The Umbilical Cord
Definition
A conduit between the developing fetus and the placenta.
50 cm long 2 cm in diameter
Physiologically and genetically part of the fetus
The umbilical vein supplies the fetus with oxygenated, nutrient-rich blood from the placenta.
Conversely, the fetal heart pumps deoxygenated, nutrient-depleted blood through the umbilical arteries back to the placenta.
Development and composition
Develops from and contains remnants of the yolk sac and allantois
It forms in fifth week replacing the yolk sac as the source of nutrients for the fetus
Joins the placenta
Placenta transfers nutrients from the mother's blood without direct mixing..
has an outer layer consisting of circularly arranged smooth muscle cells and an inner layer which shows rather irregularly and loosely arranged cells embedded in abundant ground substance
The umbilical cord contains Wharton's jelly - a mucopolysaccharide which protects the blood vessels inside.
It contains one vein, - carries oxygenated, nutrient-rich blood to the fetus,
and two arteries that carry deoxygenated, nutrient-depleted blood .
Connection to fetal circulatory system
The umbilical cord enters the fetus via the abdomen
After separation entry point will become the umbilicus.
Within the fetus, the umbilical vein continues towards the transverse fissure of the liver, where it splits into two. One branch joins the hepatic portal vein, which carries blood into the liver.
The second branch (the ductus venosus) bypasses the liver and flows into the inferior vena cava,
The two umbilical arteries - from the internal iliac arteries, and pass on either side of the urinary bladder into the umbilical cord
Physiological postnatal occlusion
The umbilical cord occludes physiologically shortly after birth
Collapse of Wharton's jelly
Vasoconstriction of the blood vessels by smooth muscle contraction.
The umbilical vein and ductus venosus close up, and degenerate into fibrous remnants known as the round ligament of the liver and the ligamentum venosum respectively.
Part of each umbilical artery closes up - medial umbilical ligament, while the remaining sections are retained as part of the circulatory system.
Applied Anatomy
A knotted cord
Nuchal cord (cord around neck)
