Fetal Development of Sexual Anatomy

Question 1

Every mammalian fetus has the…

Answer 1

…anatomical precursors for BOTH sexes

Question 2

Gonads

Answer 2

earliest sex structure to develop, same initial structure will become Testes or Ovaries

Question 3

something has to trigger which direction it will take

Answer 3

(X or Y chromosomes)

Question 4

Testis-Determining Factor (TDF)

Answer 4

Enzyme

genes turned on and the cells produce testosterone

gonads develop into testes

wolfian ducts transform into Vas Defrens

takes something extra to make the male

appears 6th - 8th week

Question 5

Gentalia

Answer 5

same initial strucutre in all fetuses,

develop into male or female anatomy, depending on Androgens/Not

Question 6

Wolfian and Muellerian ducts

Answer 6

in each fetus

their development depends on Androgens/Not

these become either Vas Defrens and Prostate

or

Fallopian Tubes and Uterus respectively

other system degenerates

Question 7

Testosterone

Answer 7

first androgen triggered by TDF

Question 8

genes controlling male/female body and brain development are

Answer 8

also present in BOTH sexes

Question 9

Androgen-Insenstive

Answer 9

cells that respond to testosterone unresponsive

default female form taken despite presence of Y chromosome

Question 10

to be fertile

Answer 10

takes 2 “Xs”

Question 11

The “switch”

Answer 11

is one the male’s Y Chromosome

it signals production of the Testis-Determining Factor Enzyme

occurs during CRITICAL PERIOD of fetal development

Question 12

genitals developed by

Answer 12

4th month

Question 13

if testosterone is what’s required to masculinize a fetus, how does more estrogen somehow masculinizes fetuses?

Answer 13

the similarity between the chemical structure of estrogen and testosterone

testosterone gets into the cell and then it turns into the estrogen and the estrogen then has the masculinizing effect

Question 14

if TDF is present =>

Answer 14

Male

Question 15

Testes

tdf

Answer 15

differentiate, producing Androgens, including Testosterone => Wolffian ducts and male genitalia develop

also produce Anti-Muellerian Hormone

Question 16

Alpha-Fetoprotein

Answer 16

produces by the fetus

it binds with estrogen so that it doesn’t play a role in determining the gender

fetus wants to determine its own gender: doesn’t want to be influenced by mother’s hormones

Question 17

Anti-Muellerian Hormone

tdf

Answer 17

inhibits development of Muellerian system

Question 18

if XY fetus is Androgen-Insensitive

Answer 18

its testes still produce Androgens and Anti-Muellerian Hormone, but since its Wolffian system’s androgen receptors are absent IT DOES NOT DEVELOP AND its Muellerian system is inhibited

so individual has no internal sex organs (infertile) except rudimentary, internal tests

external body develops as female, although without androgen stimulated pubic or secondary hair

Question 19

If XX fetus is exposed to Testosterone during critical period…

Answer 19

…develops as male or semi-male form, sometimes infertile

some tendency for these individuals to be homosexual, tho per body, brain, and/or societal influences??

Question 20

Testosterone enters fetal cells, where it is…

Answer 20

… converted (“aromatized”) into Estradiol (an Estrogen!) => male development

Question 21

why doesn’t mom’s estradiol masculinize every fetus?

Answer 21

Alpha-Fetoprotein

Question 22

Alpha-Fetoprotein

Answer 22

in fetal/infant blood, binds with Estrogen, preventing it from entering fetal cells (later inactivated)

Question 23

Excessive Estrogens

Answer 23

e.g. DES, synthetic estrogen to prevent miscarriage

can overwhelm safeguard, masculinize fetus