Muscles of the Pelvic Floor and Perineum

The pelvic diaphragm marks the inferior margin of the abdominopelvic cavity. It is formed by the paired levator ani and coccygeus muscles, which attach to the internal walls of the true pelvis.

While the pelvic diaphragm is penetrated by the anal canal and urethra in both sexes, females have the vagina as an additional opening.

The levator ani is the largest three-part muscle of the pelvic floor, comprising the pubococcygeus, the puborectalis, and the iliococcygeus muscles.

It primarily supports pelvic organs, such as the bladder, and acts as a sphincter at the anorectal junction, urethra, and vagina.

Under the pelvic diaphragm lies the diamond-shaped region called the perineum.

It is divided into an anterior urogenital triangle, housing the external genitals, and a posterior anal triangle, which contains the anus.

The urogenital triangle includes the superficial transverse perineal, bulbospongiosus, and ischiocavernosus muscles of the external genitalia.

The anal triangle has the anal canal surrounded by the external anal sphincter. Its other prominent muscles include the obturator internus and the inferior region of the levator ani.