The umbilical cord is a pretty amazing structure. In the developing fetus
, it goes from the placenta
) of the mother, through the baby's navel
and into the fetal liver
. This is how oxygen
and nutrients are conveyed into the growing fetus.
If the baby's blood pressure
gets too high, small blood vessles around the umbilical cord expand and cause the abdominal wall
to spread. This then allows two arteries
that run from the fetal aorta
by way of the bladder
to conduct excess blood back to the placenta. All of these blood vessels are usually still open at the time of birth and tubes may be inserted into them to reach the circulatory system or the heart for measuring blood pressure or obtaining blood samples.
Another passage leaves the bladder and goes out the navel, allowing the developing fetus to expel urine
. This eventually shrivels into a ligament
connecting the bladder to the abdominal wall after birth. In some cases, this passage may still be open at the time of birth, allowing the baby to expel urine through an open navel.
Even in adults, the lumen
of the umbilical vein
does not completely disappear and sometimes, it may be opened in order to inject chemotherapeutic drugs