WRINKLES appear in the face because of special subcutaneous muscles attached directly to the skin of the facial region. When these muscles contract, they create, at right angles to their length, a series of furrows, which, because of failing resiliency in the skin, may become permanent. Where no subcutaneous muscles exist, wrinkles do not form. Bodily changes due to age are general, and there is gradual diminution of the underlying skeletal and muscle volume together with general loss of elasticity.
As a result of activity of the facial musculature, the skin of the face is permanently overstretched and, in the absence of elastic properties, hangs in folds and tends to gravitate over the lower parts of the face. This is caused by the inevitable sagging significant of the aging process; stretching of the skin after removal of tumors; folds and wrinkles as aftermaths of weight loss; irradiation and premature atrophy
LEWIS GK. THE SURGICAL TREATMENT OF WRINKLES. AMA Arch Otolaryngol. 1954;60(3):334–341. doi:10.1001/archotol.1954.00720010343007