Chapter 2 - Functional Morphology of the Striated Muscle

Abstract

The anatomical elements of the muscular tissue are the muscle fibers which consist of tightly packed cytoplasmic filaments in a highly ordered arrangement that results in a cross-striation pattern along the length of the muscle fibers. Muscle fibers are grouped into fascicles, which are enwrapped by connective tissue sheet named endomysium. Each of muscle fiber is composed by the myofibrils encircled by the sheet of tubules—sarcoplasmic reticulum (SR). Individual muscle fibers are covered with the net of capillaries, which, in general, supply them with nutrients. The contraction of the fibers is initiated by the voluntary neurons and is regulated by the regulatory proteins and the calcium liberated from the SR cisternae. The basic contractile elements are the sarcomeres composed by the actin and myosin filaments. Both type of filaments have constant length and remind in the constant length irrespective of the state of contraction of the muscle. The mitochondria, distinguished by their location within muscle fibers as the subsarcolemmal (SS) and the interfibrillar (IFM) mitochondria, constitute the most important source of the adenosine triphosphate (ATP) for the muscle cells.