Which layer of the skin is primarily involved in insulation and fat storage?

The layer of skin primarily involved in insulation and fat storage is the hypodermis, also known as the subcutaneous layer. This layer contains a significant amount of adipose tissue, which serves as an insulator to help maintain body temperature and provides a cushioning effect to protect underlying structures. The presence of fatty tissue in the hypodermis also functions as an energy reserve, storing fat that the body can draw upon when needed.

In contrast, the epidermis is the outermost layer of skin that primarily serves as a protective barrier against environmental factors like pathogens and UV radiation, but it does not significantly contribute to insulation or fat storage. The dermis, located beneath the epidermis, provides structural support and elasticity to the skin, containing connective tissues, hair follicles, and glands, but it is not the main site for fat storage. The stratum corneum is the outermost layer of the epidermis, composed of dead skin cells that create a barrier but also lacks fat storage capabilities. Thus, the hypodermis is the correct choice for its role in insulation and fat storage.