Final answer:
The primary function of the subcutaneous layer (superficial fascia) is insulation. It provides insulation, acts as a cushion, and stores fats for long-term energy storage.
Step-by-step explanation:
The primary function of the subcutaneous layer (superficial fascia), also known as the hypodermis, is insulation. The hypodermis consists of adipose tissue, which helps to regulate body temperature by providing insulation from the cold. It acts as a cushion for underlying structures and stores fats for long-term energy storage.