Which layer of the skin contains fatty tissue for insulation?

The layer of the skin that contains fatty tissue for insulation is the hypodermis. This layer, also known as the subcutaneous layer, is situated beneath the dermis and is composed largely of adipose tissue, which serves critical functions including the insulation of the body and the storage of energy.

Adipose tissue in the hypodermis acts as a cushion, protecting underlying structures such as muscles and bones from trauma. Additionally, it helps regulate body temperature by preventing excessive heat loss. The presence of this fatty layer distinguishes the hypodermis from the epidermis and dermis. The epidermis is primarily composed of epithelial cells and does not contain any significant amounts of fatty tissue. The dermis, while it does house some connective tissue and blood vessels, does not have the same insulating properties as the hypodermis, as it is primarily involved in supporting the epidermis and providing nourishment through vascular supply.

The stratum lucidum is a specific layer of the epidermis found only in certain areas (like the palms of the hands and soles of the feet) and does not contain any fatty tissue. Thus, the hypodermis is correctly identified as the layer responsible for insulation through its fatty tissue.