So in this next part of this tutorial, we'll be looking at the deep perineal pouch and
the perineal membrane.
Inferior to the pelvic diaphragm, you've got this membrane which is called the perineal
membrane.
You can see this triangularly-shaped structure here, which I've outlined in green.
This is a thick fascial structure which attaches along the pubic arch.
So you've got this attachment along the pubic arch here.
At the back, it's got this posterior border, which is free.
It's not attached to anything.
This membrane actually provides attachment for the roots of the external genitalia.
I'll come on to talk about this in another tutorial on the perineum.
But importantly, it's got these two holes to allow structures to pass from the pelvic
floor into the perineum.
This is a model of a woman, so you've got these two holes here.
Anteriorly, you've got the urethral orifice and behind it, you've got the vaginal orifice.
In males, obviously, you don't have this orifice for the vagina.
You've just got the anterior urethral orifice in males.
So if you remember, I mentioned the urogenital hiatus of the pelvic diaphragm, that u-shaped
defect.
Above the perineal membrane, you've got this urogenital hiatus.
If I just rotate the model anteriorly again, you can see that there's this little gap between
the anterior border of the perineal membrane and the pubic symphysis.
So you've got a little gap here.
If I rotate back to superior view, you can see the urogenital hiatus here and the parts
of the perineal membrane with the two orifices for the vagina and the urethra.
I've just added the female reproductive system in and you can see the vagina entering into
the pelvic cavity through this vaginal orifice in the perineal membrane.
With the urinary system added, you can see the bladder and you can see the urethra here.
So the last part of pelvic floor to mention is the deep perineal pouch.
The deep perineal pouch is this fascial capsule which lies above the perineal membrane.
This contains various layers of skeletal muscle which differ between men and women.
All the muscles in this compartment are innervated by the perineal branches of the pudendal nerve.
So what I'm going to do is I'm going to switch to a cross-section to try and illustrate the
deep perineal pouch.
What I've done here is taken a median sagittal section of this model.
If I just rotate inferiorly, you can see that I've sliced in half the perineal membrane.
If I just rotate around laterally, I'll show you what we're looking at.
So we've got the layer of levator ani muscles here, so the pelvic diaphragm above here superiorly.
And then just below it, we've got the perineal membrane.
So between the pelvic diaphragm muscles and the perineal membrane, you've got this deep
perineal pouch.
So it lies like this.
It's actually opened above.
So there's no layer separating the pelvic diaphragm muscles from the perineal pouch.
So you've got this fascial pouch, which I've drawn in green and it's opened superiorly.
So like I've said, you've got a few different structures within this pouch and they're innervated
by the perineal branches of the pudendal nerve and they're different in men and women.
So what I'm going to do is show you some of the structures that are within this perineal
pouch, this deep perineal pouch.
Back to the superior view of the pelvic, which you're familiar with, I'm just going to dissect
away the pelvic diaphragm muscles, so I've got rid of those muscles and we're looking
superiorly at the perineal membrane.
So the content of the pouch sits on top of this in this fascial pouch.
So remember, we're looking at a model of a woman, so we've got the vaginal opening here
and we've got the urethral opening anteriorly.
So first, we'll look at the muscles in female because they've got two more muscles than
men.
We've got this free border of the perineal membrane at the posterior aspect.
In the midline, we've got this little body called the perineal body, which is a fibromuscular
connective tissue node, which connects the structures of the perineum to the pelvic cavity
above, the pelvic floor above.
So the first muscle that we have is this deep transverse perineal muscle.
It attaches laterally on the ischiopubic ramus and it inserts onto this perineal body in
the midline.
So that's the deep transverse perineal muscle.
And then over here, you can see this little muscle here.
This is the external urethral sphincter.
This surrounds the proximal part of the urethra in women and the membranous part of the urethra
in males.
And then we've got two muscles which are unique to females.
So we've got the compressor urethrae.
And then we've got the sphincter urethrovaginalis.
So the compressor urethrae originates from the sides of the ischiopubic ramus.
And then it loops in like this and meets anteriorly to the urethra.
So you've got this compressor urethrae muscle and it meets anterior to the urethra.
This muscle aids the external urethral sphincter in closing off the urethra.
And then you've got this muscle called the sphincter urethrovaginalis.
As the name suggests, it forms this sphincter around the opening of the vagina in the perineal
membrane and it also blends with these fibers here.
So it surrounds the opening of the urethra as well, so urethrovaginalis.
This originates on the perineal body at the back.
I'm going to pass this forward surrounding the opening with the vagina and then it blends
anteriorly with the muscles surrounding the urethral opening in the perineal membrane.
So in men, you've just got the deep transverse perineal muscle and the external urethral
sphincter.
Something else to remember in males is that within this deep perineal pouch, you've also
got these glands called bulbourethral glands, which are also known as the glands of Cowper.
So they lie within the deep perineal pouch.