The connective tissues of the epimysium and perimysium contain the blood vessels and nerves that supply the muscle fibers. Muscle contraction requires tremendous quantities of energy. An extensive vascular network delivers the necessary oxygen and nutrients and carries away the metabolic wastes generated by active skeletal muscles. The blood vessels and the nerve supply generally enter the muscle together and follow the same branching pattern through the perimysium. Within the endomysium, arterioles supply blood to a capillary network that surrounds each individual muscle fiber.

Skeletal muscles contract only under stimulation from the central nervous system. Axons, or nerve fibers, penetrate the epimysium, branch through the perimysium, and enter the endomysium to innervate individual muscle fibers. Skeletal muscles are often called voluntary muscles, because we have voluntary control over their contractions. Many skeletal muscles may also be controlled at a subconscious level. For example, skeletal muscles involved with breathing, such as the diaphragm, usually work outside our conscious awareness.

Next we will examine the microscopic structure of a typical skeletal muscle fiber and will relate that microstructure to the physiology of the contraction process.