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Let's talk about the membranous urethra,

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which is one of the components, the inferior

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component, of the posterior urethra, which

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means there's got to be an anterior urethra,

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which begins at the bulb and goes into

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the penis and then the external meatus.

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Set that aside again and focus on the membranous

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urethra, which is the continuation or lies

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just inferior to the lower prostatic urethra.

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And here it is in the axial projection.

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These are all 2D, 3-millimeter, heavily

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water-weighted T2 fast spin echo images.

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So in the coronal projection, this is a

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direct coronal orthogonal, sagittal, and axial.

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We see the urethra coming down towards this dark

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U-shaped area, more inferiorly, between these

0:51

two muscle bellies, the membranous urethra.

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Now, the membranous urethra in the axial

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projection is only about one centimeter long.

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So, if you're using three-millimeter cuts, you're

1:04

only going to see it for three slices in total.

1:08

In the membranous segment is the external

1:10

sphincter and also two paired Cowper's glands.

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Can you see the Cowper's glands?

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Sometimes you can.

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For instance, on this coronal image, there is

1:20

the right Cowper's gland opening just adjacent

1:24

to the membranous urethra on the right.

1:27

And it does communicate with

1:28

the urethra, although we don't have the

1:30

resolution to see that communication.

1:34

In the axial projection, I'm gonna make

1:35

it a little bigger. In the membranous

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urethra, you can divide it up into a

1:41

brighter central area, which is white.

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Now, all you have to remember is white,

1:46

dark, white, dark for the zones

1:50

down in the membranous urethra.

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So white in the middle, central zone.

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Then you have an inner area that you

1:57

can barely see, it's pretty thin, dark.

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Then you have a middle area which is

2:03

a little bit brighter and thicker.

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Brighter and then dark around the periphery.

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So white, dark, white, dark.

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Central, inner, middle, outer.

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And that, my friends, is the membranous urethra.