Sebaceous glands

Abstract

Sebaceous glands are found in the skin of all mammals except whales and porpoises (1). One of their functions is to excrete sebum, a mixture of relatively nonpolar lipids, most of which are synthesized de novo by the glands (2). In furred mammals, sebum coats the fur as a hydrophobic protection against overwetting and for heat insulation (3). The composition of sebum is remarkably species specific (2,4,5). In addition, specialized sebaceous-like structures, such as the preputial glands of rodents, are responsible, in many species, primarily for the release of pheromores used for territorial marking and sexual attraction (6,7). In humans, however, these sebaceous gland functions appear to have limited importance. Although sebum is the major ingredient of human skin surface lipids, the latter form no barrier, and sebum has been considered not to have antibacterial or antifungal properties in vivo (8). On the other hand, increased sebum excretion is a major etiological factor involved in the development of acne (9). Hormones control sebaceous gland size and activity, however, the acne patient is not considered to be an androgen mismatch (9). Therefore, Kligman has suggested that the sebaceous gland is a vestigial organ of human development, a “living fossil with a past but no future” (8).