Matzel K E, Schmidt R A, Tanagho E A
Department of Urology, University of California, San Francisco 94143-0738.
Dis Colon Rectum. 1990 Aug;33(8):666-73. doi: 10.1007/BF02150742.
The striated pelvic floor musculature and the striated muscle of the external and sphincter contribute to anal continence by effecting, respectively, the rectoanal angulation of the bowel and an anal high pressure zone. The muscular anatomy of the pelvic floor is generally understood, but the neuroanatomy remains controversial. The authors dissected three male cadavers and traced the sacral nerves from their entrance into the pelvis through the sacral foramina throughout their branching to their final destinations. Deriving from a common source, the sacral nerves S2 to S4, the neural supply of the levator ani was distinct from that of the external anal sphincter: the levator is supplied by direct branches splitting from the sacral nerves proximal to the sacral plexus and running on the inner surface; the external anal sphincter is supplied by nerve fibres travelling with the pudendal nerve on the levator's undersurface. To document the functional relevance of these anatomic findings, stimulation of the pudendal and sacral nerves was performed at different levels in five patients with lower urinary tract dysfunction. Stimulation of the pudendal nerve increased the anal pressure, whereas stimulation of S3 increased it only slightly but caused an impressive decrease of the rectoanal angle; when S3 was stimulated after bilateral pudendal block, anal pressure did not change but the decrease in the rectoanal angulation persisted. The changes in anal pressure could be obtained without fatigue at stimulation frequencies of 10 to 20 Hz.
盆底横纹肌以及外括约肌的横纹肌分别通过影响肠管的直肠肛管角度和肛管高压区来维持肛门节制功能。盆底的肌肉解剖结构已基本明确，但神经解剖结构仍存在争议。作者解剖了三具男性尸体，追踪骶神经从通过骶孔进入骨盆直至其分支到达最终目的地的全程。肛提肌的神经供应源自共同的骶神经S2至S4，与肛门外括约肌的神经供应不同：肛提肌由在骶丛近端从骶神经直接发出并走行于其内表面的分支供应；肛门外括约肌由在肛提肌下表面与阴部神经伴行的神经纤维供应。为证明这些解剖学发现的功能相关性，对5名下尿路功能障碍患者在不同水平刺激阴部神经和骶神经。刺激阴部神经可使肛管压力升高，而刺激S3仅使其略有升高，但导致直肠肛管角度显著减小；双侧阴部神经阻滞之后刺激S3，肛管压力未改变，但直肠肛管角度减小仍持续存在。在10至20Hz的刺激频率下，可无疲劳地获得肛管压力变化。
