Welcome to the middle.
The little yellow dot below represents the perineum, or perineal body. I like to think of as Grand Central Station - lots of things park here from many different places (bulbo, STP and EAS…as well as DPT which we’ll talk about next post). Because of this, the perineal body has fibers arranged in many different areas which makes it super strong and a perfect place for the pressures pelvic and abdominal cavities to bounce on as we inhale and exhale. It is the keystone of the dome of the pelvic floor.
As with layer one, these muscles are innervated by branches of the pudendal nerve that exit the spine from S2 - S4.
Deep Transverse Perineum
Originates from the inner rim of the inferior ischial ramus
Inserts at a midline tendinous raphe and the perineal body
It stabilizes the perineal body, stabilizes the pelvic floor
Sphincter Urethrovaginalis (Women)
Originates from the perineal body
Inserts in a loop around the anterior vagina
Helps to close the vagina and the urethra
External Urethral Sphincter
Originates from the ischiopubic ramus
Inserts in a loop around the urethra
Helps close the urethra
Pelvic Floor Layers, Side View
Pelvic Floor Layers, View from Above (looking down, from the diaphragm into the pelvic outlet)
Pelvic Floor Layers, View from Below (looking up at the pelvic floor, from between the legs)