Three muscle slings of the pelvic floor in women: an anatomic study

The region anterior to the anal canalin women is composed of intertwined smooth and skeletal muscles. The present study aimed to clarify skeletal musclemorphology in the anterior region of the anal canal. The pelvic floor musclesof 28 pelvic halves from 16 female cadavers (mean age 79.75 years) were dissected from the inferior aspect to examine the perineal muscles, followed by midline transection and dissection from the inner surface to examine the pelvic outlet muscles. The bulbospongiosus musclewas found to be attached to the lateral surfaceof the external anal sphincter. The superficial transverse perineal musclecrossed superiorly to the bulbospongiosusand coursed medially toward its contralateral musclebundle deep to the anterior portion of the external anal sphincter. The superficial transverse perineal muscleformed the middle sling. From the medial aspect, the anterior part of the levator aniwas divided into anterior and posterior bundles to form the anterior and posterior slings, respectively. This study proposes that three muscular slings could be important in supporting the pelvic floorin women. In addition, this study shows that the anterior skeletal muscular wall of the anal canalis composed of the anterior musclebundle of the levator ani, superficial transverse perineal, and proper external anal sphincter muscles.