Anococcygeal Raphe Revisited: A Histological Study Using Mid-Term Human Fetuses and Elderly Cadavers

Kinugasa, Yusuke; Arakawa, Takeo; Abé, Hiroshi; Abe, Shinichi; Cho, Baik Hwan; Murakami, Gen; Sugihara, Kenichi

doi:10.3349/ymj.2012.53.4.849

Cited by 19 publications

(14 citation statements)

References 25 publications

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“…Hence, we suspect that lower FA values in the PB region likely represent crossing of muscle fibers from one side to the other. FA values in the anococcygeal raphe are similar to those in the right and left EAS, implying the existence of muscle fibers (tensor behavior of water diffusion) in the anococcygeal raphe, a finding similar to a recent histological study (15) and contrary to the conventional thinking that the anococcygeal raphe is a fibroaponeurotic structure.…”

Section: Discussionsupporting

confidence: 49%

Purse-string morphology of external anal sphincter revealed by novel imaging techniques

Mittal

Bhargava

Sheean

et al. 2014

American Journal of Physiology-Gastrointestinal and Liver Physi

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Mittal RK, Bhargava V, Sheean G, Ledgerwood M, Sinha S. Purse-string morphology of external anal sphincter revealed by novel imaging techniques. Am J Physiol Gastrointest Liver Physiol 306: G505-G514, 2014. First published January 23, 2014 doi:10.1152/ajpgi.00338.2013.-The external anal sphincter (EAS) may be injured in 25-35% of women during the first and subsequent vaginal childbirths and is likely the most common cause of anal incontinence. Since its first description almost 300 years ago, the EAS was believed to be a circular or a "donut-shaped" structure. Using three-dimensional transperineal ultrasound imaging, MRI, diffusion tensor imaging, and muscle fiber tracking, we delineated various components of the EAS and their muscle fiber directions. These novel imaging techniques suggest "purse-string" morphology, with "EAS muscles" crossing contralaterally in the perineal body to the contralateral transverse perineal (TP) and bulbospongiosus (BS) muscles, thus attaching the EAS to the pubic rami. Spin-tag MRI demonstrated purse-string action of the EAS muscle. Electromyography of TP/BS and EAS muscles revealed their simultaneous contraction and relaxation. Lidocaine injection into the TP/BS muscle significantly reduced anal canal pressure. These studies support purse-string morphology of the EAS to constrict/close the anal canal opening. Our findings have implications for the effect of episiotomy on anal closure function and the currently used surgical technique (overlapping sphincteroplasty) for EAS reconstructive surgery to treat anal incontinence. external anal sphincter muscle architecture; anal incontinence; childbirth-related injury; magnetic resonance diffusion tensor imaging AN UNDERSTANDING OF THE MORPHOLOGY of the external anal sphincter (EAS), one of the superficial muscles of the pelvic floor, is important, since damage to this muscle may occur in 25-35% of women during vaginal childbirth (34). Injury to the EAS muscle is an important cause of anal incontinence, which has a devastating effect on an individual's quality of life (8). Morphology of the EAS has intrigued many investigators. From the original description by Santorini at the turn of 18th century (27) to the most current texts (2, 19), the EAS is described as a three-component (subcutaneous, superficial, and deep) circular muscle structure (2, 19). Others have argued that the deep part of the EAS is actually the puborectalis muscle (PRM) (7,14,23,25). MRI studies of Hussain et al. (14) and our recent three-dimensional (3-D) ultrasound (US) images, combined with high-definition manometry maps (25), support the idea that the deep part of the EAS is indeed the PRM, because it has a "sling" shape. On the basis of 3-D US images and anal canal pressures obtained by high-definition manometry (HDM), our study shows that the increase in pressure with voluntary contraction of the proximal and distal halves of the anal canal is related to contraction of the PRM and EAS, respectively (25).Another aspect of EAS morphology that has never been questi...

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Section: Discussionsupporting

confidence: 49%

Purse-string morphology of external anal sphincter revealed by novel imaging techniques

Mittal

Bhargava

Sheean

et al. 2014

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…The bilayered appearance of the pubovisceral muscle is reminiscent of the multilayered architecture of the LAM in some dissections [ 6 , 18 , 19 ]. A further difference between our sectional and dissectional studies is that the area, in which we and others [ 1 ] identified the smooth rectococcygeal muscle, is described as the midline raphe of the LAM [ 24 ] or the anterior layer of the anococcygeal ligament [ 25 , 26 ].…”

Section: Discussionmentioning

confidence: 99%

3D Topography of the Young Adult Anal Sphincter Complex Reconstructed from Undeformed Serial Anatomical Sections

Dabhoiwala

Hagoort

et al. 2015

PLoS ONE

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BackgroundPelvic-floor anatomy is usually studied by artifact-prone dissection or imaging, which requires prior anatomical knowledge. We used the serial-section approach to settle contentious issues and an interactive 3D-pdf to make the results widely accessible.Method3D reconstructions of undeformed thin serial anatomical sections of 4 females and 2 males (21–35y) of the Chinese Visible Human database.FindingsBased on tendinous septa and muscle-fiber orientation as segmentation guides, the anal-sphincter complex (ASC) comprised the subcutaneous external anal sphincter (EAS) and the U-shaped puborectal muscle, a part of the levator ani muscle (LAM). The anococcygeal ligament fixed the EAS to the coccygeal bone. The puborectal-muscle loops, which define the levator hiatus, passed around the anorectal junction and inserted anteriorly on the perineal body and pubic bone. The LAM had a common anterior attachment to the pubic bone, but separated posteriorly into puborectal and “pubovisceral” muscles. This pubovisceral muscle was bilayered: its internal layer attached to the conjoint longitudinal muscle of the rectum and the rectococcygeal fascia, while its outer, patchy layer reinforced the inner layer. ASC contraction makes the ano-rectal bend more acute and lifts the pelvic floor. Extensions of the rectal longitudinal smooth muscle to the coccygeal bone (rectococcygeal muscle), perineal body (rectoperineal muscle), and endopelvic fascia (conjoint longitudinal and pubovisceral muscles) formed a “diaphragm” at the inferior boundary of the mesorectum that suspended the anorectal junction. Its contraction should straighten the anorectal bend.ConclusionThe serial-section approach settled contentious topographic issues of the pelvic floor. We propose that the ASC is involved in continence and the rectal diaphragm in defecation.

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“…In accordance with Bayliss' rule, rather than traction or elevation, the PSMs seem to act as an ideal barrier, septum or protector against mechanical stress such as that resulting from intra-abdominal pressure. In addition, Petros's "posterior levator plate" (the anococcygeal ligament and raphe) is elastic [55,67] and unlikely to provide any strong posterior traction force. Another review [68] has focused on the limited effect of the levator ani on urethral function in both genders.…”

Section: Open Accessmentioning

confidence: 99%

Supportive tissues of the vagina with special reference to a fibrous skeleton in the perineum: A review

Sasaki¹,

Hinata²,

Kurokawa³

et al. 2014

OJOG

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With the aid of immunohistochemistry, the present review attempts to demonstrate the composite fibers and nerve topographical anatomy in the vaginal supportive tissues. Along the tendinous arch of the pelvic fasciae, distal parts of the pelvic plexus extend antero-inferiorly and issue nerves to the internal anal sphincter as well as the cavernous tissues. At the attachment of the levator ani muscle to the rectum, smooth muscles in the endopelvic fascia lining the levator ani merge with the longitudinal smooth muscle layer of the rectum to provide the conjoint longitudinal muscle coat or the longitudinal anal muscle (LAM: smooth muscle). However, at the rectovaginal interface, the longitudinal smooth muscle layer of the rectum continues to the LAM without any contribution of the endopelvic fascia. The bilateral masses of the perineal smooth muscles (PSMs) are connected by the perineal body, and the PSMs receive 1) the longitudinal anal muscle, 2) the internal and external anal sphincters and, 3) the perineal membrane lining the vestibular wall. Tensile stress from the levator ani seems to be transferred to the PSMs via the LAM. Because of their irregularly arrayed muscle fibers, instead of a synchronized contraction in response to nerve impulses, the PSMs are likely to act as a barrier, septum or protector against mechanical stress because, even without innervation, such smooth muscle fibers resist (not absorb) pressure, in accordance with Bayliss' rule. The external anal sphincter, a strong striated muscle, inserts into the PSMs and seems to play a dynamic role in supporting the rectovaginal interface to maintain the antero-posterior length of the urogenital hiatus. However, we do not think that smooth muscles play an active traction role without cooperation from striated muscle. The fibrous skeleton composed of smooth muscle in the female perineum is explained in terms of a "catamaran" model.

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Anococcygeal Raphe Revisited: A Histological Study Using Mid-Term Human Fetuses and Elderly Cadavers

Cited by 19 publications

References 25 publications

Purse-string morphology of external anal sphincter revealed by novel imaging techniques

Purse-string morphology of external anal sphincter revealed by novel imaging techniques

3D Topography of the Young Adult Anal Sphincter Complex Reconstructed from Undeformed Serial Anatomical Sections

Supportive tissues of the vagina with special reference to a fibrous skeleton in the perineum: A review

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