Stress distribution in the layered wall of the rat oesophagus

Liao, Donghua; Fan, Yanhua; Zeng, Yanjun; Gregersen, Hans

doi:10.1016/s1350-4533(03)00122-x

Cited by 59 publications

(66 citation statements)

References 17 publications

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“…Studies done with esophageal muscle from animals have shown that, when axial slices of passive esophageal muscle are cut along its circumference, it tends to open (16,29,33). The "opening angle" is a qualitative measure of "residual tension," the level of circularly oriented passive tension that would be required to reclose the gut segment and return muscle to its precut state.…”

Section: Discussionmentioning

confidence: 99%

“…We use, instead, the full equations within finite deformation theory (34). Furthermore, we include both circular and longitudinal muscle fibers in our modeled muscularis; in the fully passive state (tLESR), retaining this fiber anisotropy is important to capture correctly the variable muscle properties across the mucosa and muscle layers (29,30,33). In contrast with the muscularis, the mucosal layer is very compliant and provides little resistance to deformation compared with the much higher stiffness of the circular and longitudinal muscle layers (19,55).…”

Section: The Physio-mechanical Modelmentioning

confidence: 99%

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Liquid in the gastroesophageal segment promotes reflux, but compliance does not: a mathematical modeling study

Ghosh¹,

Kahrilas

Brasseur³

2008

American Journal of Physiology-Gastrointestinal and Liver Physi

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Ghosh SK, Kahrilas PJ, Brasseur JG. Liquid in the gastroesophageal segment promotes reflux, but compliance does not: a mathematical modeling study. Am J Physiol Gastrointest Liver Physiol 295: G920 -G933, 2008. First published August 21, 2008 doi:10.1152/ajpgi.90310.2008.-The mechanical force relationships that distinguish normal from chronic reflux at sphincter opening are poorly understood and difficult to measure in vivo. Our aim was to apply physics-based computer simulations to determine mechanical pathogenesis of gastroesophageal reflux. A mathematical model of the gastroesophageal segment (GES) was developed, incorporating the primary anatomical and physiomechanical elements that drive GES opening and reflux. In vivo data were used to quantify muscle stiffness, sphincter tone, and gastric pressure. The liquid lining the mucosa was modeled as an "effective liquid film" between the mucosa and a manometric catheter. Newton's second law was solved mathematically, and the space-time details of opening and reflux were predicted for systematic variations in gastric pressure increase, film thickness, muscle stiffness, and tone. "Reflux" was defined as "2 ml of refluxate entering the esophagus within 1 s." GES opening and reflux were different events. Both were sensitive to changes in gastric pressure and sphincter tone. Reflux initiation was extremely sensitive to the liquid film thickness; the protective function of the sphincter was destroyed with only 0.4 mm of liquid in the GES. Compliance had no effect on reflux initiation, but affected reflux volume. The presence of abnormal levels of liquid within the collapsed GES can greatly increase the probability for reflux, suggesting a mechanical mechanism that may differentiate normal reflux from gastroesophageal reflux disease. Compliance does not affect the probability for reflux, but affects reflux volume once it occurs. Opening without reflux suggests the existence of "gastroesophageal pooling" in the distal esophagus, with clinical implications. gastroesophageal reflux disease; lower esophageal sphincter; compliance; stiffness MUCH IS UNDERSTOOD ABOUT THE biomechanics underlying gastroesophageal reflux once refluxate flow into the esophagus has occurred, such as sphincter relaxation pressures (21), transsphincteric pressure gradient (46), hiatal distension (25), and the proximal extent of reflux (11). However, the mechanical differences that distinguish normal from chronic reflux are those that manifest at the time of opening and the initiation of reflux; these are less well understood. This lack of understanding of the initiation process is primarily because the initial opening process involves a level of mechanical subtlety in the balances among multiple forces and muscle deformations that are difficult to measure accurately in vivo due to rapid changes occurring over very short times with small changes in radial distention.The opening of the gastroesophageal segment (GES) and reflux result from dynamic adjustments in the subtle force balance that are initi...

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Section: Discussionmentioning

confidence: 99%

Section: The Physio-mechanical Modelmentioning

confidence: 99%

Liquid in the gastroesophageal segment promotes reflux, but compliance does not: a mathematical modeling study

Ghosh¹,

Kahrilas

Brasseur³

2008

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…The most current investigations of the GI tissue properties are mainly focused on seeking the constitutive equation and the associated constitutive parameters of the physiological or pathological status (Gregersen 2002;Liao et al 2003;Zhao et al 2003Zhao et al , 2007Yang et al 2004Yang et al , 2006Lu et al 2005). Most GI structure and tissue property studies have been based on animal experiments so far.…”

Section: (A ) Mechanical Properties Of the Gi Tissuesmentioning

confidence: 99%

Biomechanical functional and sensory modelling of the gastrointestinal tract

Liao

Lelic

Gao

et al. 2008

Phil. Trans. R. Soc. A.

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The aim of this review is to describe the biomechanical, functional and sensory modelling work that can be used to integrate the physiological, anatomical and medical knowledge of the gastrointestinal (GI ) system. The computational modelling in the GI tract was designed, implemented and evaluated using a series of information and communication technologies-based tools. These tools modelled the morphometry, biomechanics, functions and sensory aspects of the human GI tract. The research presented in this review is based on the virtual physiological human concept that pursues a holistic approach to representation of the human body. Such computational modelling combines imaging data, GI physiology, the gut-brain axis, geometrical and biomechanical reconstruction, and computer graphics for mechanical, electronic and pain analysis. The developed modelling will aid research and ensure that medical professionals benefit through the provision of relevant and precise information about a patient's condition. It will also improve the accuracy and efficiency of the medical procedures that could result in reduced cost for diagnosis and treatment.

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“…The angle subtended by the open ring, referred to as the opening angle, is used as a measure of the residual stress present in the intact ring of the tissue [2] . However, recent studies on multi-layered organs such as blood vessels and the GI tract indicate that the zero-stress state differs between layers and that a stress jump exists between the layers [5][6][7][8][9][10][11] . Thus, the true stressfree configuration for a multi-layered model is at least a twice cut tissue ring; one circumferential cut for layer separation and one radial cut in each layer to generate a true stress-free state.…”

mentioning

confidence: 99%

“…In yet unpublished studies, the zero-stress morphology data were obtained from five male 300 g Wistar rats. Geometric models for the oesophageal muscle and mucosal-submucosal layer were generated based on the morphology of the separated oesophagus at the zero-stress state [5,6,15] . The oesophageal passive mechanical properties were tested from the two other Wistar rats by using a tensile test machine [16,17] .…”

mentioning

confidence: 99%

The oesophageal zero-stress state and mucosal folding from a GIOME perspective

Liao

Zhao²,

Yang³

et al. 2007

WJG

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The oesophagus is a cylindrical organ with a collapsed lumen and mucosal folds. The mucosal folding may serve to advance the function of the oesophagus, i.e. the folds have a major influence on the flow of air and bolus through the oesophagus. Experimental studies have demonstrated oesophageal mucosal folds in the noload state. This indicates that mucosal buckling must be considered in the analysis of the mechanical reference state since the material stiffness drops dramatically after tissue collapse. Most previous work on the oesophageal zero-stress state and mucosal folding has been experimental. However, numerical analysis offers a promising alternative approach, with the additional ability to predict the mucosal buckling behaviour and to calculate the regional stress and strain in complex structures. A numerical model used for describing the mechanical behaviour of the mucosal-folded, threelayered, two-dimensional oesophageal model is reviewed. GIOME models can be used in the future to predict the tissue function physiologically and pathologically. EXPERIMENTAL AND MODELING APPROACHES TO THE ZERO-STRESS STATE AND MUCOSAL BUCKLINGNew computational models for describing the gastrointestinal (GI) tract mechanical behaviour precisely are a GIOME approach for bioengineering tissue modelling. The zero-stress state provides a standardized reference state for describing the mechanical response to external loading [1][2][3][4] . A large number of studies have been published on the zero-stress state of the cardiovascular and GI systems. The zero-stress state in soft biological tissues can be obtained by an experiment where tissue rings are cut radically, opening up into sectors. The angle subtended by the open ring, referred to as the opening angle, is used as a measure of the residual stress present in the intact ring of the tissue [2] . However, recent studies on multi-layered organs such as blood vessels and the GI tract indicate that the zero-stress state differs between layers and that a stress jump exists between the layers [5][6][7][8][9][10][11] . Thus, the true stressfree configuration for a multi-layered model is at least a twice cut tissue ring; one circumferential cut for layer separation and one radial cut in each layer to generate a true stress-free state.Longitudinal mucosal folds exist throughout the length of the oesophagus. It was originally believed that the folding was caused by the contraction of the muscle layer in an in vivo state [12] . However, the folds appear even at the no-load state [5] . Hence, additional tension caused by the compressed mucosa-submucosal layer exists in the muscle layer at the no-load state. Furthermore, the mucosal layer is not perfectly elastic, its circumferential length cannot decrease to zero, thus the tension in the muscle layer will collapse the mucosal layer [12] . Therefore, the buckling feature of the oesophagus must be accounted for in a reference state analysis since the material stiffness drops dramatically after tissue collapse.In the airways it ha...

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Stress distribution in the layered wall of the rat oesophagus

Cited by 59 publications

References 17 publications

Liquid in the gastroesophageal segment promotes reflux, but compliance does not: a mathematical modeling study

Liquid in the gastroesophageal segment promotes reflux, but compliance does not: a mathematical modeling study

Biomechanical functional and sensory modelling of the gastrointestinal tract

The oesophageal zero-stress state and mucosal folding from a GIOME perspective

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