Ligamentum Arteriosum,ductus Arteriosus: Anatomy,function - Kenhub

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Ductus arteriosus

Aortic arch Arcus aortae 1/3 Synonyms: Arch of aorta

The fetal ductus arteriosus arises from the distal left portion of the sixth aortic arch or the descending aorta. This short artery (8-12mm) forms a connection between the pulmonary trunk, at the point of its division into the right and left pulmonary arteries, and the inferior part of the aortic arch, in line with the origin of the left subclavian artery. The ductus arteriosus location in fetal circulation allows to bypass the pulmonary circuit, which is not needed as oxygenated blood is delivered via the umbilical vein. That means that ductus arteriosus is essentially the connection between the right ventricle and the descending aorta.

It is suggested that the receptors in the walls of the ductus arteriosus react to oxygen causing the walls to contract. However, in an unborn fetus, these receptors are inhibited by prostaglandins E2, I2 and F2a, thereby keeping it open. After birth, this inhibition ceases while a substance called bradykinin is released from the lungs during the first inspiration. Both of these factors result in the contraction of the circular muscle in the tunica media of the vessel’s wall. This process is known as functional closure; it closes off the blood flow which happens up to 48 hours after birth. It occurs alongside other processes, such as closure of the foramen ovale, umbilical vessels and the ductus venosus, all related to changes in the circulation of a newborn. Anatomic closure occurs gradually in the following 1-3 months by the means of thickening of the tunica intima, the innermost layer of the vessel. In short, this means that no more blood is physically able to enter the ductus arteriosus and it begins to gradually break down.

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