werner@aecom.UUCP (Craig Werner) (10/02/85)
In this strict sense they do heal. The skin of my navel is
indistinguishable from the skin on the rest of my abdomen. Compare that to
a surgical scar which is almost as old, which is still pink and discolored.
The question is why don't they heal flush. The answer lies in the
underlying anatomy. The rest of the skin of the abdomen lies on top of the
aponeurosis (connective tissue) of the Rectus Abdominus muscle. A fairly
flat muscle it is. Along the midline, there is actually no muscle, just the
tissue of the linea alba (white line), which can be felt if you tighten your
muscles and can be seen on weight-lifters.
There is one exception. Below the navel. The vestiges of the umbilical
circulation interupt the linea alba, and below that they interrupt the
peritoneum (what encloses your guts). Actually, the umbilical veins can be
reopened in the deeper parts and give rise to a Medusa pattern on the
abdomen which is a sign of Liver failure (where the umbilical veins would
empty - its just like traffic backup).
The navel is not just a surface marking. It goes down several layers,
and what is on the surface just does what the rest of the skin does - cling
tightly to its foundation.
--
Craig Werner
!philabs!aecom!werner
"Why is it that half the calories is twice the price?"