The Umbilical Cord and Embryonic Circulation
The umbilical cord and embryonic circulation are essential for providing nutrients, oxygen, and waste removal between the developing embryo (and later the fetus) and the mother. This system plays a critical role in sustaining the growing embryo during pregnancy, as the placenta acts as the interface for maternal-fetal exchange.
The Umbilical Cord: Structure and Function
The umbilical cord connects the embryo/fetus to the placenta, providing the necessary pathway for the exchange of gases, nutrients, and waste products. It is an essential structure for the survival and development of the fetus.
Structure of the Umbilical Cord:
- Length and Appearance: The umbilical cord typically measures about 50 to 60 cm in length and 1-2 cm in diameter at full term, though it can vary. The cord is typically coiled and contains several distinct components.
- Three Main Vessels:
- Two Umbilical Arteries: These arteries carry
deoxygenated blood from the fetus to the placenta. They originate from the internal iliac arteries of the fetus and travel along the cord to the placenta.
- One Umbilical Vein: The vein carries oxygenated, nutrient-rich blood from the placenta back to the fetus. This vein travels through the umbilical cord to the fetus, entering the abdomen and then dividing into smaller vessels within the liver and the inferior vena cava.
- These three vessels are surrounded by Wharton's jelly, a gelatinous substance that provides structural support to the blood vessels, preventing cord compression and protecting the vessels from external pressure.
- Other Components:
- Amniotic Membranes: The cord is enveloped by a layer of amnion (one of the membranes of the amniotic sac), which protects the vessels from mechanical damage.
- Placental End: At the placental end, the vessels branch out and interconnect with the blood vessels of the placenta. This is where maternal-fetal exchange occurs.