The ductus arteriosus is an essential vessel within the fetal circulation:
- it extends from the distal part of the pulmonary trunk superolaterally to the inferior surface of the aorta at a site that is distal to the origin of its first three main branches
- it conveys deoxygenated blood from the right ventricle to the aorta and thence to the umbilical arteries within the placenta
- hence, it short-circuits the lungs and instead permits reoxygenation of blood via the placenta
- in normal development, the ductus forms the ligamentum arteriosum
More details are given in the section on patent ductus arteriosus.