What substance is secreted by sebaceous glands?

Sebaceous glands are specialized glands in the skin that are responsible for producing an oily substance known as sebum. This sebum is composed primarily of lipids, including triglycerides, wax esters, and squalene. The primary function of sebum is to lubricate and waterproof the skin and hair, helping to prevent dryness and maintain skin integrity. By secreting oils, sebaceous glands play a crucial role in protecting the skin from environmental damage and reducing water loss.

The other substances listed are produced by different types of glands or cells in the body. Sweat, for example, is secreted by sweat glands and serves to regulate body temperature and eliminate waste. Wax is typically associated with the ceruminous glands found in the ear, which produce earwax to protect the ear canal. Melanin is a pigment produced by melanocytes in the skin that is responsible for skin coloration and protection from UV radiation, rather than being secreted by sebaceous glands.