In the
fetusA fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
, the
ductus venosus shunts approximately half of the blood flow of the
umbilical veinThe umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta to the growing fetus.The blood pressure inside the umbilical vein is approximately 20 mmHg.-Development:...
directly to the
inferior vena cavaThe inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....
. Thus, it allows oxygenated blood from the
placentaThe placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
to bypass the
liverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. In conjunction with the other fetal shunts, the
foramen ovaleThere are multiple structures in the human body with the name foramen ovale :* In the fetal heart, the foramen ovale is a shunt from the right atrium to left atrium....
and
ductus arteriosusIn the developing fetus, the ductus arteriosus , also called the ductus Botalli, is a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled lungs. Upon closure at birth, it becomes the ligamentum arteriosum...
, it plays a critical role in preferentially shunting oxygenated blood to the fetal brain. It is a part of
fetal circulationThe fetal circulation is the circulatory system of a human fetus, often encompassing the entire fetoplacental circulation that also includes the umbilical cord and the blood vessels within the placenta that carry fetal blood....
.
Postnatal closure
The ductus venosus is open at the time of the birth and is the reason why umbilical vein catheterization works. Ductus venosus naturally closes during the first week of life in most full-term neonates; however, it may take much longer to close in pre-term neonates. Functional closure occurs within minutes of birth. Structural closure in term babies occurs within 3 to 7 days.
After it closes, the remnant is known as
ligamentum venosumThe ligamentum venosum is the fibrous remnant of the ductus venosus of the fetal circulation. Usually, it is attached to the left branch of the portal vein within the porta hepatis...
.
If the ductus venosus fails to occlude after birth, the individual is said to have an intrahepatic
portosystemic shuntA portosystemic shunt , also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital or acquired condition....
(PSS). This condition is hereditary in some dog breeds (e.g.
Irish WolfhoundThe Irish wolfhound is a breed of domestic dog , specifically a sighthound. The name originates from its purpose rather than from its appearance...
). The ductus venosus shows a delayed closure in preterm infants, with no significant correlation to the closure of the
ductus arteriosusIn the developing fetus, the ductus arteriosus , also called the ductus Botalli, is a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled lungs. Upon closure at birth, it becomes the ligamentum arteriosum...
or the condition of the infant. Possibly, increased levels of dilating prostaglandins leads to a delayed occlusion of the vessel.