umbilicus

The umbilicus, commonly called the navel or belly button, is the scar on the abdomen that marks the site where the umbilical cord attached to the fetus. In humans it is typically near the center of the abdomen, roughly at the level of the T10 dermatome and approximately halfway between the xiphoid process and the pubic symphysis.

Anatomy and development: The umbilicus forms where the ventral body wall closes around the umbilical cord during embryonic development. In fetal life the cord contains two arteries and one vein that circulate blood between fetus and placenta; after birth the cord is cut and the vessels regress to fibrous remnants. The umbilical region is linked to several ligaments: the fibrous remnant of the umbilical vein becomes the ligamentum teres hepatis, the umbilical arteries become the medial umbilical ligaments, and the urachus forms the median umbilical ligament between the bladder and the umbilicus.

Appearance and variations: Most individuals have an innie or a shallow outie, with depth and prominence influenced by body habitus, scarring, and age. Variations in shape are common, and changes can occur with weight gain, pregnancy, or surgical procedures.

Clinical significance: The umbilicus serves as an important clinical landmark. Umbilical hernias occur when abdominal contents protrude through the umbilical ring, especially in infants or in adults with increased intraabdominal pressure. The region can also be involved in infections, piercings, or cosmetic concerns. Related congenital conditions include omphalocele, where腹 contents herniate into the umbilical cord, and gastroschisis, which are defects around the umbilicus.