hypodermis

The hypodermis, also called the subcutaneous tissue, is the layer of tissue beneath the dermis. It is not considered part of the skin proper. The hypodermis consists mainly of loose connective tissue and adipose tissue, with an extensive network of blood vessels, nerves, and lymphatics. It binds the skin to underlying structures such as muscles and fascia and allows limited movement of the skin over deeper tissues.

Functions include insulation, energy storage in the form of fat, and cushioning or shock absorption for underlying tissues and organs. The adipose component also serves as a metabolic reservoir and plays a role in thermoregulation and hormonal signaling.

The structure and thickness of the hypodermis vary across the body, among individuals, and with age and sex. The adipose tissue is organized into superficial and deeper layers in some regions and is sometimes referred to as panniculus adiposus. It contains blood vessels, nerves, and immune cells.

Clinically, the hypodermis is the common site for subcutaneous injections, including insulin, and for procedures such as liposuction. Disorders affecting this layer include lipomas (benign fatty tumors), lipodystrophy (abnormal fat distribution), and panniculitis (inflammation of the subcutaneous fat).