The microanatomical basis of facial frown lines.

We studied facial frown lines on cadaver skin. These wrinkles persisting after death were kept unmodified during the collecting procedure; some included the underlying bone. Their microanatomical basis lies in the hypodermis where trabeculae of the retinacula cutis are broader and much shorter underneath the wrinkle than in the surrounding skin. These trabeculae contain striated muscle cells. The hypertrophy of the extracellular matrix of the hypodermal septae is probably related to repetitive mechanical stimuli generated by the muscle cells.