the bronchial and pulmonary circulations. The form and location of this expansion is the subject of this project.

We ligated the left pulmonary of 15 rats and killed 3 rats 1,2,4, 6, and 8 weeks after the ligation. We studied 3 control animals that did not undergo ligation. We cast the vasculature of the lungs with methyl methacrylate and examined both the right and left lungs by light and scanning electron microscopy.

We found that the expansion and anastomoses occurred in and near the bronchovascular bundles and along the pleura, even though the rat pleura is supplied by pulmonary vessels. Near large pulmonary arteries, the junctional and alveolar capillaries were irregular, flattened, and had lateral outbulgings. The diameters varied within short lengths.