Subkutis

Subkutis, also known as the subcutaneous tissue or hypodermis, is the layer of tissue beneath the dermis. It extends to the deep fascia and surrounds nerves and blood vessels. It consists mainly of adipose (fat) tissue embedded in loose connective tissue, with a rich supply of blood and lymphatic vessels.

Functions: energy storage, insulation against cold, mechanical cushioning, and a mobile, flexible interface that allows skin movement relative to deeper structures. It also houses nerve endings and contributes to thermoregulation through adipose tissue.

Clinical relevance: the subkutis is the typical site for subcutaneous injections (hypodermic injections) because it has relatively few muscle fibers and a rich vascular supply. Absorption rates are slower than intramuscular administration and depend on fat content and perfusion. Conditions affecting subcutaneous tissue include lipodystrophy, edema, panniculitis (inflammation of fat), and infections such as cellulitis.

Assessment and imaging: ultrasound and magnetic resonance imaging can visualize subcutaneous fat layers and related pathology, while clinical examination notes firmness, temperature, and tenderness.