Department of Gynecology, Tohoku University School of Medicine, Sendai, Japan.
Clin Anat. 2010 Jul;23(5):566-74. doi: 10.1002/ca.20983.
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.
与耻骨和直肠的附着不同，关于肛提肌尾骨附着的胎儿发育，信息很少。我们发现，在 9 周时，尾骨肌是一块面向梨状肌或臀大肌并插入坐骨棘的大肌肉，而肛提肌则局限于耻骨附近的区域。到 12 周时，肛提肌也开始在尾骨肌的腹侧附着于坐骨棘。尾骨肌的最上部占据了盆腔内脏和阴部神经之间的一个角度空间。值得注意的是，在尾骨肌的内侧，第三矢状旁肌肉（以前称为前骶尾骨肌）在 12 周时出现，到 18 周时质量增加，并在 18-20 周时与肛提肌的背侧末端连接和混合。因此，肛提肌的尾骨附着似乎不是依赖于肌肉本身的背侧延伸，而是依赖于与前骶尾骨肌的融合。因此，最终的肛提肌板形成于尾骨肌的内侧（内部），并由两个不同的原基起源。
