What is the thickest layer of the epidermis?

The thickest layer of the epidermis is the stratum corneum. This outermost layer consists of dead, flattened keratinocytes that are continuously shed and replaced. It plays a critical role in protecting the underlying layers of the skin, preventing water loss, and providing a barrier against environmental hazards such as pathogens and chemicals. The thickness of the stratum corneum can vary significantly depending on the location on the body, being thicker in areas subject to abrasion, such as the palms of the hands and soles of the feet.

In contrast, the stratum basale is the deepest layer of the epidermis and is primarily responsible for producing new skin cells. The stratum spinosum contains several layers of keratinocytes and provides strength and flexibility to the skin, while the stratum granulosum is where keratinocytes begin to undergo a process of keratinization, ultimately contributing to the formation of the stratum corneum above it. Therefore, when considering thickness, the stratum corneum is distinguished as the most substantial layer.