Week 7

Question 1

What does the fetus have at 6 weeks?

Answer 1

Bipotential primordium and rudimentary reproductive tracts

Question 1

What can bipotential primordium become?

Answer 1

testis or ovary

Question 2

Two types of ducts

Answer 2

Mullerian duct and Wolfian duct

Question 2

What gene does Y chromosome have?

Answer 2

SRY gene

Question 2

what does the Wolfian duct become?

Answer 2

Epididymis, vas deferens, and seminal vesicle

Question 2

what does the Mullerian duct become?

Answer 2

the fallopian tube, uterus, and upper vagina

Question 3

What happens at 10 weeks, if female?

Answer 3

1. Gonadal cortex becomes ovary
2. Gonadal medulla regresses.
3. Wolfian duct regresses (testosterone absent)
4. Mullerian duct becomes fallopian tube, uterus, upper 1/2 of vagina, cervix - AMH is absent

Question 3

What does SRY gene do?

Answer 3

Promotes testes development, encodes a transcription factor (TDF- testes determining factor)

Question 4

SF1 (Steroidogenic Factor 1)

Answer 4

This is a transcription factor involved in early gonadal development. It’s necessary for the formation of the bipotential gonad, which has the potential to develop into either testes or ovaries.

Question 5

SOX9

Answer 5

Once SRY is activated, it induces SOX9, another transcription factor essential for male gonadal differentiation. SOX9 is responsible for driving the production of other factors that are necessary for testes development.

Question 6

Signaling pathway of SRY

Answer 6

Starting from SF1 activating SRY in the presence of the Y chromosome.
SRY then activates SOX9.
SOX9 leads to the production of factors that develop Sertoli (produces AMH) and Leydig cells and prevent the formation of female reproductive organs.

Question 7

What promotes production of AMH

Answer 7

SOX9

Question 8

E10.5

Answer 8

At this stage, the embryo has a genital ridge, also known as an “indifferent gonad,” which has the potential to develop into either testes or ovaries.

Question 9

E11.5

Answer 9

In XY embryos (with an SRY gene), high levels of SOX9 are present, whereas in XX embryos (lacking SRY), SOX9 is absent.

Question 9

E12.5

Answer 9

The differentiation is established — in XY embryos, the gonad develops into testes, while in XX embryos, it develops into ovaries.

Question 10

SOX9 in XY Gonadal Development:

Answer 10

SRY and SF1: These factors together activate SOX9 in XY embryos.
SOX9 Activation Loop: Once SOX9 is activated, it promotes itself in a feedback loop along with factors such as PGD2, FGF9 + FGFR2, and SOX8.
β-catenin Suppression: SOX9 suppresses β-catenin, a signaling protein involved in ovarian development, ensuring the gonad develops into testes.

Question 11

What does SOX-9 initiate

Answer 11

Sertoli cell differentiation; cellular events downstream of SOX-9 rapidly organize testis structure

Question 12

Atypical hormone levels or action-XX

Answer 12

excessive exposure to androgens during early
gestation

Question 12

SOX9 in XX Gonadal Development:

Answer 12

WNT4 and RSPO1: These factors activate β-catenin in XX embryos, which suppresses SOX9, steering development towards ovaries.
FOXL2: Along with other unidentified factors, FOXL2 helps maintain low SOX9 levels, further ensuring ovarian development.

Question 13

XY: development of structures

Answer 13

1. Gonadal cortex regresses
2. The gonadal medulla forms a testis.
3. Wolfian duct forms epididymis, vas deferens, and seminal vesicle (testosterone present)
4. Mullerian duct regresses (AMH present)

Question 13

Atypical hormone levels or action - XY

Answer 13

atypical androgen synthesis (5 alpha reductase) or action

Question 14

DHT - structure location

Answer 14

external structures

Question 14

testosterone - structure location

Answer 14

internal structures