Ultrastructure of the intramuscular connective tissue in bovine skeletal muscle. A demonstration using the cell-maceration/scanning electron microscope method.

The three-dimensional arrangement of intramuscular connective tissues in bovine semitendinosus muscle was investigated using the cell-maceration method for scanning electron microscopy, by which cellular elements were eliminated and collagen fibrils and fibers were exposed. The 60-100 microns diameter honeycomb structures of the endomysium housing individual muscle fibers were clearly observed. The sheath of endomysium was membranous and consisted of tightly arranged collagen fibrils 30-70 nm in diameter. The perimysium was composed of several layers of 100-200 microns-thick sheets surrounding the sheaths of the endomysium. The sheets of the perimysium were wavy and consisted of collagen fibers made up of tightly bundled fibrils. The epimysium was composed of two distinct layers of thick sheets. The inner layer consisted of thousands of collagen fibers lying in an extremely regular wavy pattern parallel to the axis of the muscle fiber. The outer layer of epimysium was composed of several wavy sheets of collagen fibers which ran transversely to the axis of the muscle fiber. In a region of the epimysium, there was a thick wall of about 1 mm thickness, where fiber bundles of 200-300 microns in diameter ran longitudinally parallel to the axis of muscle fiber.