The umbilicus, commonly known as the belly button, represents a central landmark on the anterior abdominal wall. It is the remnant of the umbilical cord, which supplied nutrients during fetal development. Anatomists often use its location to define the umbilical region, a complex area housing a collection of organs and supportive structures within the abdominal cavity. Understanding the anatomy behind this superficial scar requires looking past the skin and muscle layers to the organs and intricate network of vessels they contain.
The Primary Digestive Occupants
The most direct answer to what lies immediately behind the navel is a significant portion of the small intestine. This organ is a long, coiled tube, approximately 22 feet in length in adults, that floats freely within the abdominal cavity. Loops of the jejunum and ileum, the middle and final sections, tend to occupy the central umbilical region. They are suspended there by the mesentery, a fold of tissue.
The jejunum and ileum are the primary sites where digestion is completed and nutrients are absorbed into the bloodstream. The jejunum mainly occupies the central and upper left abdomen, while the ileum is concentrated in the central and lower right areas. Their mobile loops frequently intermingle behind the navel. These organs are covered by the peritoneum, a thin membrane, and the omentum, a protective apron of fat, which helps to cushion and insulate the internal structures.
While the small intestine dominates the immediate central space, other digestive components are considered part of the broader umbilical region. A section of the large intestine, known as the transverse colon, crosses the abdomen horizontally and may dip down into this area. The stomach, pancreas, and portions of the duodenum are situated slightly higher in the adjacent epigastric region, but their boundaries can overlap with the umbilical zone.
The Major Vascular and Connective Network
Deep to the digestive organs in the umbilical region lies a crucial support system of blood vessels and connective tissues. The body’s largest arteries and veins, the abdominal aorta and the inferior vena cava, run along the posterior wall of the abdomen, positioned behind the intestines. These massive vessels supply and drain the lower half of the body.
Branching off the aorta are the mesenteric arteries and veins, which form an expansive network that supplies and drains the small and large intestines. These vessels run within the folds of the mesentery, connecting the central digestive organs to the main circulatory system. Small arteries that supply the abdominal wall near the navel, such as the deep inferior epigastric arteries, also contribute to local circulation.
The navel is a nexus of former fetal structures that persist as connective tissue in the adult. Remnants of the umbilical arteries become the medial umbilical ligaments. The median umbilical ligament is the remnant of the urachus, which connected the fetal bladder to the umbilical cord. These fibrous cords anchor the deep layers of the abdominal wall, attaching internal structures to the surrounding muscle and fascia.
Understanding Umbilical Hernias
The navel area is a natural point of weakness in the abdominal wall, making it a common site for an umbilical hernia. This weakness exists because the umbilical ring, an opening that allowed the umbilical cord to pass through during fetal development, is the last area of the abdominal muscle to close. A hernia occurs when a portion of internal tissue, most commonly a loop of small intestine or abdominal fat (omentum), pushes through this weak spot.
Umbilical hernias are frequently observed in infants, known as congenital hernias, and often close spontaneously by the time a child reaches five years of age. Acquired hernias in adults are less common and result from chronic conditions that increase intra-abdominal pressure. Factors that contribute to the development of an adult hernia include:
- Multiple pregnancies
- Obesity
- Excessive fluid in the abdomen (ascites)
- Persistent coughing
The most common symptom is a visible bulge or swelling near the navel, which may become more prominent when straining, coughing, or crying. While often painless in children, hernias in adults can cause discomfort. Prompt medical evaluation is necessary if the bulge becomes tender, discolored, or is accompanied by vomiting. These severe symptoms may indicate a strangulated hernia, where the blood supply to the trapped tissue is cut off, requiring urgent medical intervention.