The nasolabial fold was analyzed by anatomic and histologic evaluation
of the tissue planes that create and surround the fold. A fascial-fat
ty layer exists in the superficial subdermal space extending from the
upper lip across the nasolabial fold to the cheek mass. The SMAS is pr
esent in the upper lip as the superficial portion of the orbicularis o
ris muscle. Traction on the SMAS or periosteum lateral to the nasolabi
al fold can deepen the fold, while traction on the fascial-fatty layer
lessens the fold. The fascial-fatty layer and skin of the cheek mass
are suggested as the primary ptotic elements responsible for facial ag
ing.