盆底序列解剖对肛门外括约肌复合体中间环的立体构象观察

目的通过盆底序列解剖,观察肛门外括约肌复合体中间环的立体构象特点,进一步分析肌肉收缩力的方向及特点.方法采取自行设计的盆底序列解剖方法,对18具无直肠肛门疾患尸体及1具先天性直肠肛门畸形新生儿尸体实施盆底局部精细解剖,获得完整的肛门外括约肌复合体标本,使用放大镜、解剖显微镜对肌肉的走形、分布特点进行观察.结果盆底序列解剖获得如下组成部分:完整骨盆及其全部连带结构,骨盆及其连带的全部盆底肌群,半开放的骨盆,盆底肌与骨盆骨性结构完全分离,肛门外括约肌复合体.外括约肌复合体中间环纤维环绕肛管前壁后于肛管后方交叉,两侧肌束于肛管两侧壁形成小U型结构;肛管前方肌纤维粗大,与肛管前壁附着疏松,后方肌纤维纤细含有纤维结缔组织,与肛管后壁附着紧密.结论序列盆底解剖可以确保获得完整的肛门外括约肌复合体标本.外括约肌复合体肌中间环纤维环绕肛管前壁后于肛管后方交叉,两侧肌束终止于肛管两侧壁,呈现出特有的小U型构象,对肛管侧壁形成压迫;肌纤维与肛管后壁紧密附着形成肌肉的作用止点,决定了中间环肌纤维向后的收缩力.

3D intermittent loop structure of external anal sphincter muscle complex observed through consequential dissection of pelvic floor

Objective To analyze the contraction direction and distribution of external anal sphincter muscle complex by observing its 3D intermittent loop structure through consequential dissection of pelvic floor.Methods Intact external anal sphincter muscle complex samples were taken from 18 cadavers without anorectal disease and 1 neonate cadaver with congenital anorectal malformation using self-designed consequential dissection method of pelvic floor.The characteristics of direction and distribution of external anal sphincter muscle complex were observed under magnifier and anatomic microscope.Results The following were observed,including intact pelvic and its associated structures,pelvic and its associated muscles,semi-open pelvic,pelvic muscles completely isolated from pelvic bone structure,intact external anal sphincter muscle complex,intermittent loop fibers of external anal sphincter muscle complex crossing posterior to the anal canal with small U image lateral to the anal canal,strong and dense muscle fibers crossing anterior to the anal canal with anterior paries loosely connected,slim and loose posterior fibers filled with connective fibers and tightly connected with anal canal posterior wall.Conclusion Intact external anal sphincter muscle complex samples can be taken by consequential dissection of pelvic floor.Intermittent loop fibers of external anal sphincter muscle complex surround the anal canal anterior wall and then cross at the anal canal posterior wall with its lateral muscle bundles terminated at the anal canal walls characterized by small U fibers and compression on the anal canal walls.The contraction of intermittent loop fibers depend on the end action point of muscles tightly attached to the muscle fibers and the anal canal posterior wall.