Where Is Sex?

[footfootfoot]

Originally Posted by rkzenrage

...I want sex all the time.

That's only because you're horny.

[9th Engineer]

Hmmm, I'll look into some stats but give me a little for numbers. The reason I mentioned men specifically is that males are more vulnerable due to the method of sex differentiation. I'll explain, but for now I'll exclude the disorders. There are four major steps in normal human sex differentiation:
1: Fertilization and determination of genetic sex
2: Formation of organs common between both sexes
3: Gonadal differentiation
4: Differentiation of the internal ducts and external genitalia

The first step is the obvious one, you either get an X or a Y chromasome from your father which determines your genetic sex, either XX female or XY male. In the second, the embryo diffentiates into the cell which will become most of your organs, lungs, heart, kidneys, you get the idea. However the first stage of gonad development is also common, all embryos develop the same gonadal ridges, internal ducts, and external genitalia. Now the gonadal ridges are plainly visible at 5 weeks, and is a critical stage, if you have defects in DAX-1, SOX-9 or a number of different genes, you will not develop either testes or ovaries. By the 7th week, both male and female fetuses have both the Mullerian and Wolffian ducts, while appearing female due to the presence of urethral folds and the urogenital opening.
Now, part of what Maggie was referring to occurs in the third stage, the differentiation of the gonadal ridge into either testes or ovaries. Remember how up until this point the fetus was anatomically female? At this point if the Y chromosome is present then the SRY factor will cause it to develop into testes. The female anatomy is caused by the lack of a differentiating factor, meaning that if something goes wrong at this stage the fetus automatically developes female genitalia while still being chromasomally male.
The last step is similar. If testes are present then the sertoli cells will begin to produce MIS (mullerian inhibiting substance) which will halt the growth of the mullerian ducts present since the 2nd phase. In addition, androgens are now being released by the leydig cells which will cause further development of the wolffian ducts (becoming the epididymis, vas deferens, etc). The female counterparts are once again determined by the absence of these differentiating factors.
Now you're probably familiar with hermaphroditism, and know that it comes in three varieties, true, male, and female. We didn't cover what causes true hermaphroditism, but the female variation is usually caused by congenital adrenal hyperplasia (adrenal glands which overproduce testosterone), and the male variation is typically androgen insensitivity syndrome which is exactly what it sounds like.
That's all we covered and I can get from my textbooks, I might look up some case studies on EBSCO or the medical database, but don't hold your breath right away. I just started Christmas break, and researching this stuff in more detail than I have to know is not high on my priority list at the moment.

Can anyone direct me to a good eggnog recipe?