Anatomy of the external anal sphincter in man

The anatomy of the external anal sphincter was studied in 20 adult human cadavers of both sexes by dissection and histological examination. The external anal sphincter is not naturally divided into layers or laminae. The lowermost muscle bundles differ from the main part in being completely surrounded by thick fibrous tissue septa derived form the longitudinal anal coat. The perineal branch of S4 supplies the posterior third, the inferior haemorrhoidal nerves supply the anterior two thirds. All fibres of the sphincter retain their skeletal attachment to the anococcygeal ligament to the coccyx. Some fibres cross the median plane to be continuous with the transversus perinei of the opposite side. A cleft was displayed separating the lower border of the levator ani muscle from the upper border of the external anal sphincter. The muscle bundles of the sphincter are arranged circumferentially in one continuous circle and not in loops. Fibres from the anterior border of the levator ani muscle extend to cover and blend with the outer surface of the external sphincter in their way to the anococcygeal ligament.     

基于经会阴实时三维超声评估生物反馈电刺激联合盆底肌锻炼治疗产后盆底功能障碍的临床疗效

摘要 目的：探讨经会阴实时三维超声评估生物反馈电刺激联合盆底肌锻炼治疗产后盆底功能障碍的临床疗效。方法：选择2020年9月至2022年9月我院收治的96例产后盆底功能障碍患者,根据随机数字表法将患者分为两组,对照组（48例）采用盆底肌锻炼治疗,研究组（48例）采用生物反馈电刺激联合盆底肌锻炼治疗。治疗前后采用经会阴实时三维超声检查,对比两组治疗前后的盆底功能障碍调查表（PFDI-20）、盆底障碍影响简易问卷7（PFIQ-7）评分、静息和Valsalva动作状态下的肛提肌超声参数。分析肛提肌超声参数与PFDI-20、PFIQ-7评分的相关性。结果：两组治疗后PFDI-20、PFIQ-7评分,静息和Valsalva动作状态下肛提肌裂孔前后径、肛提肌裂孔左右径、肛提肌裂孔面积较治疗前降低（P＜0.05）,静息时肛提肌厚度较治疗前增加（P＜0.05）。研究组治疗后PFDI-20、PFIQ-7评分,静息和Valsalva动作状态下肛提肌裂孔前后径、肛提肌裂孔左右径、肛提肌裂孔面积低于对照组（P＜0.05）,静息时肛提肌厚度大于对照组（P＜0.05）。静息和Valsalva状态下肛提肌裂孔前后径、肛提肌裂孔左右径、肛提肌裂孔面积与PFDI-20、PFIQ-7评分呈正相关（P＜0.05）,静息状态肛提肌厚度与PFDI-20、PFIQ-7评分呈负相关（P＜0.05）。结论：经生物反馈电刺激联合盆底肌锻炼治疗后肛提肌裂孔大小较治疗前降低,肛提肌厚度较治疗前增加,且与PFDI-20、PFIQ-7评分改善有关,经会阴实时三维超声可客观、有效评价产后盆底功能障碍患者的治疗效果。     

Function of the anal sphincters following anterior resections of rectum

The purpose of the present work is to evaluate the function of the anal sphincter following anterior resections of the rectum. Our data have shown that the anorectal reflex did not depend on the presence of the rectal mucosa. The external anal sphincter contraction involves a reflex which is initiated by stretch receptors in the levator ani muscle. The internal anal sphincter relaxation is likely a local reflex involving nerve pathways not yet completely defined.     

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

Background

Pelvic-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.

Method

3D reconstructions of undeformed thin serial anatomical sections of 4 females and 2 males (21–35y) of the Chinese Visible Human database.

Findings

Based 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.

Conclusion

The 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.     

Coccygeus and levator ani muscles in the rabbit: morphology and proprioceptive innervation

The Authors have studied the morphological features and the proprioceptive nervous component in the coccygeus and levator ani muscles of the rabbit, using Ruffini's and Barker-Ip's impregnations. The coccygeus muscle originates from ischiatic spine and inserts on the last three sacral vertebrae and on the first four or five caudal vertebrae. The levator ani muscle originates from the ischiatic spine and the coccygeus muscle aponeurosis and inserts directly on the caudal vertebrae 3-5 or 4-6. The proprioceptive innervation in both muscles is constituted by muscle spindles and Golgi tendon organs with a typical structure. Muscle spindles are more numerous than Golgi tendon organs and the spindle density is higher in the levator ani muscle.     

Electrophysiological experiments on the mechanism and accuracy of neuromuscular specificity in the axolotl.

The supracoracoideus muscle of the axolotl shoulder girdle is innervated by two nerves, the supracoracoideus nerve (SC) supplying most of the muscle and the posterior supracoracoideus (PSC) supplying the posterior corner. All the muscle fibres are multiply innervated and at the border between the two innervations many muscle fibres, when penetrated by a microelectrode, show junction potentials from both nerves. In such cases one junction potential is often very small, below the threshold for exciting muscle contraction, the other large and effective at exciting the muscle. If the SC nerve is cut, the territory of the PSC nerve expands over several weeks. Upon regrowth of the cut nerve it reinnervates its old muscle fibres and removes the previous foreign innervation, the borderline between the two nerve territories being established exactly as before. This depends upon two processes, sprouting of nerves and a competitive repression of transmission from nerves ending on foreign muscle fibres.     

Subject specific finite elasticity simulations of the pelvic floor

An anatomically realistic computational model of the pelvic floor and anal canal regions was used in this study to examine the mechanics of normal defecatory function within the female pelvic floor. This subject specific, MRI-based model enabled mechanical simulations to be performed and quantitatively assessed against experimental data retrieved from the same volunteer. The levator ani muscle group mesh was used as the domain over which the governing equations of finite elasticity were solved using the finite element method with a Mooney-Rivlin material law. Deformation of the levator ani was simulated during a 'bear down' maneuver in order to visualize the way this muscle group functions in an asymptomatic subject. A pressure of 4 kPa was imposed on the mesh and the computed mesh displacements were compared to those obtained from dynamic MR images with an average, experimentally consistent, downwards displacement of 27.2 mm being achieved. The RMS error for this movement was 0.7 mm equating to a percentage error of 2.6% in the supero-inferior direction and 13.7 mm or 74.5% in the antero-posterior direction.     

三维超声技术对于评估压力性尿失禁女性患者盆底肌肉收缩及膀胱颈活动度的价值研究

摘要 目的：探讨三维超声技术对于评估压力性尿失禁（SUI）女性患者盆底肌肉收缩及膀胱颈活动度的价值。方法：选取2020年1月至2021年8月本院的收治的因产后SUI的女性患者60例作为观察组,另选择同期产后正常的女性受试者60例作为对照组,所有受试者均行经会阴三维超声检查。比较两组之间盆底肌肉收缩及膀胱颈活动度等相关指标的差异。结果：在静息状态和最大Valsalva状态下,观察组中盆膈裂孔前后径、左右径、肛提肌裂孔面积以及膀胱颈后角均显著大于对照组（P<0.05）,观察组尿道长度显著低于对照组（P<0.05）;而仅在最大Valsalva状态下,观察组的膀胱颈位置显著低于对照组（P<0.05）;此外观察组膀胱漏斗化所占比例显著高于对照组（P<0.05）。结论：三维超声技术可以清晰直观地显示女性盆底组织结构和功能,对于评估SUI女性患者盆底肌肉收缩及膀胱颈活动度具有一定的诊断价值,并为临床提供真实客观的影像学证据。     

Histochemical studies on the amphibian opercularis muscle (Amphibia)

Summary Histochemical studies of the opercularis muscle of the bullfrog (Rana catesbeiana) and the tiger salamander (Ambystoma tigrinum) provide evidence that the opercularis muscle of anurans is a specialized, tonic portion of the levator scapulae superior muscle. Staining results for myosin adenosine triphosphatase (ATPase) and succinate dehydrogenase (SDH), combined with measurements of muscle fiber diameters, demonstrate that the opercularis/levator scapulae superior muscle mass of both the tiger salamander and bullfrog consists of an anterior tonic portion, a middle fast oxidative-glycolytic (FOG) twitch portion, and a posterior fast-glycolytic (FG) twitch portion. In R. catesbeiana the tonic fibers represent 57.3% of the fiber total and (because they have relatively narrow diameters) about 29% of the cross-sectional area of the muscle mass, and form that part of the muscle (=opercularis muscle) that inserts on the operculum. In Ambystoma the tonic fibers represent only 8.8% of the fiber total and represent about 4% of the cross-sectional area. In the tiger salamander, the entire levator scapulae superior muscle inserts on the operculum and therefore represents the opercularis muscle. The bullfrog differs from the tiger salamander, therefore, in that the anterior tonic part of the opercularis/levator scapulae superior complex is greatly enlarged and the insertion on the operculum is limited to these tonic fibers. No evidence of a columellar muscle was found in R. catesbeiana. Previous reports of one in this species and in other anurans may be based on the tripartite nature of the opercularis/levator scapulae superior muscle mass. The middle FOG portion of the muscle may have been considered a muscle distinct from the anterior tonic portion (=opercularis muscle) and the posterior FG portion.     

Effects of nonlinear muscle elasticity on pelvic floor mechanics during vaginal childbirth

The role of the pelvic floor soft tissues during the second stage of labor, particularly the levator ani muscle, has attracted much interest recently. It has been postulated that the passage of the fetal head through the pelvis may cause excessive stretching of the levator ani muscle, which may lead to pelvic floor dysfunction and pelvic organ prolapse later in life. In order to study the complex biomechanical interactions between the levator ani muscle and the fetal head during the second stage of labor, finite element models have been developed for quantitative analysis of this process. In this study we have simulated vaginal delivery using individual-specific anatomical computer models of the pelvic floor interacting with a fetal head model with minimal restrictions placed upon its motion. Two constitutive relations were considered for the levator ani muscle (of exponential and neo-Hookean forms). For comparison purposes, the exponential relation was chosen to exhibit much greater stiffening at higher strains beyond the range of the experimental data. We demonstrated that increased nonlinearity in the elastic response of the tissues leads to considerably higher (56%) estimated force required for delivery, accompanied by a more homogeneous spatial distribution of maximum principal stretch ratio across the muscle. These results indicate that the form of constitutive relation beyond the presently available experimental data markedly affects the estimated function of the levator ani muscle during vaginal delivery, due to the large strains that occur. Further experimental data at higher strains are necessary in order to more reliably characterize the constitutive behavior required for modeling vaginal childbirth.     

Muscles of the pelvic outlet in the fowl (Gallus gallus domesticus) with special reference to their nerve supply.

The manner of innervation of the pelvic outlet muscles in fowl (Gallus gallus domesticus) was examined in detail in four male pelvic halves. The segmental arrangement of the nerve supply in the sacral and pudendal plexuses was compared to that of Lacertilia and Urodela as a basis for a morphological analysis of the pelvic outlet muscles. From the viewpoint of innervation, the pelvic outlet muscles of fowl are classified into two groups: a sphincter muscle group and a levator muscle group. These two groups are closely related to the ventral muscles of the pelvic limb. In contrast to the morphology of pelvic outlet muscles in lacertilians, in fowl the caudal muscle element does not contribute to the formation of these muscles.     

Histochemical and stereological analysis of the levator ani (pubocaudal) muscle in nulliparous and multiparous beagles

Fiber-type composition and several stereological parameters of the levator ani (pubocaudal) muscle were evaluated in five nulliparous and five multiparous beagles using myosin ATPase-histochemistry and systematically selected muscle cross-sections. With respect to the narrow canine pelvic cavity, this study was also undertaken to determine whether vaginal birth of at least seven litters causes similar neuromuscular changes in the canine levator ani (pubocaudal) muscle analoguous to those seen in the pelvic floor muscles of women after vaginal delivery. The canine pubocaudal muscle is comprised of approximately equal amounts of slow twitch type I and fast twitch type II (IIA, IIS) fibers. The muscles of both the nulliparous and multiparous beagles did not display any signs indicative of denervation or myopathology. The multiparous dogs exhibited significantly increased mean absolute muscle (1720 mm(3)) and total fiber-type I volumes (850 mm(3)) as well as relevantly increased mean diameter of type I fibers (72.0 microm) when compared with the nulliparous group. The canine levator ani (pubocaudal) muscle is not pathologically affected by vaginal deliveries and seems to adapt to numerous successive pregnancies and births through fiber-type I hypertrophy.     

A comparison of quantitative ultrastructural and contractile characteristics of muscle fibre types of the perch,Perca fluviatilis L.

Summary Quantitative ultrastructural and physiological parameters were investigated in three types of muscle fibres ofPerca fluviatilis: white fibres from the m. levator operculi anterior, pink (intermediate) fibres of the m. hyohyoideus and deep red fibres of the m. levator operculi anterior. Times to peak tension and half relaxation times of isometric twitches increased in the mentioned order. The extent of contact between the T system and the sarcoplasmic reticulum and the relative volume and surface area of the terminal cisternae showed an inverse relation with the time to peak tension of the twitch. The maximal isometric tetanic force per unit cross section area was similar for all three investigated types. The inverse relation between the time to peak tension of the twitch and the relative length of contact between T system and SR is in agreement with data obtained for fast- and slow twitch muscle fibres of the carp,Cyprinus carpio L.Abbreviations LOPA musculus levator operculi anterior - HH musculus hyohyoideus - SR Sarcoplasmic reticulum     

Muscle architecture and intramuscular distribution of nerves in the human soleus muscle

On the deep anterior surface of the human soleus muscle a bipenniform part is found, the portio anterior, which is innervated by the ramus anterior. This part and the innervation pattern are morphological characteristics peculiar to man. In six human soleus muscles plus three anomalies, the intramuscular distribution of the nerves supplying these muscles was macroscopically examined. In the normal soleus muscles, the R. anterior supplied not only the portio anterior but also the portio posterior through several anastomoses with twigs of the R. posterior. In the soleus without the portio anterior, the R. anterior entered the muscle at the anterior surface and joined directly with the branches of the R. posterior. In the soleus with two bipenniform parts, one bipenniform part was supplied by the R. anterior, and the other by the R. posterior. The cross-sectional area of the total nerves supplying the muscle was 0.72 +/- 0.036 mm2 (n = 8). The areas of the R. posterior and the R. anterior were in inverse relation to each other. These findings suggest that the R. anterior became separated from the R. posterior. However, the endoperineurium fiber composition of the R. anterior appeared to consist of a few nerve fiber components different from those of the R. posterior.     

A shell finite element model of the pelvic floor muscles

The pelvic floor gives support to the organs in the abdominal cavity. Using the dataset made public in (Janda et al. J. Biomech. (2003) 36(6), pp. 749-757), we have reconstructed the geometry of one of the most important parts of the pelvic floor, the levator ani, using NURB surfaces. Once the surface is triangulated, the corresponding mesh is used in a finite element analysis with shell elements.Based on the 3D behavior of the muscle we have constructed a shell that takes into account the direction of the muscle fibers and the incompressibility of the tissue. The constitutive model for the isotropic strain energy and the passive strain energy stored in the fibers is adapted from Humphrey's model for cardiac muscles. To this the active behavior of the skeletal muscle is added.We present preliminary results of a simulation of the levator ani muscle under pressure and with active contraction. This research aims at helping simulate the damages to the pelvic floor that can occur after childbirth.     

The distribution and colocalization of neuropeptides and 5-hydroxytryptamine in pelvic nerves supplying the posterior large intestine of the toad,Bufo marinus

The distribution and colocalization of neuropeptides and 5-hydroxytryptamine in the posterior portion of the large intestine of the toad was studied using single- and dual-label immunohistochemistry. Neurons containing colocalized galanin/somatostatin or vasoactive intestinal peptide alone were observed along intramural pelvic nerves. Some of the galanin/somatostatin neurons also contained 5-hydroxytryptamine. Synaptic boutons containing colocalized calcitonin gene-related peptide/vasoactive intestinal peptide were associated with the galanin/somatostatin neurons. The muscle of the large intestine was also innervated by axons containing galamin/somatostatin, vasoactive intestinal peptide/calcitonin gene-related peptide or vasoactive intestinal peptide alone. Nerve fibres containing calcitonin gene-related peptide/substance P, probably representing primary afferent nerves, were also associated with muscle bundles. Submucosal blood vessels carried dense plexuses of fibres containing vasoactive intestinal peptide alone or and calcitonin gene-related peptide/substance P. Adrenergic perivascular nerves also contained galanin and neuropeptide Y.     

Functional properties of muscle autografts substituted for the rat levator ani muscle

The present report deals with the functional properties (contraction parameters and neuromuscular transmission) of muscle grafts and transposed muscles substituted for the levator ani muscle in the rat. The experiments were divided into four main groups. Group I - the levator ani [LA] was excised and replaced in its own bed. Group II - the extensor digitorum longus, a fast muscle (with or without predenervation), and Group III - the soleus, a slow twitch muscle, were substituted for the LA. In group IV, the gracilis anterior muscle was either freely grafted in place of the LA or transposed a) with intact innervation, b) with its vascular supply intact or c) with preserved neuro-vascular supply. The optimum results of twitch and tetanic tension, and the amplitude of stimulation EMG responses was found in the case of LA resutured into its own bed and in the case transposition of the gracilis anterior muscle had been performed with its neuro-vascular supply intact in place of the LA. On the basis of these functional findings and morphological and anatomical observations (Grim et al. 1982), a surgical procedure is suggested for patients with anal incontinence (Grim et al. 1981, Dittertová-Vlasáková et al. 1982).     

A histochemical study of the innervation of the cerebral blood vessels in the domestic fowl

Summary Adrenergic and cholinergic nerves innervating the cerebral arteries of the domestic fowl were examined by specific histochemical techniques.The adrenergic nerve plexuses of the cerebral carotid system are markedly denser than those of other vertebrates observed by similar techniques. They form longitudinally elongated meshworks of fine fibres in the vascular wall of the arterial branches. Those innervating the vertebro-basilar system are less dense and more elongated, and, as the size of the artery diminishes, the fibres of the plexus become coarser. In the small pial and parenchymal arteries they are reduced to a few fibres running parallel to, or spiralling around the vascular axis.The cholinergic nerve plexuses are not as dense as the adrenergic system. The acetylcholinesterase activity is very weak, except in the plexuses innervating the cerebral carotid artery and the proximal portion of the anterior and posterior rami. In the vertebro-basilar system, a few thick nerve bundles run alongside the blood vessels of the vertebral and basilar arteries. Cholinergic nerves enter the cranial cavity along the internal carotid, the vertebral and possibly the cerebro-ethmoidal arteries.Intracerebral capillaries and some arterioles are not innervated with cholinergic and adrenergic fibres of peripheral origin, but with ones arising from parenchymal nerve cells.     

前后联合入路微创治疗合并神经损伤的不稳定骶骨骨折

目的:探讨前后联合入路锁定加压钢板(LCP)微创治疗合并神经损伤的骶骨不稳定骨折的效果。方法:前后联合入路按照杜明奎等方法[1]采用LCP固定治疗合并神经损伤的不稳定骶骨骨折患者5例:L5神经根损伤2例,骶丛神经损伤3例。前方入路暴露骨盆前环重建钢板固定,后方入路经皮下锁定加压钢板骨折复位固定术,椎管探查减压以MRI显示有无神经压迫为据。结果:5例均获随访,时间3～20(14.8±7.2)个月。2例L5神经根损伤和3例骶丛神经损伤者Frankel分级由C级恢复至E级,术后功能根据Matta评分标准评定:优3例,良2例。结论:前后联合入路LCP微创治疗合并神经损伤的骶骨不稳定骨折是一种简单微创有效的方法,值得临床推广。