Which layer of the skin is primarily made up of dead skin cells?

The correct answer is the stratum corneum, which is the outermost layer of the epidermis. This layer consists primarily of dead skin cells that have lost their nuclei and are filled with keratin, a protein that provides protection and strength. The stratum corneum plays an essential role in the skin's barrier function, preventing water loss and protecting underlying layers from environmental damage, pathogens, and other harmful substances. The presence of these dead cells also contributes to the natural shedding process of the skin, allowing for renewal and maintaining healthy skin.

The epidermis as a whole does contain living cells, including those in the deeper layers that actively divide and generate new cells, but the stratum corneum specifically is composed of those dead, keratinized cells that protect the body. Other layers of the skin, such as the dermis, are primarily composed of connective tissues, while the hypodermis consists mostly of fat and connective tissue, which support and insulate the body but do not contain significant numbers of dead skin cells.