To discuss the formation mechanism of the aging characteristics of the labiomandibular fold in the lower face, through anatomical and histological study of the labiomandibular fold area.

①The methylene blue dye was injected into the jowl fat compartment and the labiomandibular fat compartment which were located in one side of the face of adult fresh cadaveric heads(5 male, 3 female), the labiomandibular fold area was the uncolored region which between the two colored fat compartments. ②Combining with the observation by eyes, symmetrical region of theobjective ly marked labiomandibular fold on the other side of the face in the same head was selected to dissect with microsurgery technique under microscope. The locations, characteristics and adjacent relationships of the anatomical structures of the labiomandibular fold were observed carefully. During the experiment, some related tissues were measured by vernier caliper and recorded by the text and image. ③The symmetrical region of the marked labiomandibular fold with the methylene blue dye (step①) was cut, dehydrated, imbedded in paraffin and serially sliced in cross-section with the thickness of 10 μm. After that, the sections were used to perform HE stain and Masson stain.

The labiomandibular fold is the area of the face which located in the surface of the depressor anguli oris muscle and extends from the mouth corner to the mandibular border. The superior boundary of the labiomandibular fold is formed by the cutaneous insertion of the depressor anguli oris muscle around the mouth corner. The inferior boundary is the mandibular ligament. The lateral and medial area of the labiomandibular fold are the jowl fat compartment and the labiomandibular fat compartment respectively. However, the adipose tissue of the jowl fat compartment is bigger, thicker, looser and lighter in color. Theresult of the histologic evaluation are consistent with the findings of the gross anatomy.

According to the characteristics of the labiomandibular fold, there are many aspects of reasons for the emergence of the labiomandibular fold, such as the relaxation of the facial retaining ligaments associated with the labiomandibular fold and the descensus of the lateral soft tissue of the labiomandibular fold with age. In addition, the differences in structure and morphology between the medial and lateral fat compartments of the labiomandibular fold also play a vital role.

Labiomandibular fold; Facial retaining ligaments; Facial aging; Microdissection