épimysium

The epimysium is the outermost layer of connective tissue that surrounds a skeletal muscle. It lies beneath the surrounding deep fascia and sits external to the perimysium, which encloses individual fascicles within the muscle. At the muscle’s ends, the epimysium blends with the connective tissue of tendons or aponeuroses that attach the muscle to bone or to another structure.

The epimysium is primarily composed of dense irregular connective tissue, rich in collagen type I fibers, with fibroblasts and occasional elastin fibers. This composition provides strength and resilience while allowing multidirectional stretch. The epimysium houses blood vessels and nerves that enter the muscle, and it forms a conduit for these structures to reach the inner fascicles.

Functionally, the epimysium helps transmit the force generated by muscle fibers to the tendon and eventually to the bone, contributing to the overall mechanical integrity of the muscle. It also helps distribute stress across the muscle, protects internal components, and participates in proprioceptive sensing through its innervation and mechanoreceptors. The epimysium is continuous with the fascia of the surrounding tissues and with the tendon, facilitating integrated movement and force transfer within the musculoskeletal system.

Clinical notes can include considerations in surgical incisions or injuries that involve the outer muscle layers, where disruption of the epimysium may affect healing and force transmission.