Close-up, Umbilical Cord at 7½ Weeks

7 weeks, 4 days

The coiled umbilical cord contains one vein and two arteries. Arteries always carry blood away from the heart, while veins return blood to the heart.

Note the brighter red color of the umbilical vein, reflecting its cargo of oxygenated blood that is returning from the placenta.

1. umbilical vein

2. vitelline vessels (yolk stalk)

3. umbilical arteries

4. placental vessels

All ages referenced to fertilization, not last menstrual period.