Sebum is secreted from sebaceous glands located within the dermis of the skin.
Sebaceous Glands: The Source of Sebum
Sebaceous glands are small, microscopic exocrine glands in the skin that secrete an oily or waxy substance called sebum. These glands are typically associated with hair follicles, meaning sebum is usually released into the follicle and then onto the skin's surface. However, some sebaceous glands, like those on the eyelids (Meibomian glands), lips (Fordyce spots), nipples, and genitalia, are not associated with hair follicles and secrete sebum directly onto the skin's surface.
Composition and Function of Sebum
Sebum is a complex mixture of lipids, including triglycerides, wax esters, squalene, and cholesterol. Its primary function is to:
- Lubricate the skin and hair: This prevents dryness and cracking.
- Provide a waterproof barrier: Sebum helps to repel water and protect the skin from external elements.
- Inhibit the growth of bacteria and fungi: Certain components of sebum have antimicrobial properties.
Factors Affecting Sebum Production
Sebum production can vary depending on several factors, including:
- Hormonal levels: Androgens (male hormones) stimulate sebum production, which explains why sebum production increases during puberty.
- Genetics: Some individuals are genetically predisposed to produce more or less sebum.
- Age: Sebum production typically decreases with age.
- Environment: Exposure to certain environmental factors, such as humidity, can affect sebum production.
- Medications: Certain medications can also influence sebum production.
Associated Conditions
Disruptions in sebum production can lead to various skin conditions, such as:
- Acne: Excessive sebum production can clog pores and contribute to the formation of acne.
- Seborrheic dermatitis: This common skin condition causes scaly, inflamed patches on the scalp, face, and other areas rich in sebaceous glands.
- Dry skin: Insufficient sebum production can lead to dry, itchy, and flaky skin.
In conclusion, sebum, the oily substance that lubricates and protects our skin, is secreted from the sebaceous glands found within the dermis. These glands are usually associated with hair follicles, but some are found independently on areas like the eyelids and lips.
