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The cell and tissues
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
We are all familiar with skeletal muscle (often referred to as striated muscle because of the patterns that are seen when the muscle is examined under a microscope). This type of muscle is also known as voluntary muscle because we are able to control its activity. The cells of skeletal muscle are long and thin with multiple nuclei. They are gathered into bundles that are then bundled together, similar to multicore electrical cables. The muscle fibres, however, are able to contract and extend. You can easily demonstrate this by looking at the biceps muscle of the upper arm. As you flex your elbow the biceps muscle on the upper arm bulges up and as you straighten your arm the muscle flattens again. This process is complex and involves a number of elastic proteins and a very precise balance and exchange of electrolytes, especially calcium and magnesium.
Basic medicine: physiology
Published in Roy Palmer, Diana Wetherill, Medicine for Lawyers, 2020
Muscle cells are also excitable by electrical, chemical or physical stimuli. Their contraction is activated by the action potential conveyed down the relevant nerve. There are three different types of muscle. Striated muscle makes up the mass of musculature that moves the skeleton and is under voluntary control; its cross-striations give a characteristic striped appearance under the microscope. Filaments of contractile proteins—actin and myosin—undergo shortening when the muscle is stimulated to contract. Smooth muscle lacks striations, and its contraction is involuntary. It is typically found in the wall of the gut where it undergoes spontaneous activity, but it is also under the control of the autonomic nervous system. Cardiac muscle is also striated; it is only found in the heart, where it contracts rhythmically without the need for external stimulation.
Peripheral muscles
Published in Claudio F. Donner, Nicolino Ambrosino, Roger S. Goldstein, Pulmonary Rehabilitation, 2020
Luis Puente-Maestu, François Maltais, André Nyberg, Didier Saey
Striated muscles are contractile elements that feature repeating functional units called sarcomeres. Sarcomeres manifest as a series of bands visible along the muscle fibres, which give it its striated appearance in microscopic images. All striated muscles are attached to some component of the skeleton, allowing the mobilization of different structures of the body, and thus they are generally referred to as skeletal muscles. The muscles of the limbs are involved in ambulation and handling of objects, being essential for autonomy and the of the individual's quality of life. From the point of view of pulmonology, these muscles are generally referred to as ‘peripheral’. A set of thoracic muscles, whose function is to change intrathoracic pressures to allow ventilation, are called ventilatory or respiratory muscles. A number of pharyngeal, tongue, upper-limb, abdominal and cervical muscles are also involved in ventilation in different circumstances; however, they are not typically referred as respiratory muscles when considering skeletal muscle dysfunction in respiratory diseases.
Current status and advances in esophageal drug delivery technology: influence of physiological, pathophysiological and pharmaceutical factors
Published in Drug Delivery, 2023
Ai Wei Lim, Nicholas J. Talley, Marjorie M. Walker, Gert Storm, Susan Hua
The average thickness of the esophageal wall is approximately 1.87 to 2.70 mm in the dilated state and 4.05 to 5.68 mm in the contracted state (Xia et al., 2009). The thickness of the esophageal wall has also been reported to be slightly larger in males (5.26 mm) compared to females (4.34 mm) (Xia et al., 2009). The wall of the esophagus is comprised of the mucosa, submucosa, and muscularis propria (Figure 1). In healthy individuals, the mucosa is composed of three layers – non-keratinized, stratified squamous epithelium; lamina propria (composed of connective tissue); and muscularis mucosa (Scott-Brown et al., 2008; Orlando, 2010; Standring, 2020). The muscularis mucosa is composed primarily of smooth muscle, with a combination of striated muscles at the upper part of the esophagus. The submucosa layer consists of predominantly blood vessels, lymphatic vessels, minor salivary glands, connective tissues, and autonomic nerve plexus (i.e. submucosal plexus). The muscularis propria is formed by a mixture of striated and smooth muscles and is responsible for motor functions of the esophagus.
Study on circumpelvic muscle deformation and dynamic simulation of pelvic fracture reduction
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Jingtao Lei, Yanan Li, Haifei Xu
The soft tissue biomechanical model has been studied by some scholars. Wang and Hu (2011) applied Yeoh-type hyperelastic constitutive model to analyze the quasi-static mechanical properties of muscle soft tissue for pig hind leg muscles. A rate-dependent constitutive model was proposed to describe both the dynamic compression and tensile performance of pig hind leg muscles based on the experimental results. Paetsch et al. (2012) examined the transition of striated muscles between active and passive states. A strain energy function was formulated using the theory of transient networks, introducing an intermediate, stress-free configuration for the active muscle fibers. Additionally, energy dissipation occurring during the unloading is accounted for by specifying a pseudo-energy function. Wang (2014) selected Mooney-Rivlin hyperelastic model as muscle material. The geometric model of muscle was established by using reverse modeling software, and the finite element method was used to analyze the muscle stretch, and the validity of the biomechanical model was verified. Wang and Hu (2017) adopted Yeoh-type hyperelastic constitutive model to describe quasi-static mechanics performance of pig liver tissue. Based on visco-hyperelastic theory, a rate-dependent constitutive model was proposed to describe the mechanical properties of liver tissue from low strain rate to high strain rate, which was verified to be in good agreement with experimental results.
Circadian regulation of cardiac muscle function and protein degradation
Published in Chronobiology International, 2023
Proteostasis, including protein synthesis, processing/folding and degradation, is an important cellular mechanism in cardiac muscles (Henning and Brundel 2017; McLendon and Robbins 2015). Compared with non-muscle cells, cardiac muscles are terminally differentiated, must contract throughout lifetime, require robust metabolic/stress responses and involve specialized cellular machineries for electric conductance. The structural and functional unit of striated muscles, including both cardiac and skeletal muscles, is the sarcomere (Martin and Kirk 2020; Ono 2010), which is highly conserved throughout from worms to mammals. Sarcomeres line up sequentially, and tied together by a complex protein assembly called Z-disc to form contractible myofibrils, which in turn are bound in bundles to form cardiomyocytes. The sarcomere consists mainly of the myosin thick filaments and actin thin filaments, with a large number of associated structural and regulatory proteins. Given the heart is the first organ to be formed after birth and must continuously function until death, and that cardiomyocytes are post-mitotic, protein quality control at the sarcomere plays a particularly important role in cardiac proteostasis (Henning and Brundel 2017; Martin and Kirk 2020). Of particular importance is protein degradation mechanisms to remove misfolded or faulty proteins.