What is the hypodermis primarily composed of?

The hypodermis, also known as the subcutaneous layer, is primarily composed of connective tissue and fat. This layer serves several essential functions in the integumentary system. The connective tissue provides structural support and anchors the skin to underlying structures such as muscles and bones. The fat within the hypodermis plays a vital role in energy storage, insulation, and cushioning for the body. This layer helps to insulate the body, regulating temperature by minimizing heat loss and protecting underlying organs and structures from trauma.

In contrast, the other options highlight components that do not accurately describe the primary composition of the hypodermis. Muscle tissue, while present in deeper layers of the body, is not a significant component of this layer. A layer of skin cells refers more to the epidermis, which is the outermost layer of skin, rather than the hypodermis. Elastic fibers and blood vessels are indeed present in the hypodermis, but they do not represent the primary composition, which is fundamentally characterized by the presence of connective tissue and fat.