The umbilicus, commonly known as the belly button, is the scar remaining after the detachment of the umbilical cord at birth. Many people wonder what major organ lies directly behind this central point, but the answer is not a single, fixed organ. The area behind the umbilicus is a dynamic space within the abdominal cavity, separated from the exterior by several layers of tissue.
Anatomy of the Abdominal Wall
The immediate structures behind the skin are layers of the abdominal wall providing support and protection. Moving inward, a layer of subcutaneous fat is encountered, followed by a fibrous sheet of tissue known as fascia. This fascia covers the muscular layer, which includes the strong, vertical rectus abdominis muscles. At the midline, the two rectus muscles are separated by the linea alba, a fibrous band that is relatively thin directly behind the umbilicus. These layers, rather than a solid organ, constitute the physical barrier at the center of the abdomen.
Structures Left Over From Fetal Development
The region deep to the abdominal wall contains several non-functional, fibrous cords that are remnants of fetal structures. The single median umbilical ligament extends from the bladder up to the umbilicus; it is the remnant of the fetal urachus, which connected the bladder to the umbilical cord. Flanking this central structure are two medial umbilical ligaments, remnants of the umbilical arteries that carried deoxygenated blood back to the placenta.
A third fibrous cord, the round ligament of the liver, also converges toward the umbilicus. This cord is the remnant of the fetal umbilical vein, which carried oxygenated blood from the placenta to the liver. These ligamentous remnants serve as anatomical landmarks and contribute to the structural organization of the inner abdominal wall.
The Role of the Small and Large Intestines
The space posterior to the abdominal wall and its fibrous remnants is occupied by the intestines. Loops of the small intestine, specifically the jejunum and ileum, commonly fill the central abdominal space behind the umbilicus. The transverse colon, a segment of the large intestine, also crosses the upper abdomen and can be located near the umbilicus.
The position of these intestinal loops is highly variable and changes constantly with posture and digestion. Because the intestines are not fixed in a single spot, no specific organ is permanently “behind” the belly button. Major blood vessels, such as the aorta and inferior vena cava, are located much deeper, positioned against the spinal column. The intestines are surrounded by the peritoneum, a thin membrane lining the abdominal cavity.
Why the Umbilicus Area Is Prone to Hernias
The umbilicus represents a natural point of weakness in the abdominal wall, making it susceptible to hernias. During development, the umbilical cord vessels and ligaments pass through a small opening called the umbilical ring. After birth, this ring is meant to close completely, but imperfect connective tissue closure sometimes occurs.
This incomplete closure leaves a potential gap in the fascia and muscle layers. An umbilical hernia occurs when abdominal contents, usually fat or a loop of intestine, push through this weak spot. The resulting bulge is often noticeable when abdominal pressure increases, such as during crying or straining.