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  • Writer's pictureDanielle Ware

Anatomy - Everything you wanted to know about the pelvis but were too embarrassed to ask!

Updated: Apr 1, 2022


One thing we find ourselves talking about a lot is the anatomy of the pelvis. Unfortunately, there are still some myths and misconceptions about what is and is not normal for the genitals and reproductive organs. It's also not common knowledge what the pelvic floor muscles do. Today's blog aims to give an overview of the anatomy of the pelvis, genitalia, pelvic organs, and pelvic floor muscles.


There will be diagrams and descriptions of genitals here so this may not be a great post to read at work!


**Please note that in this blog we will discuss male and female anatomy for cisgender people. We want to acknowledge that this does differ for Intersex and Transgender people. **


Contents:



The Pelvis

https://commons.wikimedia.org/wiki/File:Blausen_0723_Pelvis.png#/media/File:Blausen_0723_Pelvis.png

The bony pelvis is a ring of bone, which contains the left and right "innominate" bones (which is 3 bones fused on each side), with the sacrum at the back, and the coccyx (tailbone) attached underneath the sacrum. Where the bones join at the front is called the pubic symphysis, the joints at the back between the innominate and sacral bones are called the sacroiliac joints. These joints are supported by very tough ligaments which make them incredibly stable joints, even during pregnancy!


https://anatomy.lexmedicus.com.au/collection/pelvis-hip


They also provide attachment points for a large number of important muscle groups: abs, back muscles, glutes, hamstrings, quads, adductors (inner thigh muscles), hip flexors (groin muscles,) and the pelvic floor. In short, it's a very important and very complex body area!

https://anatomy.lexmedicus.com.au/collection/pelvis-hip







Female Anatomy


Organs:

When we talk about "pelvic organs" we are referring to the 3 organs that sit within the bowl of the bony pelvis. From front to back, these are: the bladder, the uterus (womb) and the rectum. These organs each have an opening to the outside world. The bladder has the urethra (wee tube), the uterus has the vagina, and the rectum has the anus.


Before menopause, the thick walls of the vagina provide some support to the urethra and the rectum. The average length of the vagina can vary but is typically between 4-9cm (most are between 4.8-7.4cm), but this can increase during sexual arousal. The cervix often sits lower closer to a menstrual period, which can make the length of the vagina seem shorter.


Vulva:

The vulva refers to the whole outside genital area and includes the inner and outer labia, clitoris, opening of the urethra, and the opening of the vagina.

What diagrams can't show you is that there is a lot of variation between people. It is said that vulvas are like faces, in that each one is unique! Some have long labia minora, some have short ones, some clitorises are longer, some are completely covered by the clitoral hood, some labia are uneven... and all of these are normal(click to view "Labia Library" if you wish to see the variations of normal).


The back portion of the vaginal opening is where the hymen can be found. Anatomically speaking, it is a fold of tissue that sits towards the back of the opening, and typically doesn't cover the opening to the vagina in an adult.


The hymen should change shape with age, puberty, muscular factors, and physical activity. The current research also shows that the hymen can look the same whether or not someone has had sexual penetration, which means that the hymen cannot tell your partner or healthcare professional your sexual history.

The hymen is flexible tissue just like the rest of the vulva and vagina, and it can stretch to accommodate and tampon, a finger, a speculum, and even an erect penis. With enough arousal, good lubrication, and going slowly the first time you have vaginal penetration, you may have no bleeding and no pain.


We'll briefly mention here the part of the clitoris you can see externally is only a very small

portion of it. The outside part is called the glans clitoris and contains over 8,000 nerve endings (depending on the sources this is at least the same as, or possibly double the number of nerve endings found in a penis). But then the clitoris extends into the pelvis with an internal length of between 7-9cm.


The clitoris contains spongy tissue similar to a penis, and during sexual arousal this spongy tissue fills with blood, becoming erect and growing in size. These functions are sexual arousal, sexual pleasure, and orgasm. We'll talk more about this in a future blog on sexual function.


Pelvic Floor

The pelvic floor muscles are nearly identical between sexes, but the main difference is how they are arranged around the different openings. The pelvic floor in females has 3 openings for the urethra, vagina, and anus.

https://www.researchgate.net/figure/Anatomy-of-the-pelvic-floor-muscles-in-women-A-Superior-view-of-the-pelvic-floor-in-the_fig1_343120900

There are 2 layers of muscle: surface layer (B) and deep layer (A). This is helpful to know as

sometimes you can have issues with one or the other, or both!


All together as a group, they have a few functions including:

  • Controlling when you do and don't wee, poo, and pass gas

  • Supporting your organs

  • Working with your abs, back, and hips to support your trunk

  • Sexual arousal, sensation, and orgasm


The surface muscles play more of a role with sexual functions, but they also support the lower portion of the vagina and the urethra.


https://www.researchgate.net/figure/Anatomy-of-the-pelvic-floor-muscles-in-women-A-Superior-view-of-the-pelvic-floor-in-the_fig1_343120900

The deep muscles support the organs, control bladder and bowel, are active during sex and orgasm, and are important to support trunk and hip movements.


It's also worth knowing that the pelvic floor also incorporates some very strong ligaments (pictured above) and connective tissue which also support your organs. They may be stretched in someone with a prolapse, or in someone with endometriosis, there may be endometriosis lesions, scarring, or adhesions here.





Male Anatomy


Organs:

When we talk about "pelvic organs" for those assigned male, we are referring to the organs that sit within the bowl of the bony pelvis. These are: the bladder, the prostate, and the rectum. The bladder and prostate are connected to the outside world via the urethra (wee tube), and the rectum continues on into the anus.


The prostate is wrapped around the urethra, and part of the internal sphincter - or one of the muscles controlling the bladder. The role of the prostate is to produce the fluid part of semen that the sperm can travel through during ejaculation.


Genitals:

There are many articles written and questions asked on online forums about what is normal when it comes to male genitalia. The answer is that there is a lot of variation, each person's genitals are unique. Normal and healthy penises come in lots of different shapes, sizes, and lengths. The average penis is actually shorter than what pornography and other media say. The average length of an erect penis is between 12.9-13.9cm (or 5.1-5.5 inches), and a flaccid penis is on average between 7.5-10.7cm in length. While these numbers represent a large number of men, you can still be perfectly normal and have a measurement that is longer or shorter than these. The length of the penis can change after trauma or after surgery such as prostatectomy, but this is an important thing to discuss with your doctor as there is treatment available. If the shape of the penis changes, or your penis starts to bend or become painful then this is also worth discussing with your doctor as this is not normal and requires treatment.


The penis comprises the urethra (the tube that carries both urine and semen), spongy tissue surrounding the urethra, and two much larger columns of spongy tissue above. The 3 columns of spongy tissue fill with blood during sexual arousal to establish an erection. At the end of the penis is then the glans penis (often called the head of the penis) and underneath is the line of tissue called the frenulum. These two areas contain a high concentration of nerve endings which make them more sensitive during sexual arousal and stimulation. For those who are uncircumcised, the foreskin can vary in length and shape, but it should be able to retract (be pulled back) over the glans without pain. If this becomes painful or you cannot retract your foreskin you should speak with your doctor.


Pelvic Floor

The pelvic floor muscles are nearly identical between sexes, but the main difference is how they are arranged around the different openings. The pelvic floor in males has 2 openings for the urethra and anus.


There are 2 layers of muscle: surface layer and deep layer. This is helpful to know as

sometimes you can have issues with one or the other, or both!

https://pubs.rsna.org/doi/full/10.1148/rg.2019190064

All together as a group, they have a few functions including:

  • Controlling when you do and don't wee, poo, and pass gas

  • Working with your abs, back, and hips to support your trunk

  • Establishing and maintaining an erection

  • Propelling semen during ejaculation



The surface muscles sit over the base of the penis and in the perineum (that area behind the scrotum and before the anus). They play

https://pubs.rsna.org/doi/full/10.1148/rg.2019190064

more of a role with sexual functions, but they also provide some closure of the urethra which can help with bladder control and ensure no urine is left behind in the urethra after you've urinated.


The deep muscles support the organs, control bladder and bowel, are active during sex and orgasm, and are important to support the trunk and hip movements.




Intersex and Transgender


Intersex people make up about 1.7% of the population - which makes being intersex as common as having red hair! Intersex means that a person is born with some anatomy that would be called "male" and some that would be called "female." There are lots of variations in anatomy between intersex people.


Transgender means that a person's identity doesn't match the sex they were assigned at birth. Not all transgender people choose to undergo medical or surgical procedures as part of their transition. This means that some people who identify as male have genitals that textbooks label as "female." We also acknowledge that non-binary and agender people can come under the transgender umbrella.


As pelvic health physiotherapists, we treat each person with respect and will use your pronouns and anatomical terms that you feel comfortable with. We can help with pelvic health issues in any person, regardless of their anatomy or their gender identity.



Conclusion:


So to sum up, a lot is going on in the pelvis! Your Pelvic Health physiotherapist will be able to explain your condition as it relates to you, your history, your anatomy, and your lifestyle. We believe that knowledge is power, so we hope that the information in this blog helps you to put your condition into context and take better control of your own recovery!

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