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Female Urethral Sphincters! [Oct. 24th, 2008|07:43 pm]
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[sonrosado]
How many urethral sphincters are there in the female, one or two?

In Moore & Dalley's Clinically Oriented Anatomy 5th edition p.395 it mentions:

"toward the neck of the male bladder the muscle fibres form the involuntary internal urethral sphincter..." and then goes on to describe how they behave during ejaculation.

No mention of an internal urethral sphincter in females, only an orifice.

thanks in advance any assistance
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[User Picture]From: sonrosado
2008-10-24 07:00 pm (UTC)

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can you give me a reference for that? (thank you!)
[User Picture]From: jerseyjess
2008-10-24 08:17 pm (UTC)

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Yeah, that was what I thought too. Try looking it up in Netter's? There should be a picture in there.
[User Picture]From: sonrosado
2008-10-25 05:25 am (UTC)

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Which book do you mean by Netter's? (I'm in the UK & we call everything differently!)

Thanks for your input though
[User Picture]From: jerseyjess
2008-10-25 11:20 am (UTC)

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Sorry, I was referring to Netter's Atlas of Human Anatomy. It was the book we used in my class instead of Gray's Anatomy.
[User Picture]From: changalicious
2008-10-24 08:56 pm (UTC)

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Two. No reference, though, but I am pretty sure of this. Wikipedia?
[User Picture]From: sonrosado
2008-10-24 09:12 pm (UTC)

Big Daddy Gray's Anatomy 39th Edition (not Gray's for students!)

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on p.1299

"The smooth muscle coat extends throughout the length of the urethra and consists of slender muscle bundles, the majority of which are arranged smoothly and longitudinally.
A few circularly arranged muscle fibres occur in the outer aspct of the non-striated muscle layer and intermingle with the skeletal muscle fibres forming the inner part of the external urethral sphincter.

Proximally the urethral smooth muscle extends as far as the bladder neck where it is replaced by fascicles of detrusor smooth muscle.
this region in the female lacks a well-defined circular smooth muscle component comparable with the preprostatic sphincter of the male"


It then goes on to say "in the absence of an anatomical sphincter continence of the female bladder neck"

to me this suggests the female doesn't have an internal urethral sphincter?


[User Picture]From: 8wishes
2008-10-25 12:08 am (UTC)

Re: Big Daddy Gray's Anatomy 39th Edition (not Gray's for students!)

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I remember learning in first-year anatomy that females don't have internal sphincters, and that's partly the reason why it's easier for women to have stress incontinence. It's been a couple of years and I have no references, so I could be wrong about it.
[User Picture]From: 8wishes
2008-10-25 03:25 am (UTC)

Re: Big Daddy Gray's Anatomy 39th Edition (not Gray's for students!)

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So I just went to look it up on Google because this was kind of bothering me, especially since everyone else said females have both internal and external. Under the Google book entry for The Urinary Sphincter, it says: The female continence mechanism is different from its male counterpart. A physiological internal sphincter is not present. I went to Amazon.com and found that quote on page 192. Not sure if this is the authority on the topic, but there's a reference for you.
From: (Anonymous)
2008-10-25 05:23 am (UTC)

Re: Big Daddy Gray's Anatomy 39th Edition (not Gray's for students!)

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Thanks, thats really helpful.

big daddy gray's mentions 'sphincter muscles' so this probably the autonomically involuntary innervated part.. not an actual internal urethral sphincter but for the purposes of most medical curricula one could get away with saying females have two (i imagine)
[User Picture]From: maribella_ella
2008-10-24 09:58 pm (UTC)

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I have an anatomy text from undergrad (Human Anatomy 4th edition, by Marieb, Mallatt, and Wilhelm) that shows a picture of both male and female urinary tract, each with both an internal and external sphincter. It doesn't say it in the text, so I can't quote that for you, but the figure is clear that females have two sphincters.
[User Picture]From: sonrosado
2008-10-25 05:22 am (UTC)

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Thank you.

From big Daddy Gray's I get the impression females do not have an internal urethral sphincter but do have 'sphincter muscles' (but not a well defined anatomical sphincter) which are autonomically innervated. For the purposes of most medical curriculums vs. clinical anatomists saying they have two is probably OK..
Just the textbook I was reading had me so confused!
[User Picture]From: meran12345
2008-10-25 01:13 am (UTC)

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my GOD i'm so glad i don't have to go through anatomy again. SO GLAD.