A 55-year-old woman complains of fecal incontinence. The most likely contributing factor to such a problem is atrophy, paralysis, or dysfunction of which of the following structures?

The pubococcygeus muscle, especially its most medial portion, the puborectalis, is of most importance in fecal continence. The levator ani consists of two major portions, the pubococcygeus and ilio- coccygeus, which help support pelvic viscera and resist increases in intraabdominal pressure. The puborectalis muscle is the most medial and inferior portion of the pubococcygeus. The puborectalis forms a loop around the rectoanal junction, and the integrity of this muscle is critical in maintenance of fecal continence. The coccygeus and pubovesicocervical fascia are not in direct contact with the rectum. Damage to the urogenital diaphragm can contribute to urinary incontinence but not fecal incontinence.