In the

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal dev ...

, the ''ductus venosus'' (Arantius' duct after Julius Caesar Aranzi) shunts a portion of

umbilical vein The umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta into the growing fetus. The umbilical vein provides convenient access to the central circulation of a neonate for restoration of blood v ...

blood flow directly to the

inferior vena cava The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of th ...

. Thus, it allows oxygenated blood from the

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...

to bypass the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it i ...

. Compared to the 50% shunting of umbilical blood through the ''ductus venosus'' found in animal experiments, the degree of shunting in the human fetus under physiological conditions is considerably less, 30% at 20 weeks, which decreases to 18% at 32 weeks, suggesting a higher priority of the fetal liver than previously realized. In conjunction with the other fetal shunts, the ''foramen ovale'' and ''

ductus arteriosus The ''ductus arteriosus'', also called the ''ductus Botalli'', named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus connecting the trunk of the pulmonary artery to the proximal descending aorta. It a ...

'', it plays a critical role in preferentially shunting oxygenated blood to the fetal brain. It is a part of

fetal circulation In humans, the circulatory system is different before and after birth. The fetal circulation is composed of the placenta, umbilical blood vessels encapsulated by the umbilical cord, heart and systemic blood vessels. A major difference between t ...

Anatomic course

The pathway of fetal umbilical venous flow is umbilical vein to left portal vein to ''ductus venosus'' to ''inferior vena cava'' and eventually the right atrium. This anatomic course is important in the assessment of neonatal umbilical venous catheterization, as failure to cannulate through the ''ductus venosus'' results in malpositioned hepatic catheterization via the left or right portal veins. Complications of such positioning can include hepatic hematoma or abscess.

Postnatal closure

The ''ductus venosus'' is open at the time of birth and that is the reason why umbilical vein

catheterization In medicine, a catheter (/ˈkæθətər/) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Cat ...

works. The ''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 venosum The ligamentum venosum, also known as Arantius' ligament, 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. It may be continuous with the ...

''. If the ''ductus venosus'' fails to occlude after birth, it remains patent (open), and the individual is said to have a patent ''ductus venosus'' and thus an intrahepatic

portosystemic shunt A portosystemic shunt or portasystemic shunt (medical subject heading term; PSS), also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital (present at birth) or acquired condition and occ ...

(PSS). This condition is hereditary in some dog breeds (e.g. Irish Wolfhound). The ''ductus venosus'' shows a delayed closure in

preterm infant Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between ...

s, with no significant correlation to the closure of the ''

'' or the condition of the infant. Possibly, increased levels of dilating prostaglandins leads to a delayed occlusion of the vessel.

References

{{Veins Embryology of cardiovascular system Veins