Which gland is responsible for secreting an oily substance onto hair follicles?

The sebaceous gland is responsible for secreting an oily substance known as sebum onto hair follicles. This oily secretion plays a crucial role in maintaining skin health by providing moisture and reducing the risk of dryness. Sebum also has antibacterial properties, which can help protect the skin from infections. The presence of sebaceous glands is typically associated with hair follicles, as their ducts empty directly into the follicles, allowing the sebum to coat the hair strands and the surrounding skin.

In contrast, sweat glands primarily produce a watery secretion for thermoregulation and do not contribute to the oily characteristic of hair. Mammary glands are specialized for milk production and are not involved in the secretion of oil onto hair. Apocrine glands, while they do contribute to secretion in certain body areas, are not specifically responsible for oil production and instead produce a more protein-rich fluid that contributes to body odor. Understanding the specific functions of these glands highlights the unique role of sebaceous glands in skin and hair health.