 The pelvis is a complex piece of anatomy, so let's begin by taking a moment to get our bearings. The perineum lies at the bottom of the pelvis. It is the space between the thighs encompassing anus and genitals. It is a diamond shaped space. The corners of the diamond are the coccyx, pubic symphysis, and two ischial tuberosities. The ceiling of the space is the pelvic floor muscles. The pelvic floor muscles, or levitore ani, are shaped like a bowl. So the ceiling of the space is partly convex. The walls are the ischial pubic ramai, the sacro tuberous ligament, which are the boundaries of the pelvic outlet. The diamond's anterior half is known as the urogenital triangle. The posterior half, the anal triangle. In a standing position, the urogenital triangle roughly conforms to the horizontal plane. The anal triangle is on an upward tilt, around 30 degrees from horizontal. To bring some perspective, here's the femur, a rough approximation of the coronal plane. Returning now to an inferior view. The urogenital triangle contains a fibrous sheet called the perineal membrane, oriented like so. The perineal membrane has upturned anterior and posterior edges and collects within it a space known as the deep perineal pouch. The ischial anal fossey partially occupy the space between this pouch and the pelvic floor muscles. The deep perineal pouch is thus a very shallow space. All of this in blue, ischial anal fossey, and the space contained by and just deep to the perineal membrane, coloured in purple, that's the deep perineal pouch. It contains within it a number of muscles, including the external urethral sphincter. In the female sex, the pouch includes two holes for vagina and urethra. These are allowed passage through the levator anion muscles in this U-shaped space known as the urogenital hiatus. Just deep to the skin is a membranous layer of superficial fascia known as collies fascia. And between the perineal membrane and the relevant part of collies fascia lies the superficial perineal pouch. This pouch contains the bulbo spongiosis, ischiocavenosis, and superficial transverse perineal muscles. It also contains various erectile tissue of the penis and clitoris, plus the continuation of the urethra and vagina. So that's the superficial and deep perineal pouches. The perineal membrane has a free posterior border. In the centre of this posterior border and of the diamond shaped perineum at large, lies the perineal body. Fibromuscular meeting point for many structures of the perineum. Many of the muscles we've mentioned so far converge here. Posteria and superior to that is the anal sphincter muscles, the centerpiece of the anal triangle. Let's go back and review the most important points now. The perineum is a 3D space with the pelvic floor muscles as its ceiling. The space is divided into the urogenital triangle anteriorly and anal triangle posteriorly. There are two perineal pouches, superficial and deep, both in the urogenital triangle and separated by the perineal membrane. That's it for now. Hit subscribe if you liked this video. Thanks for watching and we will see you next time.