• Pubococcygeal line (PCL) extends from inferior margin of the symphysis to the last coccygeal disc space.

• Anorectal junction is the point of taper of the distal part of the rectum as it meets the anal canal, corresponding to the posterior impression of the transition between puborectalis muscle and levator plate.

• H Line (levator hiatus) - line drawn from the inferior border of the pubic symphysis to the posterior wall of the rectum at the level of the anorectal junction.

• M Line - vertical line drawn perpendicularly from the PCL to the most posterior aspect of the H line.

• Puborectalis muscle forms a sling around the anorectal junction and is part of the external anal sphincter.

• Levator ani muscle consists of the ileococcygeus, pubococcygeus and puborectalis muscles. The ileococcygeus and pubococcygeus muscles are best seen on coronal images. Posteriorly they fuse anterior to the coccyx to form the levator plate.

• Rectocele - prolapse of the rectal wall > 2 cm anterior to the expected margin of the rectal wall.

• Rectoanal mucosal intussusception - rectal mucosal invagination that descends toward the anal canal.

• Rectal prolapse - most severe form of intussusception where rectal mucosa protrudes through the anal orifice.

• Pelvic floor dyssynergia - failure of relaxation or a paradoxical contraction of the pelvic floor muscles with defecation, symptoms of constipation, manual maneuvers for defecation, thickened contracted puborectalis.

• Endopelvic fascia (pubocervical and rectovaginal fascia) connect the uterus/vagina to pelvic sidewalls.

• Cystocele results from tear in pubocervical fascia. Anterior rectocele or enterocele results from tear in the rectovaginal fascia.

• Perineal body central tendon where the external anal sphincter, endopelvic fascia, urogenital diaphragm and puborectalis muscle insert. At the inferior-most aspect of the rectovaginal septum in women and posterior to the spongiosus and cavernosus bodies in men.