Which layer of skin is described as consisting of 25 to 30 cells deep of flattened irregular dead keratinised cells?

The layer of skin described as consisting of 25 to 30 cells deep of flattened irregular dead keratinized cells is indeed the stratum corneum. This outermost layer serves as the body's primary barrier against environmental hazards, such as pathogens and physical irritants, and plays a crucial role in preventing transepidermal water loss.

In the stratum corneum, keratinocytes that originated deeper in the epidermis undergo a process called keratinization as they move upward, flattening and filling with keratin, a tough and fibrous protein. As these cells die, they form a protective layer that is crucial for skin integrity and function. The thickness of this layer can vary depending on the area of the body, but its composition of dead, flattened cells is vital for its protective function.

Understanding the unique properties and roles of the stratum corneum helps emphasize its importance in aesthetic treatments, such as exfoliation and hydration, to maintain healthy skin.