Ductus Arteriosus, Ductus Venosus, And Foramen Ovale in the Fetal Heart Circulation
In this quick easy lesson, we explain the main functions and purposes of the 3 shunts in fetal circulation: ductus arteriosus, ductus venosus, and foramen ovale, how these fetal heart structures close, and their medical significance and complications in the fetal heart: Ductus Arteriosus vs Foramen Ovale vs Ductus Venosus
What are the 3 Shunts in Fetal Circulation?
The 3 main shunts in fetal circulation are ductus arteriosus, ductus venosus, and foramen ovale. The general purpose of these 3 shunts is to divert blood and nutrients efficiently for the fetus, including its fetal heart and body.
- Ductus Arteriosus: Ductus arteriosus is a shunt in fetal circulation that diverts blood from the pulmonary artery directly to the aorta, instead of the lungs.
- Ductus Venosus: Ductus venosus is another shunt in fetal circulation that diverts oxygen-rich blood directly from the umbilical vein to the inferior vena cava and fetal heart. The ductus venosus bypasses the liver.
- Foramen Ovale: Foramen ovale is a shunt for fetal circulation in order to divert blood directly from the right atrium to the left atrium. Because the fetus is receiving oxygen directly from the mother via the umbilical vein, the fetus’s lungs are not working actively while utero. The foramen ovale thus is a fetal structure shunt to enhance efficiency of blood flow, bypassing the lungs.
What is the function of Ductus Arteriosus?
The ductus arteriosus is found in a fetal heart and provides a direct opening from the pulmonary artery to the aorta. Because the fetal lungs do not work and it receives oxygenated blood from the mother, blood can pass directly from the pulmonary artery (which leads to the lungs) into the aorta to be pumped to the rest of the body. The blood that leaks into the right ventricle after most of it passes from the right atrium to the left atrium through the foramen ovale is pumped into the pulmonary artery directly into the aorta through the ductus arteriosus.
What happens to the Ductus Arteriosus after birth? What closes the ductus arteriosus?
After birth, the ductus arteriosus is “pushed” closed by the lung’s need for blood flow through the pulmonary arteries and into working lungs. The sudden increase of partial pressure of oxygen in the air causes the baby to take its first breath, and cause the muscular wall of the ductus arteriosus to close abruptly. The closure of the ductus arteroisus is important in order to prevent oxygen-poor blood from the pulmonary artery to mix with the aorta’s oxygen-rich blood. If the ductus arteriosus does not close, then the connection between the pulmonary artery and aorta remains, and the baby has Patent Ductus Arteriosus, a congenital heart defect.
How long does it take for the ductus arteriosus to close?
Research reports that it takes approximately 2 to 3 days for the ductus arteriosus to close for the average baby (Medscape), and can even close as early as 15 hours. For some babies, by their 3rd month of life, the ductus arteriosus is finally closed. If the ductus arteriosus does not close soon, the baby may suffer from Patent Ductus Arteriosus. Premature babies are at a higher risk of developing patent ductus arteriosus because it takes the connection between the pulmonary artery and aorta longer to close.
What is the Remnant of the Ductus Arteriosus Called?
The remnant of the ductus arteriosus is called the ligamentum arteriosum. The ligamentum arteriosum is a small ligament that attaches to the end of the aortic arch and the first part of the descending aorta. Research studies have also discovered postanatomical changes as the person grows older, such as calcification of the ligamentum arteriosum. There is no longer a function of the ligamentum arteriosum because it is now a vestige of the fetus’s ductus arteriosus.
What is the Foramen Ovale?
In a fetus, the foramen ovale provides a shortcut for blood flow in the heart. Because the fetal lungs do not work, and the fetus receives its oxygen from the mother through the umbilical vein, the blood entering the right side of the heart already contains oxygen. Thus, it does not need to be pumped to the right ventricle to the pulmonary artery, lungs, and pulmonary vein. Instead, the foramen ovale allows an opening in which the blood can pass directly from the right atrium and into the left atrium. After birth, the infant’s foramen ovale will close and remain as a thin ligament between the atria.
What happens if the foramen ovale fails to close?
The foramen ovale usually takes about 6 months to close, but sometimes, the foramen ovale fails to close. If the foramen ovale fails to close, the baby has Patent Foramen Ovale (PFO), which is a congenital heart defect. Patent foramen ovale usually does not cause symptoms for newborns. Only in serious patient cases, patent foramen ovale caused by an unclosed foramen ovale can increase a patient’s risk for stroke and blood clots.
- Anatomy, Thorax, Heart Ductus Arteriosus https://www.ncbi.nlm.nih.gov/books/NBK470160/
- Mayo Clinic. Patent ductus arteriosus. https://www.mayoclinic.org/diseases-conditions/patent-ductus-arteriosus/symptoms-causes/syc-20376145
- Heart Blood Flow 14 Steps: https://moosmosis.org/2018/10/19/circulatory-system-blood-flow-pathway-through-the-heart/