Answer to Princess and the Pee

Question: Which of the indicated muscles represents the pubococcygeus? 

Correct answer is C, the pubococcygeus muscle. The pelvic floor principally consists of two funnel shaped muscles that originate from the pelvis and ileum, the levator ani muscles,  and meet in the middle. The levator ani muscles originate specifically from a ligamentous tendinous arch (now indicated in the image with asterisks) that covers the obturator internus muscle. Each levator ani muscle is further subdivided into a puborectalis, a pubococcygeus and iliococcygeus muscle. A second muscle, the coccygeus proper, is not part of the levator ani, but also contributes to the pelvic floor. To be fair, it is difficult to discern the boundary of the pubococcygeus and iliococcygeus muscles in the image. However, given the options, the most anterior component of the two labeled muscles is the acceptable answer. Also, it is the pubococcygeus portion of the levator ani that is often at risk of damage during vaginal delivery and the source of pelvic prolapse associated with urinary incontinence.

1.= Psoas major m.

2.= Obturator internus m.

3.= Pubococcygeus m.

4.= Iliococcygeus m.

5.= Piriformis m.

Answer to this question is based on material presented in lectures 2 of the Pelvis Lecture Series.