Which layer of the skin is often referred to as the 'horny layer'?

The layer of the skin commonly referred to as the "horny layer" is the stratum corneum. This is the outermost layer of the epidermis and is primarily composed of dead keratinized skin cells, which have become flattened and hardened. The keratin in this layer provides a protective barrier against environmental factors, such as pathogens and moisture loss. The thickness of the stratum corneum can vary depending on the location on the body, contributing to the skin's ability to act as a protective shield.

This term "horny layer" is derived from the word "corneous," which reflects the tough, protective nature of the cells in this part of the skin. Its primary role is to prevent transepidermal water loss and protect underlying tissues from mechanical injury, pathogens, and harmful substances. Understanding this layer's function is crucial for estheticians as they work with skin care and treatments, emphasizing the importance of maintaining its health and integrity.