Pelvic floor muscles. Artwork of the female pelvic floor muscles, the interior boundary of the pelvis. These muscles maintain continence as part of the urinary and anal sphincters. The 3 red projections, from top to bottom are, the urethra, the vagina and the rectum. The muscle below them is the pubococcygeus, or PC muscle, which controls the flow of urine and contracts during orgasm. At top left and right are the obturator internus muscles, which attach to the pelvis and thigh bone. They stabilise the hip joint and laterally rotate the flexed thigh. Inside these muscles is the levator ani, which supports the pelvic organs and surrounds the anus and vagina.