ABSTRACT
Sebaceous Glands 307
Anatomy 307
Distribution 308
Sebum Secretion 308
Methods for Measurement 308
Hormonal Control 309
Variation with Age and Gender 310
Sebum Composition 310
Human 310
Lipid Class Composition 310
Fatty Chains 311
Other Species 313
Sebum in Health 313
Sebum in Disease-Acne 314
References 315
SEBACEOUS GLANDS
Anatomy
Sebaceous glands are multilobular holocrine glands generally associated with
hair follicles (1). The basal sebocytes sit on a basal membrane at the outer
limits of the lobes, and as cells move from the basal layer toward the lumen of the
gland they synthesize lipids, which accumulate as intracellular lipid droplets. As
they synthesize lipid, the cells become larger, and the nucleus and other internal
organelles are degraded. Ultimately, the entire mass of the cell is converted into a
viscous liquid phase lipid mixture. In most pilosebaceous units, sebum passes
from the sebaceous gland into the hair follicle via the short sebaceous duct and
outward onto the skin surface through the follicle. Generally, the hair follicle
is large compared with the associated sebaceous gland; however, large sebaceous
glands are associated with vellous hairs. These units are called sebaceous follicles
and predominate on the forehead and cheeks.
