Which structural characteristic defines the stratum granulosum layer?

The stratum granulosum is a specific layer of the epidermis that is primarily characterized by the presence of granular cells undergoing a process associated with cell death. In this layer, keratinocytes begin to lose their nuclei and organelles while accumulating keratohyalin granules, which play a significant role in the keratinization process. This granular appearance is indicative of the transition stage where these cells are moving towards becoming more protective keratinized cells that will form part of the outermost skin barrier.

While keratinocytes do exist in this layer, their defining characteristic here is not merely their presence but rather their metabolic activity and structural changes, which align with the accumulation of granules and the eventual onset of cell death. This process contributes significantly to the formation of the skin’s protective outer layer.

Mitotic activity is more characteristic of the deeper layers of the epidermis, such as the stratum basale and stratum spinosum, where new skin cells are generated. Similarly, a thickened cell layer would not pertain specifically to the stratum granulosum but could describe other layers where cell proliferation is more pronounced.