Development and Validation of a Multiparametric Semiquantitative Scoring System for the Histopathological Assessment of Ischaemia Severity in Skeletal Muscle

Figure 1

Structure of skeletal muscle. The epimysium is a tough connective tissue that surrounds bundles of long muscle fibers called muscle fascicles. These fascicles are surrounded by their own protective layer called the perimysium. The fascicles contain a bundle of muscle fibres that are wrapped a thin layer of connective tissue called endomysium. The nuclei of myofibers are oval-shaped and are located at the periphery of the cell. Each myofiber contain multiple myofibrils, which are composed of numerous sarcomeres, the smallest functional unit of a skeletal muscle fiber, and have light and dark regions that give the cell its striated appearance. Myofibers also have numerous mitochondria for energy generation. The deep neurovascular bundle is a structure of protective connective tissue that surrounds nerves, artery, and veins, so they can travel in tandem through the body. Primary vessels and nerves travel longitudinally along the axis of the muscle and give rise to secondary branches that penetrate the different layers of connective tissue at right or oblique angels to the primary vessels and give rise to numerous terminal branches and capillaries. At the endomysium, several capillaries surround each individual muscle fiber, which travel parallel to the muscle fiber axis. Myofibers are also supplied with the axon branch of somatic motor neurons which signal fiber contraction after receiving an impulse.