hypodermis

The hypodermis is the layer beneath the dermis, also called subcutaneous tissue. It is mostly fat cells held in connective tissue, and it does four jobs: it insulates, it cushions the structures above and below it from pressure, it stores energy, and it anchors the skin to the muscle and bone underneath so the skin does not slide. It carries the larger vessels and nerves on their way to the skin. Its thickness varies by region and by person — the abdomen and hips carry more than the back of the hand — which is why an injection is placed in it where the tissue is thick enough to take the volume and the drug is meant to be absorbed slowly. Because it is fat, it is also where the body's long-term energy reserve sits.