What is the primary component of the skin's waterproof barrier?

The primary component of the skin's waterproof barrier is lipids. These substances are crucial for maintaining hydration and preventing excessive water loss from the body. In the skin, particularly in the stratum corneum (the outermost layer of the epidermis), lipids form a lipid matrix that contributes to a barrier function. This lipid matrix includes ceramides, fatty acids, and cholesterol, which work together to create a semi-permeable membrane that keeps moisture in while keeping harmful substances out.

Keratin, though important for the structural integrity and protective qualities of the skin, is primarily a protein found in hair, nails, and the outer layer of skin, contributing to its strength rather than its waterproof nature. Collagen provides structural support and elasticity to the skin but is not involved in the barrier function. Elastin contributes to the skin's elasticity but also does not play a role in creating the waterproof barrier. Thus, lipids are the essential component that maintains skin hydration and overall integrity.