Final answer:
The umbilical cord, carrying two arteries and a vein, connects the fetus and placenta, facilitating exchange of nutrients and waste. It is cut after birth to prompt the newborn's breathing, and the leftover stub forms the navel.
Step-by-step explanation:
The umbilical cord is a vital lifeline between the fetus and the placenta, allowing for the transfer of oxygen, nutrients, and waste materials between the mother and the developing baby. This long, narrow conduit contains two umbilical arteries and one umbilical vein, ensuring efficient circulation. During childbirth, as soon as the baby is born, the umbilical cord is double-clamped and cut between the clamps, which is crucial as it prompts the baby to start breathing on their own. After the cord is cut, the baby no longer eliminates carbon dioxide through the placenta, leading to a rise in carbon dioxide levels in the baby's blood and triggering their first breath. The umbilical stub left on the newborn dries and falls off within a few weeks, forming the navel.
The attachment of the umbilical cord is through a process where blood exchanges occur between the fetus and mother. This exchange of substances is facilitated by the placenta, which is attached to the mother's uterus and is connected by the umbilical cord to the fetus. Once the umbilical cord has been cut after birth, the blood vessels in the cord collapse, with the Wharton's jelly within the cord swelling in response to cooler external temperatures, causing the blood vessels to constrict and cease their function.