What Is Your Belly Button Connected to on the Inside?

Your belly button is anchored to a set of fibrous cords and ligaments on the inside of your abdominal wall, all of which are remnants of the blood vessels and ducts that once kept you alive in the womb. During fetal life, the umbilical cord carried blood between you and the placenta through two arteries and one vein. After birth, those vessels collapsed and hardened into tough bands of connective tissue that still physically tether your navel to your liver and the top of your bladder. The story of what sits behind your belly button is really the story of what used to be there and what it turned into.

What the Umbilical Cord Actually Carried

Before birth, the umbilical cord was a coiled, tube-like conduit connecting you to the placenta. By about the twelfth week of pregnancy, the cord had settled into its final form: two arteries and a single vein, all cushioned in a protective jelly-like substance called Wharton’s jelly.¹ These vessels worked in a way that surprises most people. The vein carried oxygen-rich blood from the placenta to the fetus, while the two arteries carried oxygen-depleted blood back to the placenta. That is the reverse of how veins and arteries typically function in your body after birth.²

The volume of blood flowing in each direction was roughly equal, keeping the fetus in a closed circulatory loop with the placenta. Blood velocity in the umbilical vein ranged from about 10 to 22 centimeters per second, and the vein itself was about 30 percent larger in cross-section than the two arteries combined.² The coiled shape of the arteries also played a role in regulating temperature: the helical structure helped transfer heat between the warmer arterial blood leaving the fetus and the cooler venous blood returning from the placenta, contributing to fetal heat regulation.³

What Happens When the Cord Is Cut

The moment the umbilical cord is clamped and severed at birth, a rapid shutdown begins. The two umbilical arteries contain high levels of proteins called proteoglycans in their walls, which allow them to clamp down and close off almost immediately, preventing blood loss from the newborn.⁴ Over the following days and weeks, the short stump of cord left attached to the baby dries out and falls off, leaving behind the scar we know as the belly button.

But the vessels inside do not simply vanish. They undergo a transformation. The blood that once flowed through them is replaced by scar-like fibrous tissue as the vessels close permanently. What were once living, pulsating blood conduits become tough, rope-like ligaments embedded in the inner surface of your abdominal wall. These ligaments persist for the rest of your life, and they are the main structures your belly button is connected to on the inside.

The Connection to Your Liver

The single umbilical vein, which carried oxygenated blood from the placenta into the fetal body, entered through the belly button and traveled upward to the liver. After birth, this vein collapses and becomes a dense fibrous cord called the round ligament of the liver, or ligamentum teres hepatis. You can trace its path from the inner surface of your navel upward along a fold of tissue called the falciform ligament, which attaches to the underside of the liver between its right and left lobes.⁵

This ligament is one of the most direct physical connections between your belly button and an internal organ. It is not functional in the way it once was, but it is still a real piece of anatomy. Surgeons routinely encounter it during abdominal procedures, and it serves as a reliable anatomical landmark for identifying the division between the liver’s lobes.

Tucked alongside the round ligament, within the free edge of the falciform ligament, are small paraumbilical veins.⁵ These tiny veins are normally insignificant, but they become clinically relevant when liver disease raises pressure in the portal venous system. In that situation, blood gets rerouted through these paraumbilical veins, causing them to swell and become visible on the surface of the abdomen around the navel. The resulting pattern of dilated veins radiating outward from the belly button is called caput medusae, and it is a classic sign of portal hypertension seen in conditions like cirrhosis.⁶ The name comes from Medusa of Greek mythology, whose head was covered in snakes. It is a dramatic reminder that the old vascular highway between the belly button and the liver never fully disappears.

The Connection to Your Bladder

Running downward from the belly button toward the pelvis is another fibrous remnant, this one connecting to the top of the urinary bladder. During fetal development, a tube called the urachus carried urine from the fetal bladder out through the umbilical cord and into the amniotic fluid. After birth, this tube normally seals off and becomes a thin fibrous cord called the median umbilical ligament, stretching from the bladder’s apex up to the inner surface of the navel.⁷

On either side of the median umbilical ligament, two more fibrous cords run in roughly the same direction. These are the medial umbilical ligaments, the remnants of the two umbilical arteries that once carried deoxygenated blood from the fetus back to the placenta. Together, these three cords fan out from the back of the belly button like the spokes of a wheel pointing downward and to the sides, all covered by a layer of the tissue lining the abdominal cavity. You would see them clearly if you looked at the inner surface of the lower abdominal wall during surgery.

The architecture around the belly button itself is more complex than most people realize. The ligaments attach to a fibrous ring embedded in the abdominal wall, and the precise pattern of how they insert into that ring varies from person to person. Researchers who have dissected these structures have classified the umbilical ring into at least five types based on the shape and attachment pattern of the surrounding ligaments. The way the round ligament inserts at the ring’s lower border, along with a layer of fascial tissue, appears to provide structural reinforcement that helps prevent umbilical hernias.⁸

When the Urachus Does Not Fully Close

In most people, the urachus completely seals off before or shortly after birth and is never noticed again. But in a small number of people, parts of this tube remain open, leading to what are broadly called urachal anomalies. There are four recognized types: a patent urachus, where the entire tube remains open from bladder to belly button; a urachal sinus, where only the belly-button end stays open; a urachal diverticulum, where only the bladder end stays open; and a urachal cyst, where both ends seal but a fluid-filled pocket persists in the middle.⁹

Urachal cysts are the most common of the four. They often go unnoticed for years until they become infected, at which point they can cause abdominal pain, fever, nausea, and urinary symptoms.⁹ A patent urachus, where the channel is fully open, is much rarer. One estimate puts the incidence at roughly 1 in 70,000 people. Patent urachus is typically diagnosed in infancy when urine drains from the belly button, but it can go undetected into adolescence or adulthood. In one reported case, a 17-year-old had a patent urachus that only became apparent after a belly button piercing was removed, which effectively completed the channel to the skin surface and caused a sudden leak.¹⁰ The standard treatment for patent urachus is surgical removal, partly because of a small risk of malignant change over time.¹⁰

If you ever notice persistent clear or cloudy fluid leaking from your belly button, especially if it smells like urine or is accompanied by redness and pain, a urachal remnant is one of the things a doctor would consider. Most people go their whole lives without knowing the urachus ever existed, but for the unlucky few whose version did not fully close, it can become a genuine medical issue.

Another Fetal Remnant Near the Navel

The urachus is not the only fetal structure that occasionally persists near the belly button. During early development, the yolk sac connects to the fetal gut through a channel called the vitelline duct. This duct normally disappears by about the fifth week of fetal development. When it does not fully close, the result can be a Meckel’s diverticulum, a small pouch protruding from the wall of the small intestine.¹¹ This is the most common congenital abnormality of the gastrointestinal tract and is typically found about two feet upstream from where the small intestine meets the large intestine. It usually causes no symptoms and is discovered incidentally during surgery for something else. In rare cases, though, it can bleed, become inflamed (sometimes mimicking appendicitis), or form a connection to the navel.

Why Surgeons Pay Attention to the Belly Button

From a surgical standpoint, the belly button is one of the most useful spots on the abdomen. The navel sits at a natural thin point in the abdominal wall where the fibrous remnants converge, and this makes it a convenient entry point for laparoscopic surgery. Single-incision laparoscopic procedures, where the surgeon operates through a single small cut, frequently use the belly button as the access site because the resulting scar is largely hidden by the navel’s natural folds.⁸ This is also why understanding the ligaments and fascial layers behind the navel matters practically: a surgeon entering through the belly button needs to know exactly where the round ligament, the median umbilical ligament, and the paraumbilical veins sit to avoid damaging them.

In cosmetic surgery, particularly after abdominoplasty (a tummy tuck), the belly button often needs to be reconstructed or repositioned. Surgeons recreate its depth and shape by anchoring the skin to the underlying fascial layer with sutures placed at specific clock positions around the umbilical stalk.¹² The fact that the belly button is more than a surface marking and has a genuine structural anchor beneath it is what makes this kind of reconstruction possible.

Umbilical Endometriosis

One of the more unusual conditions that can affect the belly button is primary umbilical endometriosis, in which tissue resembling the uterine lining grows at or near the navel. This is rare and unrelated to the fetal remnants discussed above. It typically presents as a painful, discolored nodule in or around the belly button that may swell or bleed cyclically with menstrual periods.¹³ Because it is uncommon and the symptoms can mimic other conditions like a hernia or an infected cyst, it is frequently misdiagnosed or diagnosed late. Treatment usually involves surgical excision of the affected tissue.

The Belly Button’s Microbial Ecosystem

Setting aside what the belly button connects to structurally, the navel is also a surprisingly rich habitat for bacteria. A study that sampled the belly buttons of dozens of volunteers found, on average, 67 distinct types of bacteria per navel. The overall diversity was at least as high as what researchers find on other areas of skin. Despite all that variety, the communities were dominated by just a handful of species: only six bacterial types showed up in more than 80 percent of the people sampled, and those six accounted for roughly a third of all the bacteria present.¹⁴ The warm, sheltered, slightly moist environment of the navel makes it an ideal pocket for microbial colonization. This is harmless for the vast majority of people, but it does explain why belly buttons can occasionally develop minor infections or produce an odor, particularly “innies” with deeper recesses that trap moisture and dead skin cells.

Fetal Medicine and the Umbilical Cord

Before birth, the umbilical cord is not just a passive supply line. It is also a point of medical access. A procedure called cordocentesis, or percutaneous umbilical blood sampling (PUBS), involves inserting a needle through the mother’s abdomen and into the umbilical cord under ultrasound guidance to obtain a sample of fetal blood. It remains the only procedure that provides direct access to fetal circulation.¹⁵ It can be used to diagnose blood disorders, congenital infections, and certain metabolic conditions. The same access point can also be used therapeutically: in cases of severe anemia caused by blood-type incompatibility between mother and fetus, doctors can perform transfusions directly into the umbilical vein.¹⁶ The procedure carries real risks, including preterm labor and fetal bleeding, so it is reserved for situations where less invasive testing cannot provide the needed information.

Dinosaurs Had Belly Buttons Too

If you have ever wondered whether belly buttons are unique to humans or even to mammals, the answer is no. Any animal that develops inside an egg or a uterus with an umbilical connection to a yolk sac or placenta will have some kind of navel scar. In most reptiles and birds, this scar fades within days or weeks of hatching. But in 2022, researchers described an exceptionally well-preserved fossil of Psittacosaurus, a small dinosaur that lived over 100 million years ago, which still showed a visible umbilical scar on its belly. The scar had persisted at least until the animal reached sexual maturity, making it the oldest known preserved belly button in any egg-laying land vertebrate.¹⁷ The researchers noted that this long-lasting scar most closely resembled what is seen in some modern lizards and crocodilians, though they cautioned that not all dinosaur species necessarily had persistent scars.

The finding is a useful reminder that the belly button is not an arbitrary mark. It sits at the site of the body’s original lifeline, and the underlying anatomy, whether fibrous remnants in a human or a fading scar on a hatched reptile, reflects the universal challenge of nourishing a developing embryo and then cleanly severing that connection at birth.

1
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2
PubMed Central. The Development of the Umbilical Vein and Its Anatomical and Clinical Significance
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PubMed Central. A computational fluid dynamics modelling of maternal-fetal heat exchange and blood flow in the umbilical cord
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PubMed Central. Severing umbilical ties
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PubMed. Anatomy, Abdomen and Pelvis: Falciform Ligament
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PubMed Central. Caput medusae sign; a unique finding during abdominal examination in patients with portal hypertension; case report
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PubMed Central. An Adult with a Remnant Urachus Anomaly Diagnosed in the Emergency Department
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The American Surgeon™. Surgical Anatomy and Morphologic Variations of Umbilical Structures
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PubMed Central. Infected urachal cyst presenting as acute abdomen – a case report
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BMJ Case Reports. Belly button piercings: a saving grace? A patent urachus presenting in a 17-year-old girl
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PubMed Central. Meckel’s diverticulum-Revisited
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Revista Brasileira de Cirurgia Plástica. Omphaloplasty: back to the natural process
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PubMed Central. Primary umbilical endometriosis: a cause of a painful umbilical nodule
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PubMed Central. A jungle in there: bacteria in belly buttons are highly diverse, but predictable
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PubMed Central. A Review of Cordocentesis: Percutaneous Umbilical Cord Blood Sampling
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PubMed. Percutaneous umbilical blood sampling and umbilical vein transfusions. Rapid serologic differentiation of fetal blood from maternal blood
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PubMed Central. Oldest preserved umbilical scar reveals dinosaurs had ‘belly buttons’