The roof of the perineum is formed mainly by the levator ani muscles that separate the pelvic cavity, above, from the perineum, below. These muscles, one on each side, form a coneor funnel-shaped pelvic diaphragm, with the anal aperture at its inferior apex in the anal triangle.
Anteriorly, in the urogenital triangle, a U-shaped defect in the muscles, the urogenital hiatus, allows the passage of the urethra and vagina.