Endomysium

The endomysium is a thin layer of loose connective tissue that surrounds each individual skeletal muscle fibre (muscle cell). It lies external to the muscle fibre’s basal lamina and sarcolemma (cell membrane), forming the innermost of the three connective tissue sheaths of skeletal muscle.

The endomysium consists mainly of reticular fibres (type III collagen), a rich capillary network, and fine nerve fibres, providing structural support and the microenvironment for metabolic exchange between muscle fibres and the circulation.

Relations

• To the sarcolemma: The sarcolemma is the plasma membrane of a muscle fibre, surrounded externally by the basal lamina. The endomysium lies immediately outside this basal lamina, anchoring each fibre to the surrounding connective tissue network.

• To the perimysium: Groups of muscle fibres are bundled into fascicles, each enclosed by the perimysium, a thicker connective tissue layer. The endomysium of adjacent fibres merges with the perimysium, ensuring mechanical continuity for force transmission across the muscle.