Final answer:
The stratum spinosum plays a crucial role in skin protection, where the daughter cells from the stem cells differentiate into keratinocytes that synthesize keratin and a water-repelling glycolipid and are joined together by desmosomes.
Step-by-step explanation:
In the stratum spinosum, the daughter cells from stem cells transform into keratinocytes, which are essential for the formation of the outer layer of the skin. This is a critical process where these keratinocytes begin synthesizing keratin, a fibrous protein that gives the skin its durability and protective capabilities. Additionally, these cells start secreting a water-repelling glycolipid, essential for the skin's barrier function, preventing excessive water loss and making the skin water-resistant.
The stratum spinosum is characterized by its spiny appearance, which results from the desmosomes—specialized structures that interlock and strengthen the bond between the cells. As the keratinocytes mature, they are pushed up toward the stratum granulosum, undergoing further changes, and getting closer to their final stage as part of the skin's protective barrier. The presence of Langerhans cells among keratinocytes indicates the immunological function of the skin. These cells act as macrophages, engulfing pathogens and presenting antigens to the immune system, thereby contributing to the skin's defense mechanisms.