Posts Tagged ‘scrotum’

Men Are From Mars, Women From Venus, But There’s Not Much Difference Between A Vagina And A Penis

December 10, 2016

Andrew Siegel MD 12/10/2016

What is it that most distinguishes a male from a female? The obvious answer is the genitals, with the penis/scrotum having a vastly different appearance from a vagina/vulva.  Despite the male and female genitals being the feature that most characterizes the difference between a male and female, there are striking similarities. The genitals of both sexes are biologically homologous– similar in structure and having a common embryological origin–with development into male versus female based simply on the hormonal environment at the time of development.  Today’s entry discusses the similarities (as opposed to the differences) between the genitals and the “homologues,” the specific anatomical structures that are of common embryological origin and are more alike than are commonly recognized. 

Whether one develops a penis or a vagina is determined at the moment the sperm penetrates the egg. The egg contains an X chromosome and the sperm either an X or Y chromosome. When the coupling results in an XX, the blueprint for female development is established; when the coupling results in an XY, the blueprint for male development is established. The bottom line is that the father determines the sex of the child.

Several weeks later, when the fertilized egg has turned into an embryo, the external genitals are identical. Female genitals are the “default” model, which will remain female, absent the presence of the male hormone testosterone (T). T is activated to dihydrotestosterone (DHT) that causes conversion of what would be a vulva and vagina into a penis and scrotum. Biochemical magic! The bottom line is that the developing embryo will remain female unless T/DHT are available to masculinize the external genitals.

In the young embryo there are three key genital structures: the “tubercle,” the “folds” and the “swellings.” In the absence of T/DHT, the genital tubercle (a midline swelling) develops into a clitoris. The urogenital folds (two vertically-oriented folds of tissue below the genital tubercle) become labia minora (inner lips). The labio-scrotal swellings (two vertically-oriented bulges outside the urogenital folds) fuse to become labia majora (outer lips). In the presence of T/DHT the genital tubercle morphs into a penis, the urogenital folds become the urethra and part of the penile shaft and the labio-scrotal swellings fuse to become a scrotum.

Genital Homologues

The penis is the homologue of the clitoris. Both structures are highly sensitive organs with a tremendous concentration of nerve fibers and contain erectile tissue (corpora) that enables them to expand in size and rigidity with stimulation. Both the penis and clitoris have a head (glans) and shaft and deep internal roots. Both are covered with a layer of skin that can be pulled back to expose the underlying anatomy. In the male this is referred to as the foreskin, which is the homologue of the female clitoral hood.

penile-clitoral_structure

Comparison of penis (left) and clitoris (right)–note similar shape and internal structure, Attribution: Esseh, Wikipedia Commons

The male scrotal sac is the homologue of the female labia majora. The raphe (the seam that runs vertically up the perineum, scrotum and penis) is the homologue of the pudendal cleft (the slit between the labia) in the female.

vulva_vs_scrotum

 

Comparison of vulva (left) and scrotum (right); note similarity of outer labia to scrotum and female pudendal cleft to male raphe,  by Richiex (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)%5D, via Wikimedia Commons

The male prostate gland is the homologue of the female Skene’s glands. Both produce fluid that is released at the time of sexual climax. The male Cowper’s glands are the homologue of the female Bartholin’s glands, both of which secrete fluid at the time of sexual stimulation, pre-ejaculate fluid in the male and vaginal lubrication fluid in the female.

 

male_anatomy_en-svg

Male anatomy, note prostate gland and Cowper’s glands, by Male_anatomy.png: alt.sex FAQ derivative work: Tsaitgaist (Male_anatomy.png) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)%5D, via Wikimedia Commons

skenes_gland-svenska

Note Skene’s gland and Bartholin’s glands openings below and to side of urethra and vagina respectively, by Nicholasolan (Skenes gland.jpg) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)%5D, via Wikimedia Commons

Bottom Line: As different as female and male anatomy are, so they are similar.  The study of comparative genital anatomy and embryological origin is fascinating.  Next week’s entry addresses when this process of differentiation into male versus female goes awry, leading to “ambiguous” genitalia, and how the study of one such particular genetic defect led to the creation of a billion dollar blockbuster drug in common use for purposes of shrinking enlarged prostates and growing hair in men with male pattern baldness.   

Wishing you the best of health,

2014-04-23 20:16:29

www.AndrewSiegelMD.com

A new blog is posted every week. To receive the blogs in the in box of your email go to the following link and click on “email subscription”:  www.HealthDoc13.WordPress.com

Andrew Siegel MD practices in Maywood, NJ.  He is board-certified in both urology and female pelvic medicine/reconstructive surgery and is Assistant Clinical Professor of Surgery at the Rutgers-New Jersey Medical School and attending urologist at Hackensack University Medical Center. He is a Castle Connolly Top Doctor New York Metro area and Top Doctor New Jersey.

Dr. Siegel is the author ofTHE KEGEL FIX: Recharging Female Pelvic, Sexual and Urinary Health (www.TheKegelFix.com) and MALE PELVIC FITNESS: Optimizing Sexual & Urinary Health (www.MalePelvicFitness.com). 

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Man Kegel Exercises

February 22, 2014

Blog # 142

As a urologist, I have expertise in both male and female pelvic health as opposed to gynecologists who treat only women. When I reflected on the similarities and differences of the male and female pelvis, genitalia and pelvic floor, I came to some important conclusions. It occurred to me that in terms of development, the male and female genitalia are incredibly similar with respect to their embryological origin. Additionally, the pelvic floor muscles (PFM) are virtually identical in both genders. Exercises of these pelvic floor muscles for purposes of improving sexuality, urinary control and pelvic support are widely known and acknowledged in the female population; in fact, women are instructed to do these “Kegel” exercises during and after pregnancy. So, why not for men?

Hmmmm…identical origin of genital tissues, the same exact muscles, documented effectiveness of these exercises for women’s pelvic health…what’s the missing link? The missing link is that if they are so beneficial for females, why have they virtually been ignored when it comes to the male population? Hey: What’s good for the goose is good for the gander. More specifically, what is good for the female goose is equally good for the male goose. PFM exercises are gender-neutral, having the same meaningful potential in males that they have proven to have in females but for some reason, have been largely neglected and remain an unexploited and powerful resource.

In the 1940s, Dr. Kegel—a gynecologist from Los Angeles—popularized pelvic floor muscle (PFM) exercises in females in order to help improve sexual and urinary health after childbirth. I think it is fair to state that most adult women have heard of and many have practiced these exercises, known as “Kegels.”  In brief, when a woman does a Kegel contraction, she voluntarily contracts the muscles that surround the urethra, vagina, and rectum. As a result, the urethra gets pinched, the vagina tightens up, and the rectum gets squeezed.

Kegel pelvic floor muscle exercises are by no means a new concept, Hippocrates and Galen having described it in Ancient Greece and Rome respectively, where they were performed in the baths and gymnasiums. Strengthening these muscles was thought to promote general and sexual health, spirituality, and longevity

Men have the very same pelvic floor muscles that women do and an equivalent capacity for exercising them, with a parallel benefit and advantage to urinary and sexual health. Nonetheless, the male PFM have yet to receive the recognition that the female PFM have, although from a functional standpoint are of vital importance, certainly as critical to male genital-urinary health as they are to female genital-urinary health. When a man contracts his pelvic floor muscles, he voluntarily tightens the muscles that surround the urethra and rectum, which enables him to stop his urinary stream and tighten his anus. Under the circumstances of having an erection, when the PFM are engaged, the penis will lift skywards towards the heavens. Unfortunately, however, most men are unfamiliar with pelvic floor muscle exercises and it is the rare man who has performed them. Even many physicians are unaware of the pelvic floor muscles and their potential benefits for men.

In terms of anatomy, the male and female external genitalia at the earliest stages of embryological development are identical. That is, one and the same, duplicate, a carbon copy of each other. No “his” and “hers,” only “hers” and “hers.” Add testosterone (the male sex hormone), to the recipe and presto, the primitive male genitals transform into a penis and scrotum. In the presence of testosterone the genital tubercle (a midline swelling) becomes the penile shaft and head; the urogenital folds (two vertically-oriented folds of tissue below the genital tubercle) fuse and become the urethra and part of the penile shaft; and the labio-scrotal swellings (two vertically-oriented bulges outside the urogenital folds) fuse and become the scrotum. In the female embryo, the absence of testosterone causes the genital tubercle to become the clitoris, the urogenital folds to become the inner lips (labia minora), and the labio-scrotal swellings to become the outer lips (labia majora).

Essentially then, the penis and the clitoris are the same structure, as are the scrotum and outer labia.  How fascinating it is that female external genitalia are the “default” model.  In other words, female external genitalia form in the absence of testosterone, and not in the active presence of female hormones.

Similarly, the PFM are virtually identical in both genders, as can be clearly seen in the images that follow (credit to Dr. Henry Gray, Gray’s Anatomy of the Human Body, 20th edition, originally published in 1918; public domain).  Compare the bulbocavernosus muscle in the male with that of the female and the ischiocavernosus muscle in the male and the female. The only real difference is that the BC muscle in the female is split around the vagina.

ImageImageImageImage

In summary, we have identical origin of genital tissues, same exact muscles, and well-documented effectiveness of these exercises for women’s pelvic health. So why do we never hear about PFM exercises for male pelvic health? If the genital and PFM anatomy is virtually “the same” in both genders, as is the supportive, sphincter and sexual functions of the PFM, then why should PFM exercises be any less beneficial for males than females? The bottom line is that pelvic floor muscle exercises in the male have the same meaningful potential that they have proven to have in females, but for some reason, have been ignored, neglected and remain an untapped yet valuable resource.

My objective is to bring to the forefront an awareness of the male pelvic floor muscles and an understanding of the numerous benefits of tapping into their capacity for optimizing and improving sexual and urinary function. My ultimate goal is to help male pelvic fitness achieve the same traction and status as female pelvic fitness has, as did Dr. Arnold Kegel for females. To be continued…

Andrew Siegel, M.D.

Much of this material was excerpted from Male Pelvic Fitness: Optimizing Sexual and Urinary Health; in press and available in e-book and paperback formats in March 2014. www.MalePelvicFitness.com

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