V-shaped cushion at the origin of bovine pulmonary supernumerary arteries:structure and putative function

This study investigates the anatomic structure at the origin of pulmonary s upernumerary arteries and their parent conventional artery. Histological ex amination showed that at the origin of each supernumerary artery the wall o f the parent conventional artery is organized into a distinct V-shaped stru cture, which begins on the hilum side of each supernumerary artery as a fun nel-shaped channel running into the supernumerary artery. The base of the c hannel is particularly thin walled. The lateral walls of the channel are co mposed of musculoelastic cushions that become more pronounced toward the su pernumerary artery and fuse on its distal side, forming a baffle that proje cts over the supernumerary artery lumen. These V-shaped structures/cushions were observed with video stereo dissecting microscopy in both an open and closed state in isolated arteries in vitro. Pulmonary vasoconstriction of i solated arteries with the thromboxane A(2) mimetic U-46619 increased the nu mber of V-shaped structures in the closed state. These studies indicate the presence of a novel anatomic structure at the origin of pulmonary supernum erary arteries, which may be able to regulate blood flow into the supernume rary artery.