Just below the pelvic diaphragm the urethra passes through the perineal membrane, which has been removed in this dissection.
The membranous urethra, which is here, is surrounded by the voluntary external urethral sphincter muscle, which is continuous with the levator prostatae.
Immediately beneath the pelvic floor the urethra enters the bulb of the penis. We'll follow its further course, later in this tape.
Now we'll look at the same area in the female. Let’s get oriented again. Here’s the pubic symphysis, here’s the coccyx. Here's the cut edge of the pelvic diaphragm. It’s being supported artificially on a wire frame. Here’s the vaginal opening, here’s the anus, and the external anal sphincter.
Here's the bladder, with the ureter entering here. Immediately behind the bladder is the vagina, and above it the uterus, very small in this specimen. We’ve removed the broad ligament, which was here.
Directly behind the vagina is the rectum. The female urethra is quite short. This is the urethra, surrounded by the external urethral sphincter muscle. The female urethra ends by entering the vestibule of the vagina.
We can see the urethra better in this isolated specimen. Here's the bladder, here's the vagina. Here's the entrance to the vagina: the vestibule. The urethra starts here, and runs parallel to the vagina. It's surrounded by the external urethral sphincter muscle.
The vagina and urethra pass through the pelvic diaphragm. We've left a fringe of the pelvic diaphragm intact here: it's attached both to the urethra, and the vagina.
To see the urethra, we'll look at a specimen that's been divided in the midline. Here's the lower part of the vagina, here's the vaginal vestibule. Here's the urethra. Here's the external urethral sphincter muscle, here's the internal urethral meatus, here's the external meatus. Here's the external urethral meatus seen from below, opening into the vestibule of the vagina.
We'll see more of the male and female urethra in the following section, on the reproductive system.