Epimisio

Epimisio, or epimysium, is the outer fibrous connective tissue sheath that surrounds a skeletal muscle as a whole. It encloses the entire muscle belly and separates it from adjacent muscles, while connecting with surrounding fascia and the tendon at the muscle’s insertion.

The epimysium is composed primarily of dense irregular connective tissue rich in collagen fibers. It contains blood vessels and nerves that supply the muscle and is typically continuous with the deep fascia of the surrounding region. At the muscle-tendon junction, the epimysium blends into the tendon fibers, helping to transmit force from muscle to bone.

Functionally, the epimysium provides mechanical protection and structural integrity for the muscle. It helps distribute the forces generated by muscle contraction, shapes and confines the muscle, and supports the passage of blood vessels and nerves. By organizing muscle into a cohesive unit, it also contributes to the muscle’s elasticity and response to stretch.

In the hierarchical organization of skeletal muscle, the endomysium surrounds individual muscle fibers, the perimysium surrounds fascicles of fibers, and the epimysium surrounds the entire muscle. Together, these layers form the muscle’s connective tissue system and establish continuity with the surrounding fascia and tendons.

Clinical relevance includes injuries and strains that can involve disruption or excessive stretching of the epimysium. Surgical and rehabilitation considerations may address epimysial integrity to preserve or restore efficient force transmission and muscle function.