The Sebaceous Gland: Anatomy & Physiology
Sebaceous glands are holocrine glands usually associated with the hair follicle, forming the pilosebaceous unit. They are responsible for producing sebum, a lipid-rich secretion that lubricates the skin and hair.
Key Characteristics
| Feature | Description |
|---|---|
| Mechanism | Holocrine secretion: The entire cell disintegrates to release its contents (sebum). |
| Regulation | Primarily controlled by androgens. Activity peaks at puberty. |
| Distribution | High density on the face, scalp, chest, and back. Absent on palms and soles. |
Clinical Significance (The “Acne” Link)
- Acne Vulgaris Pathogenesis: Driven by four factors:
- Increased sebum production (androgen-driven).
- Hyperkeratinization of the follicular duct.
- Colonization by Cutibacterium acnes.
- Inflammatory response.
- Free Sebaceous Glands: Found in areas not associated with hair follicles, such as the eyelids (Meibomian glands), lips (Fordyce spots), and nipples (Montgomery tubercles).
High-Yield Exam Pearl:
- Sebaceous Hyperplasia: Common in elderly patients; appears as yellowish papules with a central umbilication. Often mistaken for basal cell carcinoma.
- Absence: If an exam question asks where sebaceous glands are never found, the answer is always palms and soles.