Final answer:
The hypodermis is the innermost layer of skin that connects the skin to the underlying tissue, stores fat, and provides insulation and cushioning. It is composed of loose connective tissue and adipose tissue, and it also plays a role in skin hydration and elasticity.
Step-by-step explanation:
The hypodermis, also known as the subcutaneous layer or superficial fascia, is the innermost layer of skin, lying directly below the dermis. It is responsible for connecting the skin to the underlying fascia of the bones and muscles. While not a part of the skin, the hypodermis plays a critical role in the body's function.
This layer is composed of well-vascularized, loose, areolar connective tissue and adipose tissue, which serves as a repository for fat storage and provides insulation and cushioning for the body, known as the integument. The hypodermis contains about 50 percent of the body's fat and is integral in attaching the dermis to the bones and muscles, as well as supplying nerves and blood vessels to the dermis.
Collagen fibers extend from both the dermis into the hypodermis, adding strength and hydration to the skin. This layer is also involved in the efficacy of treatments such as collagen injections and Retin-A creams, which help restore skin elasticity and turgor.