Functional morphology of the endomysium in series fibered muscles
TL;DR: It is demonstrated that a high proportion of the collagen fibrils will be curvilinear at all sarcomere lengths, and the organization of endomysial collagen is appropriate for the transfer of loads between myofibers by means of shear.
Abstract: Many skeletal muscles, including the feline biceps femoris, are composed of short, tapered myofibers arranged in an overlapping longitudinal series. The endomysium of such muscles transfers tension between overlapping myofibers, and is thus an elastic element in series with them. The endomysium of the cat biceps femoris contains curvilinear collagen fibrils in an approximately isotropic (random) array. The collagen fibrils undergo only a modest reorientation as the myofibers shorten or lengthen within the physiological range. A geometrical model predicts no change in the thickness of the endomysium on changing muscle fiber length and quantifies the expected collagen fibril reorientation in the endomysium as a function of muscle extension. It is also demonstrated that a high proportion of the collagen fibrils will be curvilinear at all sarcomere lengths. The organization of endomysial collagen is appropriate for the transfer of loads between myofibers by means of shear.
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TL;DR: Full understanding of these physiological processes will provide the physiological basis for understanding of tissue overloading and injury seen in both tendons and muscle with repetitive work and leisure time physical activity.
Abstract: The extracellular matrix (ECM), and especially the connective tissue with its collagen, links tissues of the body together and plays an important role in the force transmission and tissue structure maintenance especially in tendons, ligaments, bone, and muscle. The ECM turnover is influenced by physical activity, and both collagen synthesis and degrading metalloprotease enzymes increase with mechanical loading. Both transcription and posttranslational modifications, as well as local and systemic release of growth factors, are enhanced following exercise. For tendons, metabolic activity, circulatory responses, and collagen turnover are demonstrated to be more pronounced in humans than hitherto thought. Conversely, inactivity markedly decreases collagen turnover in both tendon and muscle. Chronic loading in the form of physical training leads both to increased collagen turnover as well as, dependent on the type of collagen in question, some degree of net collagen synthesis. These changes will modify the mechanical properties and the viscoelastic characteristics of the tissue, decrease its stress, and likely make it more load resistant. Cross-linking in connective tissue involves an intimate, enzymatical interplay between collagen synthesis and ECM proteoglycan components during growth and maturation and influences the collagen-derived functional properties of the tissue. With aging, glycation contributes to additional cross-linking which modifies tissue stiffness. Physiological signaling pathways from mechanical loading to changes in ECM most likely involve feedback signaling that results in rapid alterations in the mechanical properties of the ECM. In developing skeletal muscle, an important interplay between muscle cells and the ECM is present, and some evidence from adult human muscle suggests common signaling pathways to stimulate contractile and ECM components. Unaccostumed overloading responses suggest an important role of ECM in the adaptation of myofibrillar structures in adult muscle. Development of overuse injury in tendons involve morphological and biochemical changes including altered collagen typing and fibril size, hypervascularization zones, accumulation of nociceptive substances, and impaired collagen degradation activity. Counteracting these phenomena requires adjusted loading rather than absence of loading in the form of immobilization. Full understanding of these physiological processes will provide the physiological basis for understanding of tissue overloading and injury seen in both tendons and muscle with repetitive work and leisure time physical activity.
1,365 citations
TL;DR: The basic architectural properties of human upper and lower extremity muscles are described and the ability of muscles to change their architecture in response to immobilization, eccentric exercise, and surgical tendon transfer is reviewed.
Abstract: Skeletal muscle architecture is the structural property of whole muscles that dominates their function. This review describes the basic architectural properties of human upper and lower extremity muscles. The designs of various muscle groups in humans and other species are analyzed from the point of view of optimizing function. Muscle fiber arrangement and motor unit arrangement is discussed in terms of the control of movement. Finally, the ability of muscles to change their architecture in response to immobilization, eccentric exercise, and surgical tendon transfer is reviewed. Future integrative physiological studies will provide insights into the mechanisms by which such adaptations occur. It is likely that muscle fibers transduce both stress and strain and respond by modifying sarcomere number in a way more suited to the new biomechanical environment.
1,015 citations
Cites background from "Functional morphology of the endomy..."
...Fibers may terminate within the muscle belly in the complex extracellular matrix composed of endomysial connective tissue.(62) These connective tissues merge into a final “external tendon” where force can be applied FIGURE 4....
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TL;DR: The structure, composition, and mechanical properties of skeletal muscle ECM are reviewed; the cells that contribute to the maintenance of the ECMAreas for future study are proposed; and overview changes that occur with pathology are described.
Abstract: The skeletal muscle extracellular matrix (ECM) plays an important role in muscle fiber force transmission, maintenance, and repair. In both injured and diseased states, ECM adapts dramatically, a property thathas clinical manifestations and alters muscle function. Here, we review the structure, composition, and mechanical properties of skeletal muscle ECM, describe the cells that contribute to the maintenance of the ECM and, finally, overview changes that occur with pathology. New scanning electron micrographs of ECM structure are also presented with hypotheses about ECM structure-function relationships. Detailed structure-function relationships of the ECM have yet to be defined and, as a result, we propose areas for future studies.
737 citations
Cites background from "Functional morphology of the endomy..."
...An exception to the casual sampling performed in most ECM studies is the systematic and quantitative description of the muscle endomysial ECM reported for feline and bovine muscle by Purslow and Trotter.(2,3) They showed that a highly ordered network surrounds individual muscle fibers that deforms nonlinearly with increasing sarcomere length....
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...An exception to the casual sampling performed in most ECM studies is the systematic and quantitative description of the muscle endomysial ECM reported for feline and bovine muscle by Purslow and Trotter.2,3 They showed that a highly ordered network surrounds individual muscle fibers that deforms nonlinearly with increasing sarcomere length....
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TL;DR: It is hypothesised that definition of muscle fascicle size and shape by the bounding perimysium is related to the need for sub-sections of the whole muscle to slip past each other in the normal contractile function of the tissue.
406 citations
Cites background from "Functional morphology of the endomy..."
...Endomysial connective tissue facilitates load sharing within a fascicle by linking adjacent muscle cells by shear (Trotter & Purslow, 1992; Purslow & Trotter, 1994; Trotter et al, 1995)....
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TL;DR: Evidence from experiments involving tenotomy, fasciatomy and aponeurotomy regarding its importance is presented, implications for thinking about muscle(s) and movement are considered and they are considered to be stronger than direct tensile transmission.
400 citations
Cites background or methods from "Functional morphology of the endomy..."
...However, it was not until the SEM images of Trotter and Purslow (Purslow and Trotter, 1994; Trotter and Purslow, 1992) that some of the real excitement of a new vision was introduced....
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...The endomysium was modeled using geometrical models (Trotter and Purslow, 1992) and collagen fiber directions studied....
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...On the basis of morphological work as well as biomechanical modeling, Trotter and co-workers made very significant contributions to our understanding of some of the processes of force transmission within this type of muscle (Trotter, 1991, 1990; Trotter and Purslow, 1992; Purslow and Trotter, 1994)....
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References
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01 Jan 2008
TL;DR: The combination of materials to form a new material system with enhanced material properties is a well documented historical fact as discussed by the authors, which is why many artisans from the Mediterranean and Far East used a form of composite technology in molding art works which were fabricated by layering cut paper in various sizes for producing desired shapes and contours.
Abstract: The combination of materials to form a new material system with enhanced material properties is a well documented historical fact. For example, the ancient Jewish workers during their tenure under the Pharaohs used chopped straws in bricks as a means of enhancing their structural integrity. The Japanese Samurai warriors were known to use laminated metals in the forging of their swords to obtain desirable material properties. Even certain artisans from the Mediterranean and Far East used a form of composite technology in molding art works which were fabricated by layering cut paper in various sizes for producing desired shapes and contours.
3,908 citations
Book•
01 Jan 2008TL;DR: The authors provides both scientists and engineers with all the information they need to understand composite materials, covering their underlying science and technological usage, including surface coatings, highly porous materials, bio-composites and nano-com composites, as well as thoroughly revised chapters on fibres and matrices.
Abstract: This fully expanded and updated edition provides both scientists and engineers with all the information they need to understand composite materials, covering their underlying science and technological usage It includes four completely new chapters on surface coatings, highly porous materials, bio-composites and nano-composites, as well as thoroughly revised chapters on fibres and matrices, the design, fabrication and production of composites, mechanical and thermal properties, and industry applications Extensively expanded referencing engages readers with the latest research and industrial developments in the field, and increased coverage of essential background science makes this a valuable self-contained text A comprehensive set of homework questions, with model answers available online, explains how calculations associated with the properties of composite materials should be tackled, and educational software accompanying the book is available online An invaluable text for final-year undergraduates in materials science and engineering, and graduate students and researchers in academia and industry
2,746 citations
450 citations
TL;DR: Splinted fibers from frog semitendinosus muscle were used to study mechanical connections (transverse coupling) between myofibrillar components and sarcolemma and found that the transverse coupling is strong enough to insure a tight correlation between my ofibril length and overlying sarCOlemma length in both resting and activated fibers and to transmit nearly maximum isometric tension to the splint.
Abstract: The extensibility of the sarcolemma of single myofibers can be reduced locally by leaving a segment covered by a sleeve of surrounding tissue composed of cut myofibers, blood vessels, and connective tissue, hereafter referred to as "the splint" Splinted fibers from frog semitendinosus muscle were used to study mechanical connections (transverse coupling) between myofibrillar components and sarcolemma The transverse coupling is strong enough to insure a tight correlation between myofibril length and overlying sarcolemma length in both resting and activated fibers and to transmit nearly maximum isometric tension to the splint Lateral transmission of active tension was demonstrated with a preparation which had the distal two-thirds of an intact fiber covered by a splint and the proximal third dissected clean When the outer end of the splint was pinned down and only the distal tendon was held, tension generated in the splinted fiber was transmitted to, and recorded from, the splint Parameters of isometric tension transmitted laterally were not significantly different from those of tension transmitted longitudinally Myofibrils branch profusely and form a network that may act as a unitary force generator and transmitter In splinted fibers its output is possibly picked up circumferentially and transmitted across the sarcolemma by a microfilament network A cap of relatively inextensible sarcolemma "splints" myofiber ends Resting tension is transmitted to and from the myofibrils by transverse coupling beyond the cap and the region of short sarcomere spacing it covers Transverse cytoskeletal connections at Z and M regions are described Immobilization of the sarcolemma allows study of myofibril-sarcolemma linkage in intact fibers Both active and resting tension were transmitted laterally
399 citations
TL;DR: The arrangement and distribution of connective tissue in six different skeletal muscles and smooth muscle was examined by scanning electron microscopy to explain differences in the mechanical properties of the different muscle.
Abstract: The arrangement and distribution of connective tissue in six different skeletal muscles and smooth muscle was examined by scanning electron microscopy. The endomysial arrangement of collagen was similar in all types of muscle and consisted of three components: (1) myocyte-myocyte connectives; (2) myocyte-capillary connectives; and (3) a weave network of collagen intimately associated with the basal laminae of the myocytes. The perimysium of the different muscles was qualitatively similar but quantitatively dissimilar. The perimysium consisted consisted of large tendon-like bundles of interwoven collagen which connected with the dense weave collagen that surrounded groups of muscles. The arrangement of the collagen in the perimysium and endomysium would explain differences in the mechanical properties of the different muscle. The contribution of the connective tissue to mechanical properties of muscle is discussed.
358 citations