When hair dies, the thick fatty layer that contains the sebaceous glands in the scalp shrinks, and has to be thickened up before the follicles can spring back into action.
During the body's early development, stem cells in the skin develop along three different pathways, differentiating into hair follicles, into sebaceous glands for secreting fat to lubricate and waterproof the skin, and into the epidermis itself.
Associated with hair follicles are oil-secreting sebaceous glands as well as tubular glands, which produce an aqueous secretion.
Some, like the chin and anal glands of the rabbit, contain only tubular units; others, like the abdominal gland of the gerbil, are purely sebaceous; still others, like the side glands of shrews, contain batteries of both holocrine and tubular units.
Sebaceous glands are termed holocrine because their secretion involves complete disintegration of their cells, which are constantly replaced.
The outer sides of the labia are covered with pigmented skin, sebaceous (oil-secreting) glands, and after puberty, coarse hair.
An internal sty results from inflammation of a meibomian gland, one of the modified sebaceous glands that lie close to the eyeball along the margin of the eyelids.
The sebaceous glands evenly spaced in rows at the border of the eyelids the meibomian glands are so large that they are easily seen with the naked eye when the eyelids are everted.
Only humans have rich populations of sebaceous glands on the hairless surfaces of the lips; these glands increase in number and size as persons mature.
The glands on the genitalia produce copious amounts of sebaceous matter called smegma.
The inside of the cheeks also has many large sebaceous glands, and occasionally there are glands even on the gums and tongue.
