The movement systems: skeletal and muscular
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Three types of muscle tissue can be found within the body: smooth, cardiac and skeletal muscle (Figure 5.8). Muscle tissues, and the cells or fibres from which they are formed, are responsible for bringing about movement, whether it be movement of the body for playing sport, circulation of blood and nutrients around the body or the propulsion of foods through the digestive tract. The structure of each muscle tissue type differs according to its function. Smooth muscle is found throughout the body. It surrounds the blood vessels and airways and serves to assist with the passage of blood and air through the cardiovascular and respiratory systems. It is also part of the digestive tract walls where its contractions assist the movement of food along it. Smooth muscle, in common with cardiac muscle, is innervated by the autonomic nervous system and so we have little or no voluntary control over the contraction of these muscle groups. We cannot make the heart beat faster or push food through the digestive tract more quickly. Cardiac muscle, the muscle which forms the heart, is responsible for our heart beat and the subsequent pumping of blood and nutrients around the body. Skeletal muscle is the only muscle type that can be voluntarily contracted and is the form of tissue that enables bodily movement by contracting against the skeleton (hence the name). The human body is comprised of between 600 and 700 muscles which vary in size from 1 mm (such as those found attached to the bones of the ear) to 30 cm long in the sartorius muscle of the thigh.
Effects of introducing gap constraints in the masticatory system: A finite element study
J. Belinha, R.M. Natal Jorge, J.C. Reis Campos, Mário A.P. Vaz, João Manuel, R.S. Tavares in Biodental Engineering V, 2019
The jaw muscles present in our model are the lateral pterygoid, digastric, masseter, temporalis and medial pterygoid. Muscles are composed by two entities, one representing the fibrous part and the other the tendon. Hill’s muscle model was employed to represent the fibers and an inextensible wire to represent the tendons, because they undergo very small deformation and may, for this reason, be ignored. In total, eight truss elements represent the following muscles (on each side): Anterior and posterior temporalis, superficial and deep masseter, superior and inferior lateral pterygoid, medial pterygoid and digastric. Muscle fibers are composed by myofibrils. In the case of striated muscles, the myofibrils are arranged into contractile units called sarcomeres. Forces produced by this type of muscle are influenced by the length of their sarcomeres (force-length relationship) and their contraction velocities (force-velocity relationship). Additionally, the muscle exhibits a passive elastic force when stretched. In our model, the characteristic curves of the muscle are taken from van Ruijven & Weijs (1990).
Skeletal Muscle
Nassir H. Sabah in Neuromuscular Fundamentals, 2020
A skeletal muscle is basically a grouping of several thousand to several million individual muscle fibers of 10–100 µm diameter and of length in the range of one millimeter or so in the smallest skeletal muscle, the stapedius muscle of the inner ear, but can be as long as 60 cm in the human sartorius muscle that extends obliquely over the thigh. Although they are often described as single muscle cells, individual muscle fibers are in fact formed during embryonic development from the fusion of progenitor cells known as myoblasts. They are therefore multinucleated, with hundreds to thousands of nuclei in longer fibers. Muscle fibers are typically cylindrical in shape, circular or oval in cross section, with conical ends. It is estimated that the human body contains more than 108 muscle fibers. Muscle fibers are also known as myocytes or myofibers.
Developments with 3D bioprinting for novel drug discovery
Published in Expert Opinion on Drug Discovery, 2018
Aishwarya Satpathy, Pallab Datta, Yang Wu, Bugra Ayan, Ertugrul Bayram, Ibrahim T. Ozbolat
The muscle tissues have a very complex structure comprising various kinds of cell types and different mechanical properties exhibiting contractile force. Various bioprinting approaches have been thus established to closely mimic the complex anatomy of muscle. Murine C2C12 cells were mixed with alginate/Pluronic bioink to create muscle constructs in vitro using EBB. These 3D constructs have been used in several studies of drug testing based on the measurement of contractile force, and cell viability of above 80% was observed, along with the substantial amount of myogenic differentiation indicated by the positive expression of myogenic markers such as MyoD, Myogenin, and alpha-sarcomeric actin [87]. Use of skeletal-muscle-derived bioink can provide enhanced potential for fabricating biomimetic muscle constructs [88]. In vitro muscle models will have enhanced applicability for the testing of drugs, such as cardiotoxin, against muscle injuries [89], muscular dystrophy [90], or for evaluating the absorption of drugs intended to be developed as intramuscular injections for depot action [91].
In vitro differentiation of progenitor cells isolated from juvenile pig hearts – expression of relevant gene and protein markers
Published in Scandinavian Cardiovascular Journal, 2018
Simon Limbrecht Mogensen, Martin Krøyer Rasmussen, Niels Oksbjerg, Jette Feveile Young, Jens Rolighed Larsen
The adult heart is composed of several different types of tissues, including smooth muscle, endothelial and connective tissues. Earlier investigations of CPCs showed them to be multipotent, with the capacity to differentiate towards smooth muscle and endothelial lineages in addition to the cardiomyocyte lineage [16]. VWF and SMA are specific markers of endothelial and smooth muscle cells, respectively, and both VWF and SMA mRNAs were expressed in the PCs. SMA expression significantly decreased during both the proliferation and differentiation of the PCs. Interestingly, smooth muscle actin protein was expressed post-differentiation of these cells. The demonstration of their SMA protein expression suggests a smooth muscle commitment, and the decrease in SMA gene expression could well be explained by a downregulation of SMA mRNA expression occurring when a significant level of smooth muscle actin protein had been produced in the cells.
Effect of muscle distribution on lung function in young adults
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Wenbo Shu, Mengchi Chen, Zhengyi Xie, Liqian Huang, Binbin Huang, Peng Liu
A prolonged state of decline in VC results in hindered muscle function of the limbs, atrophy, weakness, and reduction of oxidative capacity (Bui et al. 2019; Shah et al. 2019). Swallow et al. found that the strength of the quadriceps muscle can predict the mortality of patients with moderate to severe COPD (Swallow et al. 2007). In addition to increasing the strength of the breathing muscles, exercise and training of the limbs can also enhance the contractility of the diaphragm, improve the elasticity of the thorax and alveoli, and improve lung compliance (Haas et al. 1985). All of the above are the correlation studies between lung function and limb function in patients with lung diseases. A strong positive correlation also exists between the strength of the flexor and extensor muscles of the lower limbs and the strength of the respiratory muscles in healthy people. The joint development of these parameters is conducive to improving the performance of athletes (Akınog˘Lu et al. 2019). Amann et al. (2010) found that the central brain commands, and the afferent feedback from the muscles of the limbs interact with each other, affecting the cardiopulmonary response. As such, limb function and respiratory function are closely related and affect the size of lung capacity. The role of limb muscle tissue is important.
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