Principle of spiral arrangement of the skeletal muscles of humans and animals

It has been stated long ago, that smooth muscle elements in the vascular walls and other tubular systems in the human being and in the animals demonstrate spiral arrangement. The authors decided to show that there is a spiral formation of the skeletal musculature in the human being and in vertebrata at the level of the whole organism, its parts and separate muscles. By means of successive joining certain muscles, their parts and even separate groups of muscular fasciculi by tendons, aponeuroses, fascia and intermuscular septa, ligaments and bones kinematic chains of muscles have been revealed, those chains that have spiral direction regarding the longitudinal axes of the body and its parts. Two examples of left- and right-hand-screw types of spirals are presented and it is stressed that the spiral principle reflects biological symmetry of structural oppositions--enantiomorphism. A conclusion is made that the spiral form of the skeletal musculature is a universal regularity for the human being and for all vertebrata. The cylindric form of the vertebral body serves as a predestinated moment for this. The spiral twisting of the muscles is the most optimal for ensuring variability of movements and performing adaptive survival of the human being and animals in the Earth gravitational field.     

The myotendinous junction of the smooth feather muscles (mm. pennati)

Summary Smooth feather muscles (mm. pennati) consist of bundles of smooth muscle cells which are attached to the feather follicles by short elastic tendons. In addition, some muscle bundles are interrupted by elastic tendons. The elastic tendon is composed of longitudinally arranged elastic fibers which branch and wavy bundles of collagen fibrils. Smooth muscle cells of the muscle bundles are attached to each other by desmosome-like junctions and by fusion of the basal laminae. The cytoplasm of the muscle cells is characterized by conspicuous thick filaments and abundant thin and intermediate filaments. These are attached to band-like dense patches (dense bands) at the plasma membrane which are particularly broad at the tapering end of the muscle cell. The contact surface between smooth muscle cells and their elastic tendon is considerably increased (i) by deep finger-like invaginations and indentations located at the tapering muscle end, and (ii) by branching of the coarse elastic fibers into slender processes, which are attached to the richly folded surface of the muscle cell endings by peripheral microfibrils. This intimate interlocking closely resembles the myotendinous junctions in skeletal muscle. In addition to fibroblasts and fibrocytes, the myotendinous junction of the young growing chicks contains numerous so-called myofibroblasts, which are suggested to represent smooth muscle cells differentiating into fibroblasts of the developing tendon.Dedicated to Professor Dr. Helmut Leonhardt on the occasion of his 60th birthdaySupported by a grant from the Deutsche Forschungsgemeinschaft (Dr. 91/1)     

Fibrous framework of human skeletal muscles, fasciae and tendons

By means of scanning and transmissive electron microscopy, the construction of the fibrous framework of the human skeletal muscles, fasciae and tendons has been investigated and its morphofunctional analysis has been performed. The fibrous framework of the endomysium is presented as a complexly organized system of anastomosing fibers of the connective tissue, forming a net-like construction. The fibrous structures of the framework are united into a whole construction by connecting fibers and fibrils. Different types of structural interconnection of collagenous fibers with sarcolemma are revealed. The structure of the fibrous framework both in different muscles and within one muscle has certain peculiarities. The main constructive element of the fascial fibrous framework make large anastomosing collagenous fibers, their architectonics is stabilized by connective fibers and fibrils. The construction of the tendinous fibrous framework is characterized by a pronounced anisotropia of the largest collagenous fibers and a developed network of connective structures both on the surface and inside the collagenous fibers. Structural mechanisms, interconnecting muscles and tendons, are demonstrated. Presence of anastomoses between the fibrils in the composition of the collagenous fibers in the fascia and Achilles tendon are stated. Together with the peculiarities existing, the general principle of the structural organization of the fibrous framework of the muscle system is the net-like constructure dependent on presence of anastomoses and elements of the connective system between the fibrous structures. Depending on the organ's function, the construction of the network acquires certain specific morphological forms.     

Connective tissue structures of human skeletal muscle and their significance in the biomechanics of the body

By means of light optic and electron microscopy (SAM, TAM) histoconstruction of the connective tissue structures of the human skeletal muscles have been investigated and its analysis has been performed from biomechanical point of view. Fibrillar elements of the connective tissue are demonstrated to play an important role in structural adaptation of the skeletal muscle, as the organ, performing certain mechanical functions. The data obtained makes it possible to formulate the state, that the fibrillar network of the connective tissue is a polyfunctional system, that ensures integration of the structural elements of the muscle, transmission of mechanical strains, is the carcass of the organ and participates in formation of its buffer and amortizational mechanisms. The integration mechanisms of the main functional elements of the muscle belly, tendons and fascia to a great extent are of a unification character.     

The fin musculature of cuttlefish and squid (Mollusca, Cephalopoda): morphology and mechanics

The lateral fins of cuttlefish and squid consist of a tightly packed three-dimensional array of musculature that lacks bony skeletal support or fluid-filled cavities for hydrostatic skeletal support. During swimming and manoeuvring, the fins are bent upward and downward in undulatory waves. The fin musculature is arranged in three mutually perpendicular planes. Transverse muscle bundles extend parallel to the fin surface from the base of the fin to the fin margin. Dorso-ventral muscle bundles extend from dorsal and ventral connective tissue fasciae to a median connective tissue fascia. A layer of longitudinal muscle bundles is situated adjacent to both the dorsal and ventral surface of the median fascia. The muscle fibres are obliquely striated and include a core of mitochondria. A zone of muscle fibres with a more extensive core of mitochondria is present in both the dorsal and the ventral transverse muscle bundles. It is hypothesized that these muscle masses include two fibre types with different aerobic capacity. A network of connective tissue fibres is present in the transverse and dorso-ventral muscle masses. These fibres, probably collagen, are oriented at 45 to the long axes of the transverse and dorsoventral muscle fibres in transverse planes.
A biomechanicayl analysis of the morphology suggests that support for fin movements is provided by simultaneous contractile activity of muscles of specific orientations in a manner similar to that proposed for other 'muscular-hydrostats'. The musculature therefore provides both the force and support for movement. Connective tissue fibres may aid in providing support and may also serve for elastic energy storage.     

Experimental study of the influence of senescence in the biomechanical properties of the temporal tendon and deep temporal fascia based on uniaxial tension tests

The present study focuses on the determination of human temporal tendons and deep temporal fascia biomechanical behavior. The tensile and shear loads generated by the temporal muscle are transmitted to the masticatory system by the temporal tendons and muscle fascia. Establishing these connective tissues' biomechanical properties will help to develop proper finite element-based simulations of the human masticatory system, which will allow better understanding of diseases affecting the temporomandibular joint. The tissues were harvested from 8 male fresh cadavers, who were subjected to uniaxial tension tests. Available literature states that different connective tissues undergo identical biochemical, cellular and mechanical changes during senescence. Several mechanical phenomena occur during maturation, resulting in stiffer, stronger and more stable connective tissues, although less flexible. Based on this evidence, the present study suggests that older temporal tendon and fascia samples are stiffer than younger ones. We also found significant higher secant moduli with increasing age.     

Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish

Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression or activation of two proteins involved in anchoring the intracellular cytoskeleton to the extracellular matrix, Focal adhesion kinase (Fak) and beta-dystroglycan is up-regulated. Conversely, the extracellular matrix protein Fibronectin (Fn) is down-regulated. This degradation of Fn as fast-twitch fibers attach to the MTJ results in Fn protein defining a novel microenvironment within the MTJ adjacent to slow-twitch, but not fast-twitch, muscle. Interestingly, however, Fak, laminin, Fn and beta-dystroglycan concentrate at the MTJ in mutants that do not have slow-twitch fibers. Taken together, these data elucidate novel and dynamic microenvironments within the MTJ and indicate that MTJ morphogenesis is spatially and temporally complex.     

The relationship of the superficial and deep facial fascias: relevance to rhytidectomy and aging.

Controversy persists regarding the relationship of the superficial facial fascia (SMAS) to the mimetic muscles, deep facial fascia, and underlying facial nerve branches. Using fresh cadaver dissection, and supplemented by several hundred intraoperative dissections, we studied facial soft-tissue anatomy. The facial soft-tissue architecture can be described as being arranged in a series of concentric layers: skin, subcutaneous fat, superficial fascia, mimetic muscle, deep facial fascia (parotidomasseteric fascia), and the plane containing the facial nerve, parotid duct, and buccal fat pad. The anatomic relationships existing within the facial soft-tissue layers are (1) the superficial facial fascia invests the superficially situated mimetic muscles (platysma, orbicularis oculi, and zygomaticus major and minor); (2) the deep facial fascia represents a continuation of the deep cervical fascia cephalad into the face, the importance of which lies in the fact that the facial nerve branches within the cheek lie deep to this deep fascial layer; and (3) two types of relationships exist between the superficial and deep facial fascias: In some regions of the face, these fascial planes are separated by an areolar plane, and in other regions of the face, the superficial and deep fascia are intimately adherent to one another through a series of dense fibrous attachments. The layers of the facial soft tissue are supported in normal anatomic position by a series of retaining ligaments that run from deep, fixed facial structures to the overlying dermis. Two types of retaining ligaments are noted as defined by their origin, either from bone or from other fixed structures within the face.(ABSTRACT TRUNCATED AT 250 WORDS)     

Three-dimensional dynamical capabilities of the human masticatory muscles

Many habitual human jaw movements are non-symmetrical. Generally, it is observed that when the lower incisors move to one side the contralateral condyle moves forwards onto the articular eminence, whereas the ipsilateral condyle stays in the mandibular fossa, moving slightly to the ipsilateral side. These jaw movements are the result of contractions of active masticatory muscles and guided by the temporomandibular joints, their ligaments and passive elastic properties of the muscles. It is not known whether the movements are primarily dependent on passive guidance, active muscle control or both. Therefore, the objective of this study was to analyse the interplay between these factors during non-symmetrical jaw movements. A six-degrees-of-freedom dynamical biomechanical model of the human masticatory system was used. The movements were not restricted to a priori defined joint axes. Jaw movement simulations were performed by unilateral activity of the muscles. The ligaments or the passive elastic properties of the muscles could be removed during these simulations. Laterodeviations conform to naturally observed ones could be generated by unilateral muscle contractions. The movement of the lower incisors was hardly affected by the absence of passive elastic muscle properties or temporomandibular ligaments. The latter, however, influenced the movement of the condyles. The movements could be understood by analysing the combination of forces and torques with respect to the centre of gravity of the lower jaw. In addition, the loading of the condyles appeared to be an important determinant for the movement. This analysis emphasizes that the movements of the jaw are primarily dependent on the orientation of the contributing muscles with respect to this centre of gravity and not on the temporomandibular ligaments or passive elastic muscle properties.     

The locomotory system of pearlfish Carapus acus: What morphological features are characteristic for highly flexible fishes?

The body curvature displayed by fishes differs remarkably between species. Some nonmuscular features (e.g., number of vertebrae) are known to influence axial flexibility, but we have poor knowledge of the influence of the musculotendinous system (myosepta and muscles). Whereas this system has been described in stiff‐bodied fishes, we have little data on flexible fishes. In this study, we present new data on the musculotendinous system of a highly flexible fish and compare them to existing data on rigid fishes. We use microdissections with polarized light microscopy to study the three‐dimensional anatomy of myoseptal tendons, histology and immunohistology to study the insertion of muscle fiber types into tendons, and μ‐CT scans to study skeletal anatomy. Results are compared with published data from stiff‐bodied fishes. We identify four important morphological differences between stiff‐bodied fishes and Carapus acus: (1) Carapus bears short tendons in the horizontal septum, whereas rigid fishes have elongated tendons. (2) Carapus bears short lateral tendons in its myosepta, whereas stiff‐bodied fishes bear elongated tendons. Because of its short myoseptal tendons, Carapus retains high axial flexibility. In contrast, elongated tendons restrict axial flexibility in rigid fishes but are able to transmit anteriorly generated muscle forces through long tendons down to the tail. (3) Carapus bears distinct epineural and epipleural tendons in its myosepta, whereas these tendons are weak or absent in rigid fishes. As these tendons firmly connect vertebral axis and skin in Carapus, we consider them to constrain lateral displacement of the vertebral axis during extreme body flexures. (4) Ossifications of myoseptal tendons are only present in C. acus and other more flexible fishes but are absent in rigid fishes. The functional reasons for this remain unexplained. J. Morphol., 2012. © 2011 Wiley Periodicals, Inc.     

Double-layered free temporal fascia flap as a two-layered tendon-gliding surface

We report the use of a two-layered free fascial flap consisting of temporoparietal and deep temporal fascia based on a single vascular pedicle, the superficial temporal artery and vein. The flap was used to reconstruct an extensive degloving injury of the dorsum of the hand, in which multiple intact extensor tendons lay fully exposed on all sides, with exposed bone beneath them. By sandwiching the tendons between the layers of vascularized fascia, gliding surfaces were provided, both superficial and deep to the exposed tendons. The single-stage reconstruction was completed with a split-thickness skin graft. The patient returned to heavy manual work within 12 weeks of injury. He obtained an excellent range of movement without the need for tenolysis.     

Functional importance of a highly elastic ligament on the mammalian diaphragm.

The diaphragm of mammals is a musculotendinous dome separating the thoracic and abdominal cavities. With no skeletal elements to stretch it, the diaphragm has the problem of positioning its muscle fibres at a length appropriate for the onset of an inspiratory contraction. This is achieved through a negative intrapleural pressure, resulting from the opposing elastic recoil of the ribcage and lungs, which sucks the diaphragm into the thorax and extends the muscle fibres. A consequence of this negative pressure is that the diaphragm muscle is under tension when inactive during expiration. This is an unusual condition for skeletal muscles, which can suffer irreversible changes when stretched to long length, or they may respond by growing longer. We now describe a highly elastic and resilient diaphragmatic ligament which sets a sarcomere length enabling the muscle to use its full operating range, reduces stress on the diaphragm muscle fibres, and assists shortening of the diaphragm muscle at the onset of inspiration by means of elastic recoil.     

Muscle-driven finite element simulation of human foot movements

This paper describes a finite element scheme for realistic muscle-driven simulation of human foot movements. The scheme is used to simulate human ankle plantar flexion. A three-dimensional anatomically detailed finite element model of human foot and lower leg is developed and the idea of generating natural foot movement based entirely on the contraction of the plantar flexor muscles is used. The bones, ligaments, articular cartilage, muscles, tendons, as well as the rest soft tissues of human foot and lower leg are included in the model. A realistic three-dimensional continuum constitutive model that describes the biomechanical behaviour of muscles and tendons is used. Both the active and passive properties of muscle tissue are accounted for. The materials for bones and ligaments are considered as homogeneous, isotropic and linearly elastic, whereas the articular cartilage and the rest soft tissues (mainly fat) are defined as hyperelastic materials. The model is used to estimate muscle tissue deformations as well as stresses and strains that develop in the lower leg muscles during plantar flexion of the ankle. Stresses and strains that develop in Achilles tendon during such a movement are also investigated.     

Muscle-driven finite element simulation of human foot movements

This paper describes a finite element scheme for realistic muscle-driven simulation of human foot movements. The scheme is used to simulate human ankle plantar flexion. A three-dimensional anatomically detailed finite element model of human foot and lower leg is developed and the idea of generating natural foot movement based entirely on the contraction of the plantar flexor muscles is used. The bones, ligaments, articular cartilage, muscles, tendons, as well as the rest soft tissues of human foot and lower leg are included in the model. A realistic three-dimensional continuum constitutive model that describes the biomechanical behaviour of muscles and tendons is used. Both the active and passive properties of muscle tissue are accounted for. The materials for bones and ligaments are considered as homogeneous, isotropic and linearly elastic, whereas the articular cartilage and the rest soft tissues (mainly fat) are defined as hyperelastic materials. The model is used to estimate muscle tissue deformations as well as stresses and strains that develop in the lower leg muscles during plantar flexion of the ankle. Stresses and strains that develop in Achilles tendon during such a movement are also investigated.     

The role of tendon elasticity in the locomotion of the camel (Camelus dromedarius)

Several ofthe distal leg muscles ofcamels have very short or even rudimentary muscle fibres. This makes it possible to calculate the elastic extensions of tendons that occur in running, from the leg positions observed in films. A series of experiments have been performed for this purpose on the dissected legs of a camel. The initial conclusions derived from them are modified in the light of estimates of the forces that act on the tendons, and of measurements of the elastic properties of one tendon. Evidence for movement at the intertarsal and tarso-metatarsal joints. and the corresponding joints of the fore leg, is examined. The importance of the various tendons as elastic energy stores in running is assessed.     

Phylogenetic relationship of muscle tissues deduced from superimposition of gene trees.

Muscle tissues can be divided into six classes; smooth, fast skeletal, slow skeletal and cardiac muscle tissues for vertebrates, and striated and smooth muscle tissues for invertebrates. We reconstructed phylogenetic trees of six protein genes that are expressed in muscle tissues and, using a newly developed program, inferred the phylogeny of muscle tissues by superimposition of five of those gene trees. The proteins used are troponin C, myosin essential light chain, myosin regulatory light chain, myosin heavy chain, actin, and muscle regulatory factor (MRF) families. Our results suggest that the emergence of skeletal-cardiac muscle type tissues preceded the vertebrate/arthropod divergence (ca. 700 MYA), while vertebrate smooth muscle seemed to evolve independent of other muscles. In addition, skeletal muscle is not monophyletic, but cardiac and slow skeletal muscles make a cluster. Furthermore, arthropod striated muscle, urochordate smooth muscle, and vertebrate muscles except for smooth muscle share a common ancestor. On the other hand, arthropod nonmuscle and vertebrate smooth muscle and nonmuscle share a common ancestor.     

The integrated function of muscles and tendons during locomotion

The mechanical roles of tendon and muscle contractile elements during locomotion are often considered independently, but functionally they are tightly integrated. Tendons can enhance muscle performance for a wide range of locomotor activities because muscle-tendon units shorten and lengthen at velocities that would be mechanically unfavorable for muscle fibers functioning alone. During activities that require little net mechanical power output, such as steady-speed running, tendons reduce muscular work by storing and recovering cyclic changes in the mechanical energy of the body. Tendon stretch and recoil not only reduces muscular work, but also allows muscle fibers to operate nearly isometrically, where, due to the force-velocity relation, skeletal muscle fibers develop high forces. Elastic energy storage and recovery in tendons may also provide a key mechanism to enable individual muscles to alter their mechanical function, from isometric force-producers during steady speed running to actively shortening power-producers during high-power activities like acceleration or uphill running. Evidence from studies of muscle contraction and limb dynamics in turkeys suggests that during running accelerations work is transferred directly from muscle to tendon as tendon stretch early in the step is powered by muscle shortening. The energy stored in the tendon is later released to help power the increase in energy of the body. These tendon length changes redistribute muscle power, enabling contractile elements to shorten at relatively constant velocities and power outputs, independent of the pattern of flexion/extension at a joint. Tendon elastic energy storage and recovery extends the functional range of muscles by uncoupling the pattern of muscle fiber shortening from the pattern of movement of the body.     

A control theoretic model of the forearm

In this paper, a control theoretic model of the forearm is developed and analyzed, and a computational method for predicting muscle activations necessary to generate specified motions is described. A detailed geometric model of the forearm kinematics, including the carrying angle and models of how the biceps and the supinator tendons wrap around the bones, is used. Also, including a dynamics model, the final model is a system of differential equations where the muscle activations play the role of control signals. Due to the large number of muscles, the problem of finding muscle activations is redundant, and this problem is solved by an optimization procedure. The computed muscle activations for ballistic movements clearly recaptures the triphasic ABC (Activation-Braking-Clamping) pattern. It is also transparent, from the muscle activation patterns, how the muscles cooperate and counteract in order to accomplish desired motions. A comparison with previously reported experimental data is included and the model predictions can be seen to be partially in agreement with the experimental data.