Accessory Structures of the Skin: Sebaceous Glands

The sebaceous or oil glands are present over the entire body, except the palms and soles.

They are located in the dermis and contain sebocytes - specialized cells that produce an oily secretion called sebum.

The sebaceous glands are a type of holocrine glands because the cells rupture to release the sebum to the epidermis through the associated hair follicles. In the case of sebaceous follicles - the large sebaceous glands not associated with hair follicles, sebum is released directly via ducts.

Sebum is a mixture of triglycerides, cholesterol, fatty acids, squalene, and wax esters, giving it an oily texture.

It lubricates the skin and hair and retains moisture by reducing water loss. In addition to the lipid molecules, sebum contains some antimicrobial peptides that inhibit microbial growth on the skin.

Sebum overproduction due to stress or hormonal imbalance can block the gland's opening, causing acne with varying severity.

Often, inflammation around the overactive sebaceous glands can cause seborrheic dermatitis — a condition with red, itchy, and scaly skin.