NDLI: Length-tension relationship of the external anal sphincter muscle: implications for the anal canal function.

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Rajasekaran, Mahadevan Raj Jiang, Yanfen Bhargava, Valmik Littlefield, Ryan Lee, Andrew Lieber, Richard L. Mittal, Ravinder K.
Description	Country affiliation: United States Author Affiliation: Rajasekaran MR ( Department of Medicine, Division of Gastroenterology, University of California, San Diego and San Diego Veterans Affairs Healthcare System, San Diego, California 92161, USA.)
Abstract	The length at which a muscle operates in vivo (operational length) and the length at which it generates maximal force (optimal length) may be quite different. We studied active and passive length-tension characteristics of external anal sphincter (EAS) in vivo and in vitro to determine the optimal and operational length of rabbit EAS. For the in vitro studies, rings of EAS (n = 4) were prepared and studied in a muscle bath under isometric conditions. For in vivo studies, female rabbits (n = 19) were anesthetized and anal canal pressure was recorded by use of a sleeve sensor placed in the custom-designed catheter holders of 4.5-, 6-, and 9-mm diameters. Measurements were obtained at rest and during EAS electrical stimulation. Sarcomere length of EAS muscle was measured by laser diffraction technique with no probe and three probes in the anal canal. In vitro studies revealed 2,054 mN/cm(2) active tension at optimal length. In vivo studies revealed a probe size-dependent increase in anal canal pressure and tension. Maximal increase in anal canal tension with stimulation was recorded with the 9-mm probe. Increases in anal canal tension with increase in probe size were completely abolished by pancuronium bromide. EAS muscle sarcomere length without and with 9-mm probe in the anal canal were 2.11 +/- 0.08 and 2.99 +/- 0.07 microm, respectively. Optimal sarcomere length, based on the thin filament length measured by thin filament analysis, is 2.44 +/- 0.10 microm. These data show that the operational length of EAS is significantly shorter than its optimal length. Our findings provide insight into EAS function and we propose the possibility of increasing anal canal pressure by surgical manipulation of the EAS sarcomere length.
File Format	HTM / HTML
ISSN	01931857
e-ISSN	15221547
DOI	10.1152/ajpgi.00033.2008
Journal	AJP: Gastrointestinal and Liver Physiology
Issue Number	2
Volume Number	295
Language	English
Publisher	American Physiological Society
Publisher Date	2008-08-01
Publisher Place	United States
Access Restriction	Open
Subject Keyword	Discipline Physiology Discipline Gastroenterology Anal Canal Physiology Anatomy & Histology Animals Electric Stimulation Muscle Contraction Drug Effects Nitroprusside Pharmacology Pancuronium Rabbits Research Support, N.i.h., Extramural
Content Type	Text
Resource Type	Article
Subject	Hepatology Physiology Physiology (medical) Gastroenterology

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Length-tension relationship of the external anal sphincter muscle: implications for the anal canal function

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Length-tension relationship of the external anal sphincter muscle: implications for the anal canal function

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