Which skin layer serves as the primary barrier between the body and the environment?

The primary barrier between the body and the environment is the stratum corneum, which is the outermost layer of the epidermis. This layer is composed of dead, flattened skin cells that are rich in keratin, a protein that provides toughness and waterproofing. As the first line of defense, the stratum corneum plays a crucial role in protecting the underlying layers of skin and the body from environmental hazards, such as pathogens, chemicals, and physical abrasions. It also helps to prevent water loss, maintaining hydration within the skin.

In contrast, the stratum granulosum is located beneath the stratum corneum and is involved in the process of keratinization, where skin cells begin to die and form a more protective barrier. The stratum germinativum, also known as the basal layer, is responsible for generating new skin cells. Lastly, the stratum lucidum is found only in certain areas of thick skin, such as the palms and soles, and acts as an additional layer of protection, but it doesn't serve the primary barrier function that the stratum corneum does.