The primary function of sebaceous glands is to produce what substance?

The primary function of sebaceous glands is to produce sebum. Sebum is an oily substance that helps to lubricate and protect the skin and hair. It plays a crucial role in maintaining the skin's barrier function, preventing dehydration, and providing a certain level of antimicrobial protection. By producing sebum, sebaceous glands contribute to the overall health and appearance of the skin, helping to keep it moisturized and supple.

In contrast, the other substances listed serve different roles in the body. Melanin is a pigment responsible for skin color and protection against UV radiation, while keratin is a structural protein that provides strength and resilience to skin, hair, and nails. Collagen is a protein that offers structural support to skin and other tissues, contributing to its firmness and elasticity. Understanding the unique functions of these substances emphasizes the specialized role of sebum in skin health and maintenance.