螺旋桨技术联合多序列在肛周脓肿中的诊断价值

目的 探讨MRI中运用螺旋桨技术联合多序列对肛周脓肿的诊断价值。方法 选择肛周脓肿的患者49例,其中男性40例,女性9例;年龄12～75岁,平均年龄39.6岁。采用3.0 T GE 750W MRI扫描仪,所扫序列均结合Propeller技术,行盆腔MRI检查。分析病灶在MRI分型、瘘管走行轨迹及内口的显示,并与病理诊断、肛门指检结果对照。结果 经病理诊断结果显示,肛周皮下脓肿29例,坐骨直肠窝脓肿10例,骨盆直肠间脓肿5例,直肠后间隙脓肿4例,直肠黏膜下脓肿1例。与病理诊断对照,MRI检出率100%,准确度96%;手术发现低位脓肿39例,高位脓肿10例。MRI对于高位肛周脓肿及低位肛周脓肿瘘管内口的检出率皆高于直肠指检（66.7%vs 11.1%、63.4%vs 39.0%）,且对于低位肛周脓肿瘘管内口检出差异有统计学意义（63.4%vs 39.0%。P=0.021）。扩散加权成像（DWI）脓肿壁呈等信号,增强后脓肿壁见强化;瘘管呈等T1、稍长T2（抑脂）信号,增强后呈管条状强化,内口周围亦可见片状强化。结论 MRI检查较好地显示肛周脓肿、瘘管轨迹、瘘管内口及与周围组织关系,为临床方...     

动态应力钢板与AO钢板对羊股骨干骨折愈合的影响

背景：目前钢板内固定治疗骨折愈合出现应力遮挡影响骨折愈合。 目的：观察动态应力钢板(CO钢板)与普通应力钢板(AO钢板)治疗羊股骨干骨折愈合的效果。 方法：24只山羊制备股骨干骨折模型,造模后随机分为2组,AO钢板组和CO钢板组分别用AO、CO钢板内固定,分别在1,2,3周取出股骨,常规行X射线与磁共振扫描。 结果与结论：X射线显示1周时,两组钢板骨折断端均未见明显变化,骨折线清晰可见;2周AO钢板组骨折断端无明显变化,骨折线明显,CO钢板组骨折断端骨密度增高,骨折线开始变模糊;3周AO钢板组骨折断端骨密度增加,CO钢板组骨折断端骨密度继续增高,出现云絮状外骨痂。MRI显示1周时,两组钢板骨折断端T1WI呈高信号,T2WI压脂序列上呈低信号,但AO钢板组骨折断端PDIR-TSE呈低信号,CO钢板组呈高信号。2周时两组骨折断端T1WI呈等或高信号,在T2WI压脂序列上呈等或低信号,AO钢板组PDIR-TSE呈低信号,CO钢板组呈高信号。3周AO钢板组可见骨折线明显,骨折断端在T1WI呈等或低信号,在T2WI压脂序列上呈等低信号,PDIR-TSE呈低信号;CO钢板组骨折断端可见骨折线模糊,骨折断段在T1WI上呈等或高信号,在T2WI压脂序列上呈等或低信号,PDIR-TSE呈等或高信号。提示CO钢板组骨折断端的血液循环、骨痂含量均优于AO钢板组骨折断端。     

MRI在子宫内膜间质肉瘤中的诊断价值

目的探讨MRI在子宫内膜间质肉瘤中的诊断价值。方法回顾性分析2012年-2016年经手术病理证实为子宫内膜间质肉瘤的MRI影像特点。结果病理证实13例子宫内膜间质肉瘤。低级别9例,高级别4例。5例发生于子宫肌壁间,2例在宫腔内,肌壁间及宫腔内同时发生2例,2例在宫颈,2例在子宫外。13例病例T1WI均呈等信号为主。T2WI呈稍高信号为主。13例DWI均呈高信号。结论 MRI在诊断子宫内膜间质肉瘤中有很高的诊断价值。     

骨化性肌炎的MRI表现特点与演变

目的分析骨化性肌炎的MRI表现特点与演变规律,以提高其诊断和鉴别诊断的水平。方法对13例患者（男性4例,女性9例,年龄11～65岁,平均年龄39.69岁）经手术或穿刺组织病理学诊断证实为骨化性肌炎的共16例次MRI检查图像进行回顾性分析。结果早期（2～3周,4例次）为边界不清的T1WI中等偏高信号、T2WI高信号为主的软组织肿块;中期（1-12个月,11例次）：T1WI由不均匀中等偏高信号逐渐变为中低信号,T2WI以团块和分叶状不均匀中低信号为主,夹杂有片状高信号区的软组织肿块,周边有低信号带形成。1例次内见有出血和液一液平,周围的水肿带（T1WI低信号、T2WI高信号）变窄。晚期（1～2年,1例次）：肿块缩小,T1WI和BWI上以高信号为主,夹杂有条带状低信号影。结论骨化性肌炎MRI表现有一定的特点和变化规律．具有一定的特征性．提高对其MRI表现的认识有助于诊断和鉴别诊断．避免不必要的手术。     

唾液腺黏液表皮样癌磁共振成像表现

目的分析唾液腺黏液表皮样癌磁共振成像(MRI)特征,提高对黏液表皮样癌(MEC)的认识。方法回顾性分析经我院手术病理证实的20例唾液腺黏液表皮样癌患者的MRI表现,重点观察T2压脂上信号强度及囊变情况,并与组织病理特征对照分析。结果高级别MEC 2例,T2WI及T2压脂上均呈不均匀低-中信号,无囊变;中等级MEC 12例,T2WI及T2压脂上均呈不均匀中-高信号,11例(91. 7%)有囊变,1例(8. 3%)无囊变;低级别MEC 6例,T2WI及T2压脂上均呈不均匀中-高信号,6例(100%)均有囊变,其中1例(16. 7%)合并淋巴结转移; T1WI上20例MEC均表现低信号,增强扫描显示18例肿瘤内部实性成分呈较明显强化; 16例边界不清楚,4例边界清楚。结论唾液腺黏液表皮样癌MRI表现具有一定特征性,MRI表现能反映肿瘤组织病理学性质,可为临床诊断及治疗提供帮助。     

韧带样瘤MRI表现与病理组织分析

目的回顾性分析韧带样瘤的影像表现和病理学特征,提高对该病的术前诊断符合率。方法选择2011年1月至2015年1月在东南大学附属第二医院9例病理诊断为韧带样瘤患者,其中女性6例,男性3例;年龄31~34岁,中位年龄35岁。行CT、MRI常规T1加权成像(T1WI)、T2加权成像(T2WI)、短时间反转恢复(STIR)序列扫描。手术后取病灶组织进行病理组织检查,分析影像学表现及病理学特征。结果 CT表现为局部软组织肿块,边界不清,密度欠均。MRI图像,呈等T1稍长或等T2信号,压脂像呈高信号,部分内见条片状低信号,坏死囊变少见,增强扫描均有明显不均匀强化,上述病例未见转移征象。结论韧带样瘤的影像学表现中,MRI表现较具有特征,在T1WI及T2WI可见条状低信号,部分病灶呈爪状,侵袭性生长,掌握其影像特征,可以提高该病的诊断符合率。     

子宫内膜异位症的MRI影像病理学研究

目的分析子宫内膜异位症的磁共振(MRI)影像特征. 材料与方法回顾性分析51例子宫内膜异位症的MRI影像特征,全部病例经手术及病理证实. 结果子宫增大48例;T2WI及T1WI显示子宫有弥散分布的片状低信号区内夹杂斑点状高信号30例; T2WI显示子宫低信号区内夹杂斑点状高信号,T1WI呈低信号21例.29个卵巢囊肿,T1WI 及T2WI均呈高信号有15个,T1WI 呈高信号而T2WI呈低或等信号5个, T1WI 和T2WI均呈混杂信号9个. 结论子宫内膜异位症的主要MRI表现:(1)子宫内出现片状低信号区,同时夹杂斑点状高信号;(2)卵巢巧克力囊肿在T1WI 和T2WI均为高信号或以高信号为主的混杂信号.     

颅内皮样囊肿破裂4例的MRI诊断

目的分析颅内皮样囊肿破裂的MRI表现。方法搜集4例经手术病理证实颅内皮样囊肿破裂病例资料,均行MRI平扫及增强检查,对其MRI表现、病因、病理和临床特征进行分析。结果病灶位于鞍旁2例,位于后颅窝及第三脑室后各1例。3例MRI表现T1WI与T2WI均为高信号,1例MRI表现T1WI为不均匀稍低信号,T2WI为高信号影。结论颅内皮样囊肿破裂有较典型的MRI影像学和临床特征性表现,可实现术前正确诊断。     

子宫内膜异位症的MRI影像病理学研究

目的 分析子宫内膜异位症的磁共振（MRI）影像特征。材料与方法 回顾性分析51例子宫内膜异位症的MRI影像特征，全部病例经手术及病理证实。结果 子宫增大48例；T2WI及T1WI显示子宫有弥散分布的片状低信号区内夹杂斑点状高信号30例；T2WI显示子宫低信号区内夹杂斑点状高信号，T1WI呈低信号21例，29个卵巢囊肿，T1WI及T2WI均呈高信号有15个，T1WI呈高信号而T2WI呈低或等信号5个，T1WI和T2WI均呈混杂信号9个。结论 子宫内膜异位症的主要MRI表现：（1）子宫内出现片状低信号区，同时夹杂斑点状高信号；（2）卵巢巧克力囊肿在T1WI和T2WI均为高信号或以高信号为主的混杂信号。     

相位阵列线圈高分辨MRI显示肛管和肛周结构及其意义

目的：探讨应用体外相位阵列线圈高分辨MRI技术对肛管和肛周结构显示的可行性及其价值.方法：应用体外圆形极化相位阵列脊柱线圈对20例健康志愿者进行了高分辨MR扫描,扫描序列包括轴位T1WI,轴位、矢状和冠状平面T2WI及Gd-DTPA增强扫描的T1WI,轴位和冠状扫描平面分别垂直和平行于肛管的长轴.结果：肛管的粘膜、粘膜下层、肛门括约肌及会阴部结构如会阴体、会阴浅横肌、球海绵体肌、坐骨海绵体肌等在T2WI上均可清楚显示.男性和女性的肛管结构存在差异,女性外括约肌的前部明显短于后部,会阴体较男性大,而男性的球海绵体肌较女性厚.结论：体外相位阵列线圈高分辨MRI技术可清楚显示肛管和肛周结构的正常解剖,可为肛管区域病变的正确诊断和治疗提供较精确的解剖信息.     

MRI不同序列对骶髂关节软骨成像的比较

背景：平片及CT不能显示关节软骨的改变,磁共振虽可显示软骨,但常规序列软骨显像效果欠佳,因此若要提高MRI检出软骨病变的能力,序列的优化显得非常重要。 目的：比较骶髂关节常用磁共振成像序列,筛选适合骶髂关节软骨MRI最佳成像序列。 方法：对45健康志愿者分别行骶髂关节MRI自旋回波T1WI、T2WI、T1-flash-3d-water-cor、T2-me3d-cor和T2-me2d-cor和T1-se-cor-water-fil扫描,比较各个序列显示骶髂关节软骨的清晰度、内部信号变化及软骨表面缺损。 结果与结论：自旋回波T1WI和T2WI序列45均显示骶髂关节软骨为一条稍高信号带,关节间隙不清;梯度回波T1-se-cor-water-fil序列45均显示两侧关节面骨皮质与髂侧软骨、骶侧软骨及软骨间隙形成的5条平行线状结构;T2-me3d-cor、T1-flash-3D-water-cor-fil序列45例受检者关节软骨为一条明亮、清晰高信号,与周围骨皮质及骨髓分界非常清晰,但骶侧、髂侧软骨不能够区分。T2-me2d-cor序列 37例能显示髂侧、骶侧软骨及软骨间关节间隙,8例分辨不清;弥散成像序列仅部分层面能显示关节软骨,诸结构显示较模糊,信号强度对比不鲜明。结果说明,T1-se-cor-water-fil在关节软骨显示程度、内部信号变化和软骨表面缺损程度等方面明显优于其他序列。T1-flash-3d-water-cor、T2-me3d-cor和T2-me2d-cor对软骨表显示方面优于常规MRI序列,但不如T1-se-cor-water-fil。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程      

Development of the external anal sphincter with special reference to intergender difference: observations of mid-term fetuses (15-30 weeks of gestation)

To investigate intergender differences in muscle cleavage and joining during development of the external anal sphincter (EAS), we examined semiserial sections of 16 fetuses between 15 and 30 weeks of gestation (6 males and 10 females). The subcutaneous part of the EAS (EASsc) developed along the male perineal raphe and extended posteriorly. Thus, the male EAS was characterized by anterior protrusion of the subcutaneous muscle, in contrast to the almost circular female EAS. In both genders, the bulbospongiosus anlage (or the levator ani anlage) issued muscle fibers to form the superficial (or deep) part of the EAS. The EASsc communicated with the superficial part in males, whereas the female bulbospongiosus tended to communicate with the levator ani rather than the EAS. In both genders, the longitudinal muscle bundle(s) of the anorectum contributed to perineal body formation. However, the male perineal body also had a thick fascia between the rhabdosphincter and the levator. The bulbospongiosus seems to play a critical role in forming the EAS. A strict intergender difference in subcutaneous muscle development is evident along the perineal raphe, as the raphe is not evident in females. These results help to explain variations in the EAS, including anal malformations.     

Anococcygeal raphe revisited: a histological study using mid-term human fetuses and elderly cadavers

Purpose

We recently demonstrated the morphology of the anococcygeal ligament. As the anococcygeal ligament and raphe are often confused, the concept of the anococcygeal raphe needs to be re-examined from the perspective of fetal development, as well as in terms of adult morphology.

Materials and Methods

We examined the horizontal sections of 15 fetuses as well as adult histology. From cadavers, we obtained an almost cubic tissue mass containing the dorsal wall of the anorectum, the coccyx and the covering skin. Most sections were stained with hematoxylin and eosin or Masson-trichrome solution.

Results

The adult ligament contained both smooth and striated muscle fibers. A similar band-like structure was seen in fetuses, containing: 1) smooth muscle fibers originating from the longitudinal muscle coat of the anal canal and 2) striated muscle fibers from the external anal sphincter (EAS). However, in fetuses, the levator ani muscle did not attach to either the band or the coccyx. Along and around the anococcygeal ligament, we did not find any aponeurotic tissue with transversely oriented fibers connecting bilateral levator ani slings. Instead, in adults, a fibrous tissue mass was located at a gap between bilateral levator ani slings; this site corresponded to the dorsal side of the ligament and the EAS in the immediately deep side of the natal skin cleft.

Conclusion

We hypothesize that a classically described raphe corresponds to the specific subcutaneous tissue on the superficial or dorsal side of the anococcygeal ligament.     

女性压力性尿失禁患者盆底肌形态改变的磁共振成像评价

目的 磁共振成像(MRI)技术探讨女性压力性尿失禁(SUI)患者盆底肌形态的改变.方法 自2006年1月至2008年6月间,21例SUI患者(尿失禁组)以及10例正常控尿成年女性(对照组)入组研究.所有对象均分别在平静状态以及屏气用力状态下行盆腔MRI扫描.分析尿失禁组和对照组两种状态下耻骨直肠肌厚度以及肛提肌裂隙面积的变化情况与SUI之间的关系.结果 无论在平静或屏气用力状态下,尿失禁组左、右侧耻骨直肠肌厚度均较对照组薄(均P<0.05).尿失禁组肛提肌裂隙多呈横径增宽的纵向椭圆形,平静状态下裂隙面积较对照组大[(1893.44±218.44)mm2比(1661.86±206.62)mm2,P<0.05].尿失禁组阴道呈"H"形占33.3%(7/21),提示存在阴道侧壁损伤占66.7%(14/21);对照组阴道呈"H"形占80.0%(8/10).尿失禁组阴道侧壁损伤明显高于对照组(P<0.05).结论 女性压力性尿失禁患者左、右侧耻骨直肠肌厚度变薄,肛提肌裂隙明显增大.MRI在评价女性SUI患者的肛提肌形态改变的检测中结果可信,能为临床治疗提供明确信息.     

In vivo visualization of the levator ani muscle subdivisions using MR fiber tractography with diffusion tensor imaging

Understanding the levator ani complex architecture is of major clinical relevance. The aim of this study was to determine the feasibility of magnetic resonance (MR) fiber tractography with diffusion tensor imaging (DTI) as a tool for the three-dimensional (3D) representation of normal subdivisions of the levator ani. Ten young nulliparous female volunteers underwent DTI at 1.5 T MR imaging. Diffusion-weighted axial sequence of the pelvic floor was performed with additional T2-weighted multiplanar sequences for anatomical reference. Fiber tractography for visualization of each Terminologia Anatomica-listed major levator ani subdivision was performed. Numeric muscular fibers extracted after tractography were judged as accurate when localized within the boundaries of the muscle, and inaccurate when projecting out of the boundaries of the muscle. From the fiber tracking of each subdivision the number of numeric fibers (inaccurate and accurate) and a score (from 3 to 0) of the adequacy of the 3D representation were calculated. All but two volunteers completed the protocol. The mean number of accurate fibers was 17 ± 2 for the pubovisceralis, 14 ± 6 for the puborectalis and 1 ± 1 for the iliococcygeus. The quality of the 3D representation was judged as good (score = 2) for the pubovisceralis and puborectalis, and inaccurate (score = 0) for the iliococcygeus. Our study is the first step to a 3D visualization of the three major levator ani subdivisions, which could help to better understand their in vivo functional anatomy.     

视神经磁共振成像方法研究

目的　探讨视神经磁共振 (MRI)成像最佳方法及正常视神经MRI征象 .方法　随机选择 4 0例进行头部检查 ,无眼部疾患或视力障碍患者作为正常视神经研究对象 .使用PhilipsACS -NT15 1.5T超导型磁共振成像仪及正交头线圈 .成像序列包括自旋回波T1加权成像 (SET1WI)及超快速自旋回波加或不加脂肪频谱饱和技术成像 (TSE±SPIRT2WI) .扫描方位包括与视神经平行轴位、斜矢状位及与视神经长轴垂直冠状位和标准冠状位 .结果　视神经眶内段、管内段及视束粗细均匀 .SET1WI显示视神经较周围的蛛网膜下腔信号强度稍高 ,T2WI显示视神经呈相对低信号 ,与脑髓质信号相等 ,周围包绕高信号脑脊液 .与视神经长轴平行的轴位及斜矢状位T1WI及T2WI均可显示视神经全貌 ,与视神经长轴垂直冠状位TSE +SPIRT2WI技术显示视神经信号均匀 .结论　MRI可以较好地显示视神经解剖 ,与视神经长轴垂直冠状位TSE +SPIRT2WI可以较好地显示信号特征 .     

Descriptive epidemiology of isolated anal anomalies: A survey of 4.6 million births in Europe

The prevalence of anal anomalies among 4,618,840 births recorded in 33 EUROCAT registries between 1980 and 1994 was 4.05 per 10,000 births. Of the 1,846 recorded cases, 672 (36.4%) were isolated anal anomalies while 1,174 (63.6%) occurred together with other anomalies. Only isolated anal anomalies were analyzed in this study: 75.5% were atresias, 10.1% of which were above and 89.9% were below the level of the levator ani muscle. Fistula occurred in 53% of supralevator and 37% of infralevator atresia. Other anal anomalies were ectopic anus (3.4%), congenital anal fistula (14.7%), and persistent cloaca (0.9%). There was a predominance of males in anal atresia without fistula (male to female (M:F) ratio was 6.7 for supralevator and 2.3 for infralevator atresia), but no significant sex difference in atresias with fistula. There was a predominance of females in ectopic anus and congenital anal fistula (M:F = 0.11 and 0.36 respectively). High frequencies of fetal deaths were recorded in supralevator atresia without fistula (8.3%) and in persistent cloaca (11.1%). Mean gestational length and mean birth weights were reduced for persistent cloaca but were within normal limits for other isolated anal anomalies. Odds ratios (ORs) for mothers above 35 years were increased for supralevator atresia without fistula, supralevator atresia with fistula, and congenital anal fistula. ORs for mothers below 30 years were slightly increased for supralevator atresia without fistula and decreased for persistent cloaca. There were marked differences in prevalence and distribution of anal anomalies among the EUROCAT registries. The results indicated that there are epidemiological differences among the various types of anal anomalies which might reflect different embryological origins. © 2001 Wiley‐Liss, Inc.     

Descriptive epidemiology of isolated anal anomalies: a survey of 4.6 million births in Europe.

The prevalence of anal anomalies among 4,618,840 births recorded in 33 EUROCAT registries between 1980 and 1994 was 4.05 per 10,000 births. Of the 1,846 recorded cases, 672 (36.4%) were isolated anal anomalies while 1,174 (63.6%) occurred together with other anomalies. Only isolated anal anomalies were analyzed in this study: 75.5% were atresias, 10.1% of which were above and 89.9% were below the level of the levator ani muscle. Fistula occurred in 53% of supralevator and 37% of infralevator atresia. Other anal anomalies were ectopic anus (3.4%), congenital anal fistula (14.7%), and persistent cloaca (0.9%). There was a predominance of males in anal atresia without fistula (male to female (M:F) ratio was 6.7 for supralevator and 2.3 for infralevator atresia), but no significant sex difference in atresias with fistula. There was a predominance of females in ectopic anus and congenital anal fistula (M:F = 0.11 and 0.36 respectively). High frequencies of fetal deaths were recorded in supralevator atresia without fistula (8.3%) and in persistent cloaca (11.1%). Mean gestational length and mean birth weights were reduced for persistent cloaca but were within normal limits for other isolated anal anomalies. Odds ratios (ORs) for mothers above 35 years were increased for supralevator atresia without fistula, supralevator atresia with fistula, and congenital anal fistula. ORs for mothers below 30 years were slightly increased for supralevator atresia without fistula and decreased for persistent cloaca. There were marked differences in prevalence and distribution of anal anomalies among the EUROCAT registries. The results indicated that there are epidemiological differences among the various types of anal anomalies which might reflect different embryological origins.     

Human fetal anatomy of the coccygeal attachments of the levator ani muscle

In contrast to the attachments to the pubis and rectum, there is little information on fetal development of the coccygeal attachment of the levator ani muscles. We find that at 9 weeks, the coccygeus muscle is a large muscle facing the piriformis or gluteus maximus and inserting onto the ischial spine, whereas the levator ani is restricted to the area near the pubis. By 12 weeks, the levator ani also obtains attachment to the ischial spine immediately ventral to the coccygeus muscle. The most superior part of the coccygeus muscle occupies a space at an angle between the pelvic splanchnic and pudendal nerves. Notably, medial to the coccygeus muscle, a third parasagittal muscle (previously termed the sacrococcygeus anterior) appears by 12 weeks, increases in mass by 18 weeks, and connects and mixes with the dorsal end of the levator ani by 18–20 weeks. Thus, the coccygeal attachment of the levator ani appears not to depend on the dorsal extension of the muscle itself but on fusion with the sacrococcygeus anterior. Therefore, the final levator sheet is formed medial (internal) to the coccygeus muscle and originates from two distinct anlage. Clin. Anat. 23:566–574, 2010. © 2010 Wiley‐Liss, Inc.     

Histo-topographic study of the longitudinal anal muscle

The longitudinal anal muscle (LAM) has been described as a vertical layer of muscular tissue interposed between the circular layers of the internal (IAS) and external (EAS) anal sphincters. There is, however, no general agreement in the literature on its composition and attachments. The aim of this study was to investigate the histological structure, attachments, and topography of the LAM in order to evaluate its role in continence and defecation, thus enhancing knowledge of the surgical anatomy of this region. After in situ formalin fixation, the pelvic viscera were removed from eight male and eight female cadavers (age range: 52-72 years). Serial macrosections of the bladder base, lower rectum and anal canal, cervix and pelvic floor complex, cut in the transverse (six specimens) and coronal (six specimens) planes, underwent histological and immunohistochemical studies. Four specimens were studied using the E12 sheet plastination technique. The LAM was identified in 10/12 specimens (83%). Transverse and coronal sections made clear that it is a longitudinal layer of muscular tissue, marking the boundary between the internal and external anal sphincters. From the anorectal junction it extends along the anal canal, receives fibers from the innermost part of the puborectalis and the puboanalis muscles, and terminates with seven to nine fibro-elastic septa, which traverse the subcutaneous part of the external anal sphincter, reaching the perianal dermis. In the transverse plane, the mean thickness of the LAM was 1.68 +/- 0.27 mm. Immunohistochemical staining showed that the LAM consists of predominantly outer striated muscle fibers and smaller numbers of inner smooth muscle fibers, respectively coming from the levator ani muscle and from the longitudinal muscular layer of the rectum. The oblique fibers suggest that the LAM may represent the intermediate longitudinal course of small bridging muscle bundles going reciprocally from the striated EAS to the smooth IAS and vice versa. The spatial result is the helical course of striated and smooth muscle fibers between the EAS and IAS, which contribute not only to the narrowing but also to some shortening of the anal canal during sphincter contraction. Thus, rather than being a boundary, the LAM gives anatomical evidence of a functional connection between two muscle systems with different structures and topography.