排粪时胸肌、膈肌、腹壁肌及盆膈肌收缩，均压迫消化管。
Chest , abdominal , and pelvic muscles are used to pass them .
肛直肠线、直肠盆膈结合部与尾骨尖几乎处于同一个平面上。
The anorectal line , the point of rectum passing through the pelvic diaphragm and the coccygeal tip are almost at the same level .
盆膈盆膈盆膈