Which of the following best describes the process of keratinization?

Keratinization is the process where skin cells gradually undergo a transformation, leading to their hardening and drying as they migrate to the surface of the skin. This process is essential for the formation of a protective barrier that prevents water loss and shields the underlying tissues from external environmental factors, such as pathogens and physical damage.

During keratinization, cells known as keratinocytes in the epidermis (the outer layer of skin) produce keratin, a protein that is key to this protective barrier. As these cells move upwards through the layers of the skin, they lose moisture, become flattened, and accumulate keratin. Eventually, they die and form a tough, protective layer of dead cells that constitutes the stratum corneum, the outermost layer of the epidermis.

The other options do not accurately describe keratinization: the formation of sweat relates to sweat glands and thermoregulation, growth of new skin cells pertains to the process of cell turnover and proliferation, while destruction of skin tissues refers to trauma or pathological conditions affecting skin integrity. Thus, the correct description of keratinization is the hardening and drying of skin cells.