From what does the umbilical cord develop, and over what timeframe?

The umbilical cord develops between weeks 4-8 of gestation and contains remnants of the yolk sac and allantois.

It comes to contain two arteries and one vein within Wharton's jelly, connecting the fetus to the placenta and carrying the fetal-placental circulation.

Clinical relevance. Knowing cord embryology explains its normal structure and the origin of cord abnormalities.

More Detail

Development of the umbilical cord

The cord forms early in embryogenesis from extra-embryonic structures.

Origin and timing

• Develops between weeks 4-8 of gestation.
• Contains remnants of the yolk sac and allantois (the allantois contributes to the umbilical vessels).

Final structure

• Mature cord: two umbilical arteries and one umbilical vein.
• Vessels embedded in Wharton's jelly (mucoid connective tissue) that protects them from compression.
• Connects the fetus to the placenta, carrying deoxygenated blood to the placenta (arteries) and oxygenated blood back to the fetus (vein).

Significance

Early developmental disturbances can produce cord abnormalities (e.g. single umbilical artery), and the yolk-sac/allantois remnants explain occasional cord cysts/remnants.