Final answer:
The philtrum is the concave surface that is centered and above the top lip, connecting the nose to the upper lip.
Step-by-step explanation:
The philtrum is the concave surface located centered and above your top lip where it dips down. It connects the apex of the nose to the upper lip. This anatomical feature is part of the external nose structures and contributes to our facial appearance.
The philtrum plays a role in human development, as it is formed during the merging of the maxillary and medial nasal processes in the embryo. Failure for these processes to fuse properly can result in a cleft lip, a common developmental defect.