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Circular smooth muscle contributes to esophageal shortening during peristalsis

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We found that 1 the shortening of the circular smooth muscle CSM and longitudinal smooth muscle LSMat 5 cm was significantly greater than at 20 cm above the distal esophageal high pressure zone; and 2 the CSM and LSM both shortened in the longitudinal direction but the CSM contribution towards longitudinal esophageal shortening at the distal esophagus was greater than at the proximal esophagus[ 12 ]. This was surprising, as it was commonly assumed that the LSM of the esophagus was completely responsible for esophageal shortening, while the CSM was responsible for the narrowing of the lumen and the pressure generated within the esophageal lumen.

Before this finding it was assumed that CSM contraction did not actively contribute to the longitudinal esophageal shortening and that any shortening within the CSM occurred by longitudinal smooth muscle drag. We proposed several hypotheses to explain this physiologic phenomenon: This also cannot explain the regional differences in shortening along the length of the esophagus; 2 the entire esophagus is tonically stretched at rest under axial tension and during swallowing there is a decrease in this tension due to deglutitive inhibition causing the circular smooth muscle to shorten, as a spring would shorten when the tension was released.

Once again this could account for some of the CSM shortening but could not account for the differences in CSM shortening along the length of the esophagus; and 3 the CSM fibers actually spiral down the esophagus at an angle other than perpendicular to the longitudinal axis leading to subsequent shortening of the CSM during peristaltic contraction.

This seemed the most likely explanation for the CSM shortening more than that contributed by LSM in the distal esophagus. In addition we hypothesized that if this was the case, one would observe that the distal spiral angle would be greater than the proximal spiral angle. The aim of this study was to provide an explanation to the functional observation obtained by Dai et al[ 12 ], that the CSM shortens more than can be explained by longitudinal drag of the LSM alone during peristaltic contraction, especially in the distal esophagus.

Data management, analysis and interpretation and preparation of the manuscript were performed by the authors who had full access to all the study data. All authors had responsibility for the decision to submit the manuscript for publication, and vouch for the accuracy, integrity, and completeness of the data as reported. Assessments and outcome measurements In the current study, we used fine dissection of cadaveric esophagi to define the LSM and CSM layers in detail. Angles of the CSM fibers relative to the axial direction longitudinal muscle fibers of the esophagus were measured.

In addition, we used micro-computed tomography micro CT scan to virtually dissect the human esophagi obtained from organ transplant donors to evaluate the angle of the CSM relative to LSM. Cadaveric esophageal measurements Nine human esophagi were procured from formaldehyde preserved cadavers previously used for medical education purposes. Each esophagus was removed from the pharnygo-esophageal junction to the cardia of the stomach.

The outer longitudinal layer of the muscularis propria was exposed after carefully stripping the outer serosa.

Minimal tension was applied to straighten the esophagus and the esophagus was then longitudinally cut open in a straight line following the orientation of the longitudinal muscles.

The squamocolumnar junction SCJ was identified on the mucosa and its location was marked on the specimen.

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The inner circular layer of the muscularis propria was then revealed after careful dissection of the esophageal mucosa and the underlying muscularis mucosa. Although the entire esophagus is much longer only the distal 10 cm of the esophagus was used to make measurements. A ruler was also included in the pictures with a mark placed at the SCJ, which was identified earlier. The ruler was also used to mark the esophagus at every centimeter proximal to the SCJ. Special attention was given to ensure that the folded-back longitudinal layer was in its in vivo position relative to the circular layer by carefully aligning the marks made along the incision line on the esophagus before it was cut open Figure 1.

The esophagus is cut longitudinally along the longitudinal muscle fibers after dissecting the serosa. The mucosa and sub mucosa were later dissected.

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The esophagus was later folded back so that the longitudinal fibers were on top of the circular muscle fibers. Measurements of the angle of the circular smooth muscle fibers with respect to the longitudinal smooth muscle fibers were made starting from the squamocolumnar junction.

Image Pro Plus version 6. MD was used to analyze each digital image. Angles between the longitudinal and the circular muscles were measured by two independent investigators, blinded to the other investigators measurements. Measurements were made starting at the SCJ and moving proximally measuring every 1 cm for 10 cm.

High-resolution micro-computed tomography scan of the gastroesophageal junction Two human esophagi and stomachs were obtained from organ transplant donors National Disease Research Institute and the International Institute for the Advancement of Medicine.

This block of tissue was supported by a piece of Styrofoam that was shaped to match the shape of the specimen and wrapped in Parafilm and sealed closed to maintain hydration.

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SkyScan high-resolution cone-beam micro-CT scanner SkyScan, Ltd, Kontich, Belgiumwith a Hamamatsu C 11Mp camera, was used to scan the specimens using the double-size and oversize sample options.

The following settings were used: The image slices were reconstructed using cone-beam reconstruction software SkyScan NRecon based on the Feldkamp algorithm, on 3 linked servers, a process that yielded tomographic sections, each with a thickness of Although the entire esophagus is much longer only the distal 5 cm of the esophagus was used due to the limitations of the micro-CT scanner.

The longitudinal muscle fibers were virtually dissected to expose the underlying circular muscle fibers. Measurements were made starting from the squamocolumnar junction. Statistical analysis was performed using one way analysis of variance with post hoc pair wise comparisons using the Bonferroni method.

The x-axis represents the distance from the squamocolumnar junction with 0 being the squamocolumnar junction. At 90 degrees the circular smooth muscle and longitudinal smooth muscle are perpendicular to each other. Therefore the smaller the angle the greater the deviation from the perpendicular and the greater the resulting shortening during peristaltic contraction; B: Measured using micro computed tomography.

Dodds et al[ 6 ] measured the axial motion of four tantalum wires inserted into the cat esophageal mucosa in vivo. The micrographs show presence of a large number of pores in different sizes On the other hand, Figure 4 shows presence of Nano structures which ranging from 35 nm to 95 nm. The peak at about 5.

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The peak at about 4. The prepared copolymer AcAc-AcAm hydrogels contain amine and carboxylate groups in their interpenetrated networks. We investigated the effect of pH on the swelling behavior of the Copolymer AAc-AcAm hydrogels by using buffer solutions with pH values of 1. In addition, since Cl- ions that can freely move exist in the solution, and the Donnan osmotic pressure based on the Donnan effect between free ion Cl- ion and fixed ion cationic amine group in AcAm occurs, the water content of hydrogel increased.

Donnan effect is greatly dependent on ionic strength of the external solution. As a result, the hydrogel shows increase of water content due to repulsion by electrostatic interaction and swelling by the Donnan osmotic pressure as the hydrogel has the cationic charge. The release study carried out at pH 1. Figures 10 and 11 showed the results of release studies.

Journal of Controlled Release A swelling study in surfactant and polymer solutions. Reactive and Functional Polymers Physical Review Letters Nature Reviews Drug Discovery 3: Molecular Aspects of Medicine