Which of the following layers is primarily responsible for fat storage?

The subcutaneous layer, also known as the hypodermis, is primarily responsible for fat storage. This layer is located beneath the dermis and contains a significant amount of adipose tissue, which serves several important functions. The fat stored in this layer acts as an energy reserve, insulates the body to help regulate temperature, and provides cushioning to protect underlying structures such as muscles and bones from trauma.

In contrast, the epidermis consists of epithelial tissue and serves primarily as a protective barrier against environmental factors, while the papillary layer and reticular layer, which comprise the dermis, are involved in supporting the skin's structure and providing elasticity and strength, but they do not have a primary role in fat storage. Thus, the subcutaneous layer's composition of adipose tissue clearly distinguishes it as the key site for fat storage in the integumentary system.