Which layer of the epidermis contains flattened, dead cells?

The correct answer is the layer of the epidermis known as the stratum corneum. This outermost layer consists primarily of flattened, dead keratinocytes that have undergone a process called keratinization. During this process, the cells move from the deeper layers of the epidermis towards the surface, gradually losing their nucleus and cytoplasmic contents, which eventually leads to the formation of a tough, protective layer composed mainly of keratin.

The presence of dead cells in the stratum corneum plays a vital role in the skin's barrier function, providing protection against environmental damage, pathogens, and water loss. As these cells continuously shed and are replaced by new cells migrating up from the lower layers, the skin maintains its resilience and adaptability.

Other layers such as the stratum lucidum, stratum spinosum, and stratum granulosum do not primarily consist of dead cells. The stratum lucidum, for example, is found in thick skin and contains a layer of dead keratinocytes that are somewhat translucent but does not reflect the overall structure and function that characterizes the stratum corneum. In contrast, the stratum spinosum houses living keratinocytes that are interconnected via desmosomes and play a