Fembryology Part 1: Mars and Venus (A Discussion of Sexual Development)

By Elisothel (Also posted at feministmormonhousewives.org)
(Admin note: We have been given permission to re-post this series about gender development. This was written from a feminist perspective, but these issues of gender are also relevant to LGBT people, particularly trans mormons, and this kind of education is basic to understanding the meaning of gender in order to have a reasonable and informed discussion about such concepts as eternal gender, gender binary, gender equality and any issue that has gender requirements within Mormonism such as eternal marriage)

Girl Underwear  boy underwear


(Note:  I originally composed this post with not just diagrams but also photos – if you are interested in seeing actual photographs alongside the diagrams, you can access that draft HERE. The page is password protected – type in marsandvenus to get access

“Women are concave.  We are mysteries even to ourselves.”  – Ina May Gaskin

Remember 8th grade biology when you learned about human reproduction and saw that childbirth film designed to scare you away from teen sex?  Maybe getting this anatomical scoop on the birds and bees empowered you to think you knew it all (“That’s where babies come from!”).  But 8th grade science probably never got to Embryology – the process of where babies really come from, that story of how a fertilized egg turns into a human…and as far as I can tell our Church hasn’t gotten around to it either.    Oh yes, our Church has discussed evolution, the “Origin of Man”, and the rules surrounding sexual morality, but nowhere do we address that fundamental physicality that informs our existence:  our genitals.  Where do they come from?  Why are they here?  And where are they going?

At first glance it hardly appears that understanding our genitals would impact our understanding of the gospel.  But our biology defines us:  our physical needs, limitations, senses, and even just our mortal propensities to live and die all directly speak to comprehending and navigating the physical and metaphysical worlds.  The unfolding of human development was not understood for many millennia, and Christian religious discourse developed before the full facts were known.

I have prepared a series of posts that will be posted weekly over the coming months, in which we will explore how our physical and embodied reality informs our identities, how it makes a case for inherent human equality across genders, and how it informs our LDS theology.

Deep within ourselves lie answers – or at the very least some very poignant questions – concerning our origins and destinies.  Consider learning something new about yourself.  Here we go, and remember my friends, science isn’t pornography, nor is it politics.

(PLEASE NOTE There are images of genitals below, so DON’T SCROLL DOWN if you don’t want to look at diagrams of genitalia!)

After fertilization, the egg undergoes multiple divisions after which little cells line up in layers to form some early tissues.  The systems of the baby’s body are rudimentary and organizing.  This is true of the sexual organs as well.  Up until 6-8 weeks genital development is exactly the same for boys and for girls. That is, even if a boy has a Y chromosome at a cellular level and a girl has an X, they will both be structurally indistinguishable during the first 6-8 weeks.  Looking at the sex organs you would simply see a series of “urogenital folds” that will develop differently depending on the presence or absence of testosterone.

Here’s a picture of the structure – this will develop into EITHER a boy or a girl:


At this “biopotential stage,” girls and boys are structurally the same.  The sex, while chromosomally determined, is NOT yet structurally determined. Thus the baby is structurally designated as “indifferent”, not male or female.

I have heard people say, and oh how we’ve hashed it out, that “we all start as female, and with testosterone boys become male”.   No my friends, the sex of an embryo at 6-8 weeks is “indifferent”, it does not have a vagina, ovaries, or a uterus so it is NOT female.  The lack of a penis doth not a woman make.  However, the default developmental path is female:  without testosterone, the baby will be a girl regardless of its chromosomes. By the end of the 6-8 weeks the baby’s body is primed to develop distinguishing genital characteristics.

In the male, the tissues that will become the gonads (sperm factories) descend outward, with the labio-scrotal swelling fusing as the scrotum, the testes inhabiting the scrotum.

In the female, the tissue that will become the gonads (egg factories) will ascend upward into the body.  The labio-scrotal swelling will not fuse but remain apart as an opening, except at the perineum, which will fuse.

side by side

The male genitals move outside the body and fuse together.  The female genitals move inside the body and stay separated.  However, the gonadal systems are opposite:  The tubing for the male remains separate, and the tubing in the female fuses and swells into the uterus and vagina.


Because their parts are primarily external, guys experience their genitals in a far more tangible way:  they can see, handle, and observe their varied responses several times every day, just by going to the bathroom or changing their clothes.  Women rarely have this opportunity, especially since the Church – and society in general – discourages women from engaging in any kind of self-exploration.  We all know much more about male parts and function than female, because the female universe is hidden.

Despite the enormous differences between these two internal structures, each sex has residual tissues of the other.

Outies and Innies (and I don’t mean bellybuttons)

The hormones stimulated by genetic factors tell the parts how to develop, but both male and female have essentially the same tissues, with similar functions, in different forms.


Here’s a video that shows the above-illustrated process for girls:


Here’s a video that shows the above-illustrated process for boys:


The urogenital fold will close fully on the male, making the scrotum and penis.  The line where they fuse can be seen running up the center of the scrotum and penis, (look and see, guys, that line along the penis is where you used to be “open” just like a girl) known as the raphe.  The urogenital fold will only close partially on a female at the perineum between the vaginal opening and anus.  Here are photos of both the penile and vulvar raphes, and an illustration to see how each is formed in parallel:




The parallel but-not-quite-the-same processes that created the raphes, gonads, and external genitalia are all examples of homologues – the mature representations of those tissues that males and females once each had in common.  You can find a more comprehensive list of homologues here. Besides the already mentioned homologues of testes/ovaries and labia/scrotum, penile/vulvar raphes, here is a short treatment of other notable sexually dimorphic homologues:

Hood & Foreskin

Clitoral Hood


In the above image, 1 and 3 point to the tip (glans) of the clitoris, 2 is the clitoral hood, and 4 is the labia.  The male homologue to the clitoral hood is the foreskin:

Fembryology 12

Breasts & Chests

Men have nipples because at the indifferent state, the embryo had the potential to develop mammary (lactating breast) tissue.  As the boy became more differentiated this was de-emphasized, but the nipples still remain in the mature male as a trace indication of the body’s potential to develop along female lines. (I assume most readers are familiar with the difference between male and female chests, and while I did consider posting pictures, it seemed to sexualize the post way more than showing genitalia does – go figure!  So I refer you to you your memory for the difference).

Uterus/Guys don’t have one…right?

Fembryology13     Fembryology14

The indifferent embryo has a structure called the mullerian duct, which in a girl becomes the uterus.  In a boy, the mullerian duct becomes the prostatic utricle (also known as the vagina masculina, a duct that doesn’t lead anywhere). Look at the above picture of the prostate and find the label pointing to the prostatic utricle!

Clitoris & Penis

So let’s talk about the penis.  Boys have one, girls don’t, so guys have something the ladies don’t, right?  No, the penile structures have female homologues that also exist in parallel.  The penis tip is congruous to the tip of the clitoris, which most people know.  But the penile shaft, formed from the “indifferent” Genital Tubercle, has a parallel structure in women, we just don’t ever talk about it:  the Clitoris.  Wait, I just said that right? But it’s not just the little button you know about (the glans); here’s a picture of the whole thing:


That thing that looks like a bird, that’s the whole clitoris, and from wingtip to wingtip it is about 8 inches long (the width of a regular piece of typing paper is 8.5 inches).  From front to back, about 4-5 inches.

Fembryology15     bulb of penis

Like the labia, the tissues that make up the clitoris – structures parallel to the penis – DID NOT FUSE into a continuous shaft during embryonic development– it is fused only at one end and extends on either side of the vagina …but though it doesn’t look exactly the same as a penis (though the similarity IS striking), the male and female structures are congruous.

Those huge things underneath the clitoris, the “bulbs of vestibule”, that surround the vaginal walls – that is erectile tissue my friends.  And the male homologue, the bulb of penis, is much smaller than the woman’s.  So the guys get a larger shaft organ, and the ladies a larger bulb organ.  It’s a matter of emphasis.

Here’s the clitoris, and what happens to it when a woman is sexually aroused (TURN DOWN YOUR SOUND – the scientific narration is loud – and click the link):

Push here to start the video of what happens to the clitoris when aroused!

If you didn’t know that was a clitoris, what would you think it was?  So much for penis envy!

Ok – so what?

The wondrous thing out embryology is that it shows us how alike we are, where the differences come from, and that the differences are not a matter of “I have this and you don’t,” but more a matter of “we both have the tissues of the other, manifested in different ways.  Deep down, I have what you have.”   Embryology offers a possible answer to the question of whether men and women are different beings or simply parallel versions of the same being.

Embryology shows us that we had a potential to do what we never dreamed:  to develop along physically sexual lines opposite from what we now inhabit.  Embryology records how our present result is the mechanical outcome of hormones and physical processes.   It’s awesome to contemplate:  we all start out the same.  We don’t need to fabricate gender equality – we just need to return to it.

We’re the same when we start out, we’re not the same when we grow up…but we actually have a lot more in common than many people are prepared to admit, and we harbor remnants of our original potential in our very flesh.

The body is part of the soul – what does all this say about our eternal nature?  That is the question I wish to explore in this series.

Embryology makes a strong case for the inherent equality of all members of the human family.  The body is like clay, males and females shaped uniquely but still essentially the same.  This does not necessarily nullify masculinity or femininity, except perhaps the role each plays in eternal salvation.

Bodily differences make it possible for us to literally come together.

Bodily differences can also tear us apart.

Which would God have us choose?


Tomorrow:  Investigating The Reality of Sexual Variation