We just learned about the Vermillion Border no the top of the lip.
Another part of the mouth is the Philtrum.
The philtrum is on the outside of the upper lip, right in the middle, going from the nose to the lip.
For most people this is a little indent or groove.
Some scientists think that this part of the lip used to be used to try and help guide smells up to the nose, back when we used to have to hunt or smell our food more to see if it was ok to eat.
(from: wikipedia - philtrum)
Kid Facts - Blast from the past: Maxillary First Premolar
