A fascia (/?f???/, /?f??i?/; plural fasciae /?f???.i/; adjective or fascial; from Latin: "band") is connective tissue fibers, primarily collagen, that form sheets or bands beneath the skin to attach, stabilize, enclose, and separate muscles and other internal organs. Fasciae are classified according to their distinct layers, their functions and their anatomical location: superficial fascia, deep (or muscle) fascia, and visceral (or parietal) fascia.
Like ligaments, aponeuroses, and tendons, fasciae are dense regular connective tissues, containing closely packed bundles of collagen fibers oriented in a wavy pattern parallel to the direction of pull. Fasciae are consequently flexible structures able to resist great unidirectional tension forces until the wavy pattern of fibers has been straightened out by the pulling force. These collagen fibers are produced by the fibroblasts located within the fascia.
Fasciae are similar to ligaments and tendons as they have collagen as their major component. They differ in their location and function: ligaments join one bone to another bone, tendons join muscle to bone and fasciae surround muscles or other structures.