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How does the umbilical cord connect the fetus to the placenta?

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Fetal growth — human development Growth of the human fetus from the fourth month to the ninth month of pregnancy.

The umbilical cord is a narrow tissue structure that connects the fetus to the placenta, serving as the vital link for nutrient, gas, and waste exchange.12

The cord contains three primary blood vessels: two umbilical arteries and one umbilical vein. These vessels facilitate a continuous circuit between the fetal and maternal systems:1

Umbilical Vein: Carries oxygenated, nutrient-rich blood from the placenta to the fetus.13
Umbilical Arteries: Carry deoxygenated blood and fetal waste products from the fetus back to the placenta for processing by the maternal circulatory system.12

At the placental end, the umbilical arteries branch into smaller vessels that penetrate the villi. Here, fetal blood comes into close proximity with maternal blood, allowing for the diffusion of oxygen and nutrients into the fetus and the removal of carbon dioxide and nitrogenous wastes, without the two bloodstreams directly mixing. The purified blood is then collected into fetal veins, which converge to form the umbilical vein, returning the blood to the fetus.2