Comparative Anatomy and Facial Aging in the Animal Kingdom

Since the beginning of modern plastic surgery discipline, facial aging has been a significant interest to plastic surgeons. One turning point for aesthetic surgery was the recognition that facial aging is more than skin deep and that any attempts at facial rejuvenation must address the subcutaneous connective tissue (i.e., fat, fascia, and muscle) [1-3]. Having been exposed to Tord Skoog’s presentation and the 1969 publication, two surgeons from the Tessier group published the now-famous cadaveric study on the superficial fascia of the face, which was popularized under the term superficial muscular and aponeurotic system [4]. Subsequent to this, plastic surgeons began to abandon simple rhytidectomy procedures but instead developed a wide variety of techniques by which the deeper connective tissue is mobilized to restore a more youthful contour to the face. Outside of the plastic surgery literature, a different discipline has been interested in the convergence and divergence in the anatomy and functions of the facial muscle. While the nature of facial soft tissues interested plastic surgeons because of potential applications in aesthetic and reconstructive operations, biologists and comparative anatomists were more interested in what similarities and differences could be observed across facial structures of various animals because these similarities and differences were helpful in understanding the evolution of muscles innervated by the seventh cranial nerve (CN-VII). In this editorial, we would like to review the non-plastic surgery literature on the evolution of facial muscle (CN-VII muscles) and question again the nature of facial aging. ORIGIN OF FACIAL MUSCLES