The navel, or umbilicus, is the noticeable scar on the abdomen marking the point where the umbilical cord once connected a developing fetus to the placenta. It is a unique anatomical feature that represents the body’s transition from dependence on the mother for sustenance to independent life. The structure signifies the only visible evidence of a former direct connection to an internal system. The small indentation is the external anchor point for several structures that extend deep within the abdominal cavity.
The Umbilical Cord System
During development, the umbilical cord functions as the fetus’s external life support system, facilitating the exchange of nutrients, oxygen, and waste products with the mother’s blood supply through the placenta. The core of this system typically contains three distinct blood vessels wrapped in a protective, gelatinous substance known as Wharton’s jelly. This soft tissue insulates the vessels and provides structural support, preventing them from being compressed.
The blood vessels consist of a single, thinner-walled umbilical vein and two thicker, muscular umbilical arteries. The umbilical vein transports freshly oxygenated, nutrient-rich blood from the placenta directly toward the developing fetus. Conversely, the two umbilical arteries are responsible for carrying deoxygenated, waste-laden blood away from the fetus and back to the placenta for disposal.
Beyond the blood vessels, the cord also contains ducts that relate to the developing urinary and digestive systems. The urachus, which is a canal derived from the allantois, connects the fetal bladder to the cord. Separately, the vitelline duct, or omphalomesenteric duct, briefly links the developing gut tube to the yolk sac. These ducts are present early in development but are expected to close and regress entirely before birth.
The Remnants of the Umbilical Cord
The connection between the navel and the internal organs is not a collection of open tubes but rather a series of dense, fibrous scars known as ligaments, which form shortly after birth. Once the cord is clamped and the newborn takes its first breath, the change in pressure and temperature triggers the blood vessels to constrict and close, halting blood flow. Over a period of weeks and months, the former blood vessels and ducts within the abdomen become involuted, meaning they collapse and transform into non-functional, cord-like ligaments.
The single umbilical vein, which once carried oxygen to the developing liver, collapses to become the Round Ligament of the Liver, also known as the Ligamentum Teres Hepatis. This ligament extends upward from the inner side of the navel and travels superiorly to anchor the liver to the abdominal wall. Its presence is a permanent anatomical marker of the fetal circulation pathway.
The two umbilical arteries, which previously carried waste products away from the fetus, also undergo this fibrous transformation. They become the two Medial Umbilical Ligaments, which course inferiorly from the umbilicus toward the pelvis. These paired ligaments run along the inside of the anterior abdominal wall, helping to anchor structures in the lower abdomen.
The urachus, the structure connecting the bladder in utero, involutes to form the Median Umbilical Ligament. This structure runs down the midline of the abdominal wall from the navel toward the top of the urinary bladder. All of these ligaments serve primarily as anchors and dividers within the abdominal space, permanently connecting the navel to internal organs like the liver and bladder.
Common Health Concerns Related to the Navel
The site of the former umbilical cord insertion remains a relative weak point in the muscular abdominal wall, which can lead to common health issues. The most frequent concern is an umbilical hernia, which occurs when the fibrous ring of muscle and tissue around the navel does not fully close after birth. This patent umbilical ring allows a small portion of the intestine or fatty tissue to push outward, creating a noticeable bulge when pressure is applied, such as during crying or coughing.
While many small umbilical hernias in infants close spontaneously within the first few years of life, some require surgical repair if they are large or persist into childhood. Another common issue is navel infection, or omphalitis, which arises because the deep folds of the umbilicus can trap sweat, dead skin cells, and debris. Poor hygiene in this area can lead to bacterial growth, resulting in discharge, redness, or cellulitis in the surrounding skin.
A rarer condition is a Patent Urachus, which represents a failure of the urachus to fully transform into the median umbilical ligament. This leaves a persistent, open channel that can connect the bladder directly to the navel, sometimes resulting in a continuous or intermittent discharge of urine from the umbilicus. The condition requires attention because it creates an abnormal connection between the urinary tract and the exterior of the body.