Fascias

Fascias are sheets or bands of connective tissue that enclose, separate, and support muscles, organs, vessels, and nerves. They form a continuous three‑dimensional network that extends from the skin to internal cavities. The fascial system contributes to mechanical integrity, transmits muscular forces, stabilizes compartments, and contains a rich supply of sensory receptors that inform position and tension.

Superficial fascia lies just below the skin and often contains fat, loose connective tissue, blood vessels, and cutaneous nerves. Deep fascia consists of dense irregular connective tissue that envelopes individual muscles and forms intermuscular compartments and retinacula, as well as investing fascia that surrounds neurovascular bundles. Visceral (or subserous) fascia lines body cavities and surrounds internal organs, while subserous fascia lies between serous membranes and the structures they cover.

Fascia is primarily composed of collagen fibers with varying amounts of elastin and extracellular matrix, and it is well supplied with nerves. The density and orientation of collagen fibers determine its mechanical properties, which can adapt to movement and loading. The tissue is highly innervated, with mechanoreceptors contributing to proprioception and reflex responses.

Clinically, fascia plays a role in the organization of muscle compartments and in surgical approaches. Pathological changes such as scarring, thickening, or adhesions can alter movement or cause pain in some conditions. Techniques addressing fascia, including physical therapy and manual therapies, aim to restore glide and flexibility, though evidence for effectiveness varies by condition.

Examples include the fascia lata of the thigh, the thoracolumbar fascia of the back, and the plantar fascia of the foot.