The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. The epidermis is composed of multiple layers of flattened cells that overlie a base layer (stratum basale) composed of columnar cells arranged perpendicularly.

Answer this question based on the passage: which is the uppermost layer of the skin? Okie... think carefully first, then make a decision:
To answer the above question, the relevant sentence is: The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and hypodermis. So, the answer is The epidermis.