A baby’s sex is determined at the time of conception.
When the baby is conceived, a chromosome from the sperm cell,
either X or Y, fuses with the X chromosome in the egg cell,
determining whether the baby will be female or male.
Two X’s means the baby will be a girl, and XY means it will be a boy.
But even though gender is
determined at conception,
the fetus doesn’t develop its
external sexual organs
until the fourth month of pregnancy.
Let’s go to seven weeks after conception. You can see from the front
that the fetus appears to be sexually indifferent,
looking neither like a male or a female.
Over the next five weeks,
the fetus begins producing hormones
that cause its sex organs to grow
into either male or female organs.
This process is called sexual differentiation.
We don’t know what sex this fetus is yet,
so we’ll have to be hypothetical here....
Now, if the fetus is a male,
it will produce hormones called androgens,
which will cause his sexual organs
to form like this...
On the other hand,
a female fetus would not produce androgens;
she would produce estrogens…
so her sex organs would form like this...
Now let’s take a look at something
you may have missed.
At seven weeks,
the sex organs of a male and female
look identical.
Let’s add some color to see what happens
during sexual differentiation.
Keep your eye on the genital tubercle.
See that?
The genital tubercle formed
the penis in the male,
and the clitoris in the female.
The penis and clitoris are called sexual analogs
because they originate from the same structure.