Muscle and Tendon

Abstract

On the whole, skeletal muscles can be regarded as the largest organ of the human body, accounting for approximately 25—35% of the total body weight in women and 40—50% in men (Hollman and Hettiger 1990). They are made up of two components: the muscle fibers, which are long and cylindrical in structure, representing the cellular unit of muscle, and stromal connective tissue. Individual muscle fibers are grouped together in bundles, which are commonly known as fascicles, and several fascicles join together to form an individual muscle (Fig. 3.1a). Thin connective tissue strands — the endomysium — separate the individual muscle fibers; a more substantial connective sheath with small vessels and nerve endings, the perimysium (also referred to as fibroadipose septa), envelops individual fascicles; a thick fibrous layer, the epimysium, surrounds the entire muscle (Fig. 3.1a). Muscle fibers vary in length and cross-sectional diameter depending on the individual muscle. Fascicles may be either coarse, as in the case of large muscles, or very fine, as in the case of small muscles that coordinate precise movement (Erickson 1997).