ABSTRACT
The sebaceous glands exude lipids by disintegration of entire cells, a process
known as holocrine secretion. The life span of a sebocyte from cell division to
holocrine secretion is approximately 21 to 25 days (1). Because of the constant
state of renewal and secretion of the sebaceous gland, individual cells within the
same gland are engaged in different metabolic activities dependent on their
differentiation state (2). The stages of this process are evident in the histology of
the gland (3). The outermost cells, basal cell layer membrane, are small,
nucleated, and devoid of lipid droplets. This layer contains the dividing cells that
replenish the gland as cells are lost in the process of lipid excretion. As cells are
displaced into the center of the gland, they begin to produce lipid, which
accumulates in droplets. Eventually, the cells become greatly distended with
lipid droplets with the nuclei and other subcellular structures disappearing. As
the cells approach the sebaceous duct, they disintegrate and release their con-
tents. Only neutral lipids reach the skin surface. Proteins, nucleic acids, and the
membrane phospholipids are digested and most likely recycled during the dis-
integration of the cells.
