What part of the skin acts as an insulator and cushion for underlying structures?

The subcutaneous layer, also known as the hypodermis, serves as an important insulating and cushioning layer for the body. This layer consists primarily of fat cells, which provide insulation to help regulate body temperature by preventing heat loss. Additionally, the fat within the subcutaneous layer acts as a cushion, protecting underlying structures such as muscles, bones, and organs from impact and trauma.

The epidermis, being the outermost layer of the skin, primarily serves as a protective barrier against environmental factors such as pathogens and UV radiation. While it does play a role in waterproofing, it does not provide insulation or cushioning.

The dermis, lying beneath the epidermis, contains connective tissue, blood vessels, and nerve endings but is more focused on supporting the epidermis and providing elasticity and structural integrity rather than insulation.

The stratum corneum is the outermost layer of the epidermis made up of dead skin cells that provide a protective barrier but does not contribute to insulation or cushioning in a significant way.

Thus, the subcutaneous layer is uniquely suited for the functions of insulation and cushioning, making it the correct choice.