Which layer of skin is primarily composed of 15 to 20 layers of keratinized cells?

The stratum corneum is the outermost layer of the epidermis and is primarily composed of 15 to 20 layers of keratinized cells, also known as corneocytes. These cells are filled with keratin, a protein that provides protection and waterproofing to the skin. This layer serves as a barrier against environmental damage, pathogens, and water loss, which is crucial for maintaining skin health and overall integrity.

The keratinized cells in this layer become increasingly flattened and lose their nuclei as they move upward from the deeper layers of the epidermis, a process known as keratinization. The stratum corneum plays a vital role in the skin's barrier function, and its thickness can vary depending on the area of the body and exposure to friction or irritation. Understanding the structure and function of the stratum corneum is essential for estheticians in providing effective skin care and treatments.