Page 45 - 84 human physiolofy part-1

The Integumentary System

Sebaceous Glands

The sebaceous glands are glands found in the skin
of mammals. They secrete an oily substance called
sebum (Latin, meaning fat or tallow) that is made of
fat (lipids) and the debris of dead fat-producing cells.
These glands exist in humans throughout the skin
except in the palms of the hands and soles of the feet.
Sebum acts to protect and waterproof hair and skin,
and keep them from becoming dry, brittle, and
cracked. It can also inhibit the growth of
microorganisms on skin.

Sebaceous glands can usually be found in hair-
covered areas where they are connected to hair
follicles to deposit sebum on the hairs, and bring it to Schematic view of a hair follicle with sebaceous gland.
the skin surface along the hair shaft. The structure
consisting of hair, hair follicle and sebaceous gland is also known as pilosebaceous unit. Sebaceous
glands are also found in non haired areas of lips, eyelids, penis, labia minora and nipples; here the
sebum reaches the surface through ducts. In the glands, sebum is produced within specialized cells and
is released as these cells burst; sebaceous glands are thus classified as holocrine glands.

Sebum is odorless, but its bacterial breakdown can produce odors. Sebum is the cause of some
people experiencing "oily" hair if it is not washed for several days. Earwax is partly sebum, as is
mucopurulent discharge, the dry substance accumulating in the corners of the eye after sleeping.

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