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Neuromuscular Physiology
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
A whole muscle consists of about 85% muscle fibers and approximately 15% connective tissue. The connective tissue organizes the muscle and provides shaped. Connective tissue is composed of a ground substance, collagen, reticular and elastin fibers in various proportions. The proportions of these constituents depend upon a number of factors including the muscle’s function, training, and nutritional factors. Importantly, the connective tissue is largely responsible for force transmission (Ft). Indeed, forces created at the sarcomere level are largely transmitted to the lever system (bones) by a series of connective tissues terminating in the tendon-bone interface. The degree of elasticity and distensibility of the connective tissue (and the muscle) helps to ensure that the tension developed by the muscle is efficiently transmitted and that the muscle will return to its original shape after being shortened or stretched. So, it is the connective tissue of muscle that provides a conceptual framework for the series and parallel elastic components within a muscle. As a result of passive stretching or active contraction the initial tension created is primarily a result of the elastic properties of the connective tissue. During a shortening or lengthening contraction, the muscle cannot develop force or perform work against a resistance until the elastic components are stretched to the point that muscle tension and the resistance (load) are in equilibrium.
Functional Anatomy
Published in James Crossley, Functional Exercise and Rehabilitation, 2021
Collagen fibers act like tough threads, providing tensile strength, supporting and binding tissues together. Elastin is a rubber-like substance designed to resist distension, absorb load and recoil after stretch. Ground substance, a lubricating gel composed of proteoglycans, hyaluronic acid and water contains various cells, including fibroblasts that synthesize collagen and maintain the extracellular matrix. Fibroblasts play a critical role in wound healing by maintaining the health of connective tissue cells.
Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The dermal ground substance shows little change with aging. Changes seem to occur in the young and then very little change is seen throughout life.199 Jarrett reports that Loewi and Meyer found an increase in dermatan sulfate, hyaluronate and chondroitin sulfate in the adult pig in comparison with the embryonic pig.201 The function of the ground substance is to maintain the homeostatic environment for cells and fibers. Also, it is thought to play a role in limiting the spread of bacteria because of its viscosity.199,202
Anatomic variations of the human falx cerebelli and its association with occipital venous sinuses
Published in British Journal of Neurosurgery, 2021
Safiye Çavdar, Bilgehan Solmaz, Özgül Taniş, Orhan Ulas Guler, Hakkı Dalçık, Evren Aydoğmuş, Leyla Altunkaya, Erdoğan Kara, Hızır Aslıyüksek
Falx cerebelli, is composed of fibroelastic, dense irregular connective tissue. The connective tissue consisted of cells predominantly of fibroblast which produced the ground substance and collagen fibers. Additionally, the connective tissue contained sensory nerve endings and blood vessels. The arterioles were composed of 1–2 layers of smooth muscle cells in the tunica media and the venules were composed of a single layer of endothelium with many erythrocytes in their lumens (Figure 10a). Furthermore, a large number of lymphatic vessels appeared to be undulated with a single layer of endothelium and a subendothelial layer (Figure 10b). Extravagated lymphocytes surrounding the lymphatic vessels were observed (Figure 10b). Near the vessels, a peripheral nerve characteristically formed a round bundle of nerve processes surrounded by connective tissue sheath perineurium was detected (Figure 10a).
Comparison of dynamic response of three TLIF techniques on the fused and adjacent segments under vibration
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
A three-dimensional nonlinear finite element model of the intact L1–L5 lumbar spine was used in this study. The geometry of the spine was obtained by computer scanning tomographic specimens. The model mainly includes vertebrae, intervertebral discs, endplates, and various ligaments, as shown in Figure 1. Each vertebral body is composed of the outer 0.5–1.0 mm cortical bone and the inner cancellous bone. The intervertebral disc consists of the annular matrix, annulus fibrosus, and nucleus pulposus. The annulus ground substance (AGS), consisting of six fiber layers, encloses the nucleus pulposus. The Young’s modulus of the fiber ring decreases proportionally from the outer layer to the inner layer. There is a 0.5 mm thick endplate between the vertebral body and the intervertebral disc (Figure 1). The lumbar ligaments are active in tension only. The facet joint was modeled by surf-to-surf. The material properties were assumed to be homogeneous and isotropic, and the data were adopted from the literature (Wu and Ya 1976; Goel et al. 2007; Tsai et al. 2016; Guo and Li 2020) and are given in Table 1.
Parameter identification for the simulation of the periodontal ligament during the initial phase of orthodontic tooth movement
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Albert Heinrich Kaiser, Ludger Keilig, Reinhard Klein, Christoph Bourauel
In general, a ligament is a soft tissue that connects bone to bone and its mechanical function is to guide and restrict relative motion of joints. For an introduction refer to the textbook of Cowin and Doty (2007). Tensile tests of ligaments are typically done with specimens, where collagen fibre axes are aligned with the load direction. The stress strain curve observed depicts a progressive behaviour and is typically divided into three regions (e.g., Holzapfel 2001): At first, in the toe region, small force levels are necessary to elongate the tissue initially. Then, in the heel region, with increased load a progressively increased force is observed. The crimped collagen fibres gradually line up with load direction and at the end of the heel region, when collagen fibres are straightened, a transition into the linear region is observed. Here the stress strain curve is dominated by the straightened collagen fibres. At the end of the linear region, with gradual failure of highly stretched fibre bundles, drops in the stress strain curve and ultimate failure is observed. When subject to dynamic loads ligaments show viscoelastic behaviour. This could be due to the shear interaction of the interfibre matrix, that is, the interaction of the collagen fibres with the ground substance proteoglycans.