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Sebaceous gland
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The sebaceous gland supplies 90% of the lipids, that is, the fats, found on the surface of the skin.
The way it makes them is unusual, and it is called holocrine secretion. The cell of this gland, the sebocyte, fills with lipids as it matures; once it reaches the center of the gland it undergoes apoptosis, programmed cell death, and breaks apart. What is left of it, mixed with those lipids, is sebum. It is a cell that sacrifices itself: it does not release the product, it becomes it.
From there the sebum has to get out. Because these glands empty into the hair canal, sebum escapes mainly by traveling up the hair shaft to the surface, by capillary action. Once at the top it seals in moisture and keeps the skin from drying out.
In brief
The sebaceous gland supplies 90% of the lipids on the skin's surface.
It makes them by holocrine secretion: the sebocyte, its cell, fills with lipids, undergoes apoptosis and breaks apart; its remains are sebum.
A cell that sacrifices itself: it does not release the product, it becomes it.
Sebum drains into the hair canal and escapes mainly along the shaft to the surface, where it seals in moisture and keeps skin from drying out.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Sebaceous Glands, StatPearlsPublished
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