The ligamentum arteriosum is a piece of fibrous tissue that develops from the ductus arteriosus (DA). It takes shape within three weeks of a person's birth and remains a feature in the normal adult heart. The term ligamentum arteriosum is the Latin phrase for the arterial ligament.
Some people describe the ligamentum arteriosum as a non-functional bit of the ductus arteriosus after embryonic formation. Others, however, cite the vestige as contributing to the rupture of the aorta — the body's largest artery — during major trauma. This is because it keeps the artery in place when it springs back to its original position during a rapid deceleration. As a result, the aorta may break open.
During prenatal development, the heart of the fetus has a small hole or passage called the ductus arteriosus. Also called the ductus Botalli, it connects the pulmonary artery, which transports deogygenated blood from the heart to the lungs and the area of the aorta, referred to as the aortic arch. In the fetus, however, the DA is meant for permitting a significant amount of blood from the heart's right ventricle to pass around the fluid-filled lungs.
Within 12 to 24 hours after birth, however, the DA begins to close — a process that is typically completed within three weeks. The ligamentum arteriosum is what is left after this closure, and is connected to the the aortic arch and the pulmonary artery. The pulmonary artery is located to the arterial ligament's inferomedial, or lower middle, area. The aortic arch is posterosuperior to the ligament, or located at its back and above it.
Lateral to the tissue is the vagus nerve, which is the 10th of the 12 paired cranial nerves. For this reason, it is also called cranial nerve X. Also lateral to the vestige is the recurrent laryngeal nerve, or Galen's nerve, that springs from the vagus nerve on the left. The laryngeal nerve hooks around the ligament from the rear where part of the aorta is located, then it goes up to the voice box after which it is named.
Anteriorally, or frontally, the ligamentum arteriosum is near the surface of a network of nerves that innervate the heart from its base. The tangle is called the cardiac plexus. Also to the front of the ligamentum arteriosum is the phrenic nerve, which mainly emerges from the fourth cervical nerve (C4).