**2.4 Pelvic floor**

The pelvic floor is a structure that forms the bottom of the pelvis, and plays an important role in supporting the pelvic organs. In the past, pelvic floor muscles could not be visualized clearly, however, the development of magnetic resonance imaging assessments and improvements in minimally invasive surgery techniques such as laparoscopy and robotic surgery can clearly show the anatomy of this region It is mainly composed of the levator ani muscle complex: pubococcygeus, iliococcygeus, and puborectalis muscle. The levator ani muscle received direct innervation from sacral nerve roots (S3-S5) and play an important role in cooperative action through coordinated contraction and relaxation during defecation [25]. The pubococcygeus is located in the most anterior portion of the levator ani muscles, and from both pubic bone to the coccyx. The iliococcygeus is the posterior part of the levator ani muscle and extends from the ischial spine to the anococcygeal raphe and coccyx. The puborectalis muscle, which is located below the pubococcygeus, forms a U-shaped ring around the rectum and makes an anorectal angle to prevent fecal incontinence. The coccygeus muscle, which is also a part of the pelvic floor, is located posterior portion of the levator ani muscle and reinforces the posterior pelvic floor (**Figure 8**) [20]. The pelvic floor has two hiatuses: the urogenital hiatus and the rectal hiatus. The rectal hiatus is located in the posterior of the pelvic floor through which the anal canal passes. The perineal body, a pyramidal fibromuscular mass, is located between the urogenital hiatus and the anal canal, strengthens the pelvic floor [26]. During distal rectal cancer surgery for sphincter preservation such as ISR, the intersphincteric space between the puborectalis muscle and the rectal wall should be identified, and the dissection continues down to the deep part of the anal canal through the intersphincteric space (**Figure 9**) [24]. On the other hand, during an abdominoperineal resection, the levator ani muscles must be cut [27].
