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Skeletal Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The cell membrane of the muscle fiber is the sarcolemma and has the ionic properties characteristic of excitable cells, manifested as a resting membrane voltage of about –90 mV and the ability to generate and propagate a muscle action potential. The sarcolemma is coated on the outside by a basement membrane formed largely of glycoproteins, and each muscle fiber is surrounded by a delicate layer of connective tissue, the endomysium (Figure 9.1). Groups of about 10 to more than 100 muscle fibers are bundled together into fascicles, the number of muscle fibers in a fascicle being larger in muscles that produce greater force, with less fineness of control. Fascicles are surrounded, in turn, by another layer of connective tissue, the perimysium. The whole muscle is ensheathed by a dense layer of irregular connective tissue, the epimysium.
The Functional Role of Extracellular Matrix
Published in Claudio Migliaresi, Antonella Motta, Scaffolds for Tissue Engineering, 2014
Eleonora Carletti, Matteo Stoppato, Claudio Migliaresi, Antonella Motta
In particular, collagen types I, III, IV, V, VI, XI, XII, XIV, XV, and XVIII are expressed during skeletal muscle development, while fibrillar types I and III predominate in adult endo-, peri-, and epimysium. Collagen type I is predominant in perimysial, whereas collagen type III is more distributed between endomysium and epimysium. However, it is still not well studied if collagen ratios differ in muscles with different functions. Type V collagen, another fibril-forming collagen, combines with types I and III forming, in perimysium and endomysium, a core for type I collagen fibrils. Types XII and XIV collagen are FACITs mainly found in perimysium.
A Review of the Technologies and Methodologies Used to Quantify Muscle-Tendon Structure and Function
Published in Cornelius Leondes, Musculoskeletal Models and Techniques, 2001
Skeletal muscle exists in a variety of shapes and sizes. It is composed of many subunits arranged in an organized, but complex manner (see Fig. 6.1). Additionally, muscles connect in series to tendons, are innervated by nerves, and supplied with vascular networks. A whole muscle is surrounded by a strong sheath called the epimysium, and divided into a variable number of subunits called fasciculi. Each fasciculus is surrounded by a connective tissue sheath called the perimysium. Fascicles may be further divided into bundles of fibers (or muscle cells) surrounded by a connective tissue sheath called the endomysium.8,26,51,54,88,91,108,109,110 Beneath the endomysium are two additional membranes, the basal lamina and the plasmalemma.26,88,96 The orientation of fibers relative to the line of action of the muscle-tendon complex is referred to as the pinnation angle. In humans, the pinnation angle ranges from 0 to 25°.88,121 Muscle may be classified as fusiform (or spindle), penniform, bipenniform, triangular, rectangular (or strap), and rhomboidal. Fibers attach at both ends to tendon or other connective tissue. Muscle fibers contain mitochondria, multiple nuclei, ribosomes, soluble proteins, lipids, glycogen, and satellite cells. Fibers are cylindrical, with their diameter ranging from 10 micrometers (μm) to 100 μm (smaller than the size of a human hair).88 They may be a few millimeters (mm) or many centimeters (cm) in length. Fibers are subdivided radially into myofibrils having diameters of approximately 1 μm. Myofibrils are divided longitudinally into sarcomeres and radially into myofilaments. A saromere is defined as the region between Z-lines (defined below). Sarcomeres have a rest length of about 2.0 to 3.0 μm. Myofilaments are often classified as either thick or thin filaments.
Effects of acai supplementation (Euterpe precatoria Mart) on muscle recovery markers after jump protocol
Published in Research in Sports Medicine, 2023
Tallyne Mayara Pacheco Dos Reis, Gabriel Gomes Aguiar, Luma Palheta de Azevedo, Emerson Silva Lima, Rodolfo André Dellagrana, Mateus Rossato
Muscle quality assessed by echo-intensity was determined for the Vastus Lateralis (VL), Rectus Femoris (RF), and Medial Gastrocnemius (GM) muscles. Three US images were obtained for each muscle with the subject at rest. For the acquisition of the GM images, the participants remained in the prone position, and for VL and RF the supine position was maintained, with the knee fully extended. The US probe was covered with water-soluble transmission gel and positioned longitudinally to the muscle fibres and perpendicular to the skin at 50% (RF, VL) and 30% (GM) of the distance between the popliteal sulcus and the lateral malleolus (Geremia et al., 2018). The US probe was fitted on the surface of the skin, parallel to the superficial and deep aponeuroses, and aligned with the hyperechoic perimysium intramuscular connective tissue. Probe alignment was considered adequate when the superficial and deep aponeuroses were parallel and multiple fascicles could be easily delineated without interruption in the image (Baroni et al., 2013). The US images were analysed using Image J software (straight line, line colour: yellow, version 1.48 v, National Institutes of Health, Bethesda, MA, United States). The eco-intensity (EI) was ascertained according to Caresio et al. (2014), obtaining the average of the muscles in grey scale and the mean EI was determined using a standard greyscale histogram function and expressed as a value between 0 (black) and 255 (white).
Spectroscopic imaging: Nuclear magnetic resonance and Raman spectrometry for the detection of collagen cross-linking from giant squid mantle, fin, and tentacle tissues
Published in Instrumentation Science & Technology, 2018
Héctor M. Sarabia-Sainz, Wilfrido Torres-Arreola, Josafat Marina Ezquerra-Brauer
The pyridinoline content varies broadly with the type of tissue and its sparse occurrence makes detection very difficult.[12] In fish muscle, collagen exists in endomysium, perimysium, and myocommata. Myocommata is required for much physical strength because it must connect myomeres continuously. However, endomysium might be not required for such physical strength.[10] Therefore, because the required strength is different depending on site location, collagens with several concentrations of pyridinoline might exist. Moreover, pyridinoline crosslinks would have a close relationship to collagen solubility.[5,10] Consistent with this, a considerable amount of pyridinoline predominates in insoluble collagens, rather than soluble ones, as detected in several squid species.[5]
Aponeurosis behaviour during muscular contraction: A narrative review
Published in European Journal of Sport Science, 2018
The aponeurosis and tendon are seamlessly connected within and outside the muscle belly through a connective tissue network, which surrounds muscle fibres (endomysium), groups of muscle fibres (perimysium) and whole muscles (epimysium) (Purslow, 2010). The means by which transverse forces are transmitted to the aponeurosis and surrounding muscles (Maas & Finni, 2018) are presumably through this connective tissue network (Street, 1983), which is stressed as muscle fibres are activated and fluid pressures within and outside the muscle’s fascial compartment increase during contraction (Aratow et al., 1993; Ateş et al., 2018; Reinhardt, Siebert, Leichsenring, Blickhan, & Böl, 2016). Longitudinal force transmission seemingly occurs through the same network and mechanism, as increasing muscle fluid volume has been shown to increase passive force by interacting with surrounding collagen fibres (Sleboda & Roberts, 2017). It has been shown that the arrangement of the collagen fibres within the endomysium and perimysium allows their geometry to vary as a function of muscle length, such that radial expansion of muscle fibres can be resisted at short lengths (Azizi, Deslauriers, Holt, & Eaton, 2017; Gindre, Takaza, Moerman, & Simms, 2013) and longitudinal stretch of the muscle fibres can be resisted at long lengths (Gindre et al., 2013; Purslow, 1989; Purslow & Trotter, 1994). Collagen fibres of the endomysium are connected to collagen fibres of the perimysium and are expected to be constituents of the tendon (Huijing, 1999), which emphasises the continuity of the connective tissue network and force transmission pathways from the muscle fibres to the tendon. Collagen fibres at the ends of muscle fibres can also transmit force to the tendon through the myotendinous junction, whereby the sarcolemma folds extensively in the direction of muscle fibres (Huijing, 1999) and collagen fibres from both the muscle fibres and aponeurosis are linked in an interdigitated fashion (Huijing, 1999; Maas & Finni, 2018).