Andrew Siegel, MD 3/12/2016
One of the advantages of the specialty of urology is that it encompasses patients of both genders, unlike gynecology, which strictly involves females. Since I am board certified in Urology as well as in Female Pelvic Medicine, my practice allows me to have an equal balance of male and female patients. This gives me the opportunity to appreciate comparative male and female pelvic anatomy and function, which in reality are remarkably similar–a fact that may surprise you.
A Few Brief Words on the Embryology of the Genitals.
Who Knew? Female and male external genitals are remarkably similar. In fact, in the first few weeks of existence as an embryo, the external genitals are identical.
The female external genitals are the “default” model, which will remain female in the absence of the male hormone testosterone. In this circumstance, the genital tubercle (a midline swelling) becomes the clitoris; the urogenital folds (two vertically-oriented folds of tissue below the genital tubercle) become the labia minora (inner lips); and the labio-scrotal swellings (two vertically-oriented bulges outside the urogenital folds) fuse to become the labia majora (outer lips).
(Comparison of genital anatomy, 1918 Gray’s Anatomy, Dr. Henry Gray, public domain)
In the presence of testosterone, the genital tubercle morphs into the penis; the urogenital folds fuse and become the urethra and part of the shaft of the penis; and the labio-scrotal swellings fuse to become the scrotal sac. So, the clitoris and the penis are essentially the same structure, as are the outer labia and the scrotum.
Ejaculation is the expulsion of fluids at the time of sexual climax. The word “ejaculation” derives from ex, meaning out and jaculari, meaning to throw, shoot, hurl, cast. We are all familiar with male ejaculation, an event that is obvious and well understood and well studied. However, female ejaculation is a mysterious phenomenon and a curiosity to many and remains poorly understood and studied.
Men often “dribble” before they “shoot.” The bulbo-urethral glands, a.k.a. Cowper’s glands, are paired, pea-sized structures whose ducts drain into the urethra (urinary channel). During sexual arousal, these glands produce a sticky, clear fluid that provides lubrication to the urethra. (These glands are the male versions of Bartholin’s glands in the female, discussed below).
Once a threshold of sexual stimulation is surpassed, men reach the “point of no return,” in which ejaculation becomes inevitable. Secretions from the prostate gland, seminal vesicles, epididymis, and vas deferens are deposited into the urethra within the prostate gland. Shortly thereafter, the bladder neck pinches closed while the prostate and seminal vesicles contract and the pelvic floor muscles (the bulbocavernosus and ischiocavernosus) spasm rhythmically, sending wave-like contractions rippling down the urethra to forcibly propel the semen out in a pulsatile and explosive eruption. Ejaculation is the physical act of expulsion of the semen, whereas orgasm is the intense emotional excitement and climax, the blissful emotions that accompany ejaculation.
(Male Internal Sexual Anatomy, permission CC BY-SA 3.0, created 18 April 2009)
What’s in the Ejaculate?
Less than 5% of the volume is sperm and the other 95+% is a cocktail of genital secretions that provides nourishment, support and chemical safekeeping for sperm. About 70% of the volume comes from the seminal vesicles, which secrete a thick, viscous fluid and 25% from the prostate gland, which produces a milky-white fluid. A negligible amount is from the bulbo-urethral glands, which release a clear viscous fluid that has a lubrication function. The average ejaculate volume is 2-5 milliliters (one teaspoon is the equivalent of 5 milliliters).
Who Knew? While a huge ejaculatory load sounds desirable, in reality it is correlated with having fertility issues. The sperm can literally “drown” in the excess seminal fluid.
This is a much less familiar subject than male ejaculation and a curiosity to many. Only a small percentage of women are capable of expelling fluid at the time of sexual climax.
The nature of this fluid is controversial, thought by some to be excessive vaginal lubrication and others to be glandular secretions. Although the volume of ejaculated fluid is typically small, there are certain women who ejaculate very large volumes of fluid at climax. Expulsion of fluid at climax may come from four possible sources: vaginal secretions; Bartholin’s glands; Skene’s glands; and the urinary bladder.
(Skene’s and Bartholin’s Glands, created 22 January 2007, original uploader Nicholasolan en.wikipedia, Permission: CC-BY-SA-2.5, 2.0, 1.0; GFDL-WITH-DISCLAIMERS; CC-BY-S)
During female arousal and sexual stimulation, the vaginal walls lubricate with a “sweating-like” reaction as a result of the increased blood flow to the genitals and pelvic blood congestion, creating a slippery and glistening film. The amount of this lubrication is highly variable. Some women with female ejaculation can release some of this fluid at the time of climax by virtue of powerful contractions of the vaginal and pelvic floor muscles.
Bartholin’s glands are paired, pea-size glands that drain just below and to each side of the vaginal opening. They are the female versions of the male bulbo-urethral glands and during sexual arousal they secrete small drops of fluid, resulting in moistening of the opening of the vagina.
Skene’s glands (para-urethral glands) are paired glands that drain just above and to each side of the urethral opening. They are the female homologue of the male prostate gland and secrete fluid with arousal.
Scientific studies have shown that those women who are capable of ejaculating very large volumes are actually having urinary incontinence due to an involuntary contraction of the urinary bladder that accompanies orgasm. This is often referred to as “squirting.”
Bottom Line: In the animal kingdom (including human beings), sex is a clever “bait and switch” scheme. In the seeming pursuit of a feel-good activity, in reality—determined by nature’s evolutionary sleight of hand—participants are hoodwinked into reproducing. The ultimate goal of the reproductive process is the fusion of genetic material from two individuals to perpetuate the species.
The penis functions as a “pistol” to place DNA deeply into the female’s reproductive tract with ejaculation a necessity for the process. Similarly, the female genitals need to be sufficiently lubricated to optimize this process and the combination of vaginal lubrication from enhanced blood flow contributed to by Skene’s and Bartholin’s secretions will optimize nature’s ultimate goal.
Wishing you the best of health,
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
Author of Male Pelvic Fitness: Optimizing Sexual and Urinary Health: available in e-book (Amazon Kindle, Apple iBooks, Barnes & Noble Nook, Kobo) and paperback: www.MalePelvicFitness.com. In the works is The Kegel Fix: Recharging Female Pelvic, Sexual and Urinary Health.
Co-creator of Private Gym and PelvicRx, comprehensive, interactive, FDA-registered follow-along male pelvic floor muscle training programs. Built upon the foundational work of Dr. Arnold Kegel, these programs empower men to increase pelvic floor muscle strength, tone, power, and endurance: www.PrivateGym.com or Amazon.
Pelvic Rx can be obtained at http://www.UrologyHealthStore.com, an online store that is home to quality urology products for men and women. Use code UROLOGY10 at check out for 10% discount.
Tags: Andrew Siegel MD, Bartholin's glands, Cowper's glands, ejaculation, lubrication, male pelvic fitness, orgasm, penis, prostate gland, reproduction, semen, seminal vesicles, sexual intercourse, Skene's glands, urology, vagina, vas deferens