Functional architecture of the ligamentum arteriosum in adults]

The ligamentum arteriosum was studied in eight normal adult human hearts obtained at autopsy. Four of these hearts were treated by the Zemper method and extensively dissected under a steromicroscope (from X 6 up to X 40); two were embedded in celloidin and sectioned at 100mugm; two were embedded in paraffin and sectioned one 50mugm and the other at 75 mugm. Section were stained by the axan and the resorcin-fuchsin methods. Unstained sections were examined under polarized light.The ligamentum arteriosum may be considered as a small smooth muscle, whose origin is in the arteria pulmonalis sinistra and the insertion in the arcus aortae. Therefore, the ligamentum arterisum may be considered as a myoelastic system, included in a collagenous stroma. Muscle, elastic and collagen fibers present a cross-spiral disposition. Being a myoelastic system with a collagen component, the ligamentum arteriosum cannot be considered as a simple arcus aortae support; it must play some functional role in controlling the arcus aortae curvature during the several different steps of the cardiac cycle.