Call it the belly button, the navel, the umbilicus or as the Greeks called it, the omphalos. This vestige of our fetal lives gets attention for purely cosmetic reasons. Barring rare infections or hernias, or being pierced for jewelry, the navel just sits there, doing nothing.

Structurally speaking, the navel is scar tissue. It forms over the place where the umbilical cord attached us to the placenta. Navels are found not only in humans, but in all other mammals that give birth to live young, namely placental and marsupial mammals. Even the odd monotremes, the only mammals that lay eggs, have a kind of navel, where the yolk sac is attached. This is also true of birds and reptiles.

After birth, the umbilical cord is cut close to the belly, leaving a small stump -- the only mandatory "injury," if it can be called that, experienced by humans. This stump dries up, shrivels and falls off, usually in about a week or two.

We keep our navels because scar tissue is nature's final response to an injury. Scars elsewhere on the body don't disappear, so why should the navel? However, the navel is still a weak spot in the belly because the muscles there are thinner. So hernias can take place, in newborns or adults.

Innie or outie?

Whether in or out, medically speaking, a navel is a navel is a navel. However, people dissatisfied with the shape of their belly button will sometimes resort to the plastic surgeon. Apparently, umbilicoplasty is usually done to turn an "outie" into an "innie." At least, that's how plastic surgeons usually advertise the procedure. Articles about the procedure cite the obsession with thinness: a protruding belly button is unpleasantly reminiscent of a protruding midriff.

More subtle aesthetics come into play, according to a January 2000 study, "In search of the ideal female umbilicus" by Stefan B. Craig and two co-authors. Photos of 147 female navels were taken for the study, published in Plastic and Reconstructive Surgery, the journal of the American Society of Plastic Surgeons.

"The photographs were reviewed by the authors, and each umbilicus was categorized on the basis of size, shape, hooding or protrusion," according to the abstract. "The photographs were then reviewed by a panel and given a score of between 1 and 10 to rate attractiveness."

Result: T- or vertical navels with "superior hooding" rated highest. Smaller navels rated higher than larger navels.

The navel is a means to an end in an even more popular form of plastic surgery: breast enlargement. The implant is squeezed through an incision in the navel and steered toward the breast. The main advantage of "transumbilical breast augmentation," or TUBA, as it is sometimes called, is it doesn't produce scars around the breast. However, it is more difficult to position the implant.

Aside from deliberate tinkering or ogling, the navel doesn't attract any attention. However, pain or inflammation may require treatment. This is usually associated with piercing.

"Friction from clothing with tight-fitting waistbands and subsequent skin maceration may account for the delayed healing and increased infection rates of navel piercings. Careful placement of jewelry and avoidance of rigidly fixed jewelry may minimize these problems," wrote Donna I. Meltzer, M.D., in the Nov. 15, 2005, issue of American Family Physician.

Another complication, Meltzer wrote, is that shallow navel piercings "tend to migrate to the skin surface," This means the points of piercing move closer to the surface, eventually expelling the attached jewelry.

The most radical form of surgery is total removal of the belly button. This is usually not plastic surgery, but a byproduct of more extensive surgery. The Seattle Times published a story by one such man, who had hepatitis and a herniated umbilicus. (tinyurl.com/2Ircj).

Contact staff writer Bradley J. Fikes at (760) 739-6641 or bfikes@nctimes.com.