The umbilical cord—consisting of one large vein and two smaller arteries—forms very early in pregnancy and serves to shuttle oxygenated blood from the mother to the baby and deoxygenated blood and waste from the baby to the mother. The umbilical vein carries oxygenated blood from the placenta to the fetus, and the umbilical arteries carry deoxygenated, nutrient-depleted blood from the fetus to the placenta. Shortly after birth, the umbilical cord is clamped and cut leaving us with a constant reminder of the nourishment we received from our mother in the form of a belly button (also called the umbilicus or navel).
Once cut, the exterior remnant of the umbilical cord withers away and turns into a firm stump until it falls off. But what about the blood vessels that once exchanged blood between mother and baby behind the belly button? The part of the blood vessels closest to the belly button degenerates into a ligament called the round ligament. This ligament extends from the belly button to the porta hepatis—a deep fissure on the surface of the liver where neurovascular structures (except the hepatic veins) and hepatic ducts enter and leave the liver—where it joins with the ligament vernosum (the fibrous remnant of fetal circulation) to separate the left and the right lobes of the liver. The round ligament contains some small veins, called paraumbilical veins, which can expand when high pressure occurs in the veins around the abdominal organs.
Two additional ligaments are formed from the remnants of the umbilical cord behind the belly button. The medial umbilical ligament runs from the belly button to the liver and contains the obliterated arteries of the umbilical cord, whereas the median umbilical ligament is formed from the veins. Essentially, the inside of the umbilical cord behind the belly button degenerates into connective tissue and becomes a vestigial remnant.
Recently, essential oil users have adopted a technique used by cannabis users called the Pechoti method and administered essential oils through the belly button. This method is commonly used among cannabis users to absorb CBD and THC into systemic circulation. The claim is there is a gland called the Pechoti gland behind the belly button that houses more than 72,000 veins and millions of nerves. When substances are applied in or on the belly button, this gland distributes the substances into systemic circulation. However, the existence of the Pechoti gland is not accepted in science and there isn’t any actual evidence to suggest this gland is present.
Essential oils rely on entrance into systemic circulation through capillaries (the smallest blood vessels in the body that are only one endothelial cell thick) not veins. Since the belly button does not have a noteworthy capillary supply, it is not likely that essential oils will enter systemic circulation via this route. Instead, you are more likely to experience a localized effect to the abdominal region. There are however some capillaries within the abdominal region, so it is possible small amounts of essential oil may enter systemic circulation.
A more practical approach for systemic circulation is to take the essential oils in a capsule or sublingually. This method will result in more essential oil reaching systemic circulation. So, for now, this method seems to be more myth than reality.