7.7A. Endocrine physiology of sexual development.

Question 1

I. Physiology of sexual development
1. What is testis determining factor? How is it developed?

Answer 1

Question 2

I. Physiology of sexual development - Race of SOX9 expression in MALE
2A. Describe Race of SOX9 expression in MALE?

Answer 2

Question 3

I. Physiology of sexual development - Race of SOX9 expression in MALE
2B. What is the role of TDF?

Answer 3

• TDF induces transcription of 2 transcription factors: Sry and Sf1, which in turn induce transcription of SOX9, which helps the indifferent gonad to become testis

Question 4

I. Physiology of sexual development - Race of SOX9 expression in MALE
2C. What is the role of SOX9

Answer 4

• SOX9 helps the indifferent gonad to become testis
• SOX9 also inhibits β-catenin, a hormone that stimulates development of the female pathway

Question 5

I. Physiology of sexual development - Race of SOX9 expression in MALE
2D. What is the role of Leydig cells?

Answer 5

Leydig cells of the new testis secrete testosterone and the Sertoli cells secrete AMH, which degrade the components of the female genital tract that were also developing

Question 6

I. Physiology of sexual development - Race of SOX9 expression in MALE
2E. What is the role of testosterone?

Answer 6

• Testosterone stimulates growth + differentiation of the Wolffian duct into the epididymis, vas deferens, seminal vesicles and ejaculatory ducts

Question 7

I. Physiology of sexual development
3A. Describe Race of SOX9 expression in FEMALE

Answer 7

• Without Y chromosome, Wnt4 stimulates β-catenin, which inhibits SOX9 and helps
  transform the indifferent gonad into an ovary
• No AMH, so Müllerian ducts will proliferate and form the oviduct, uterus, etc.

Question 8

I. Physiology of sexual development
3B. What is the role of Wnt4?

Answer 8

• Without Y chromosome, Wnt4 stimulates β-catenin, which inhibits SOX9 and helps transform the indifferent gonad into an ovary

Question 9

I. Physiology of sexual development - Development of sex specific gonads
4. Describe Development of sex specific gonads

Answer 9

Question 10

I. Physiology of sexual development - Development of sex specific gonads
5. Describe the development of Primitive testis

Answer 10

Question 11

I. Physiology of sexual development - Development of sex specific gonads
6. Describe the development of Primitive ovary

Answer 11

Primitive ovary – develops from the cortex:
- Medulla of the gonad regresses
- Interior of gonad is filled with mesenchyme that is highly permeated by blood vessels
- Masses of cortical cells split up into secondary sex cords, which surround the oogonia

Question 12

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
7. When does Development of sexual ducts (internal genitalia) occur?

Answer 12

Occurs by the 9th week of gestation

Question 13

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
8A. Describe the development of Male internal genitalia?

Answer 13

Question 14

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
8B. In the development of Male internal genitalia
=> What are the hormones that affect this development?

Answer 14

Their development is influenced by testosterone secreted by the Leydig cells

Question 15

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
8C. What is the role of Sertoli cells in the development of Male internal genitalia?

Answer 15

Question 16

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
8D. Does Wolffian duct cells express α- reductase (DHT)?

Answer 16

NO!!!!

Question 17

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
9A. Describe the development of Female internal genitalia

Answer 17

Question 18

I. Physiology of sexual development - Development of sexual ducts (internal genitalia)
9B. In the development of Female internal genitalia,
The Müllerian duct will establish 3 functional organs
=> What are they?

Answer 18

1) Upper end -> fimbria
2) Middle of both duct fuse -> fundus + body of uterus
3) Distal end -> uterovaginal primordium

Question 19

I. Physiology of sexual development - Development of external genitalia
10. When does Development of external genitalia occur?

Answer 19

Occurs by the 14th week of gestation (between 14-19th week, the gender can be determined)

Question 20

I. Physiology of sexual development - Development of external genitalia
11. What does the requirement for Development of external genitalia?

Answer 20

DHT is needed for further differentiation of the male genitalia
- Genital swelling + fold surrounds the cloacal membrane
- Genital tubercle will grow in both genders

Question 21

I. Physiology of sexual development - Development of external genitalia
11. What does the requirement for Development of external genitalia?

Answer 21

DHT is needed for further differentiation of the male genitalia
- Genital swelling + fold surrounds the cloacal membrane
- Genital tubercle will grow in both genders

Question 22

I. Physiology of sexual development - Development of external genitalia
12. Describe Development of MALE external genitalia

Answer 22

• Genital tubercle => glans penis
• Urogenital folds => penile shaft
• Labio-scrotal swellings => scrotum

Question 23

I. Physiology of sexual development - Development of external genitalia
13. Describe Development of FEMALE external genitalia

Answer 23

• Genital tubercle => clitoris
• Urogenital folds => labia minora
• Labio-scrotal swellings => labia
  majora
• Ventral fusion of the labio-scrotal swellings => mons pubis

Question 24

I. Physiology of sexual development - Puberty
14. What are the main features of puberty

Answer 24

Question 25

I. Physiology of sexual development - Puberty
15. What are the features of Adrenarche?

Answer 25

Question 26

I. Physiology of sexual development - Puberty
16. What are the features of Gonadarche?

Answer 26

Question 27

I. Physiology of sexual development - Puberty
17A. What are the hormones that influence the production of GnRH during puberty?

Answer 27

Question 28

I. Physiology of sexual development - Puberty
17B. How does leptin influence the production of GnRH during puberty?

Answer 28

Adipocytes: leptin => GnRH secretion↑

Question 29

I. Physiology of sexual development - Puberty
17C. How does insulin influence the production of GnRH during puberty?

Answer 29

Pancreas: insulin
=> GnRH secretion↑

(+ lipid storage in adipocytes↑
=> ↑leptin
=> ↑GnRH secretion)

Question 30

I. Physiology of sexual development - Puberty
17D. How does IGF-1 influence the production of GnRH during puberty?

Answer 30

Liver: IGF-1 => GnRH secretion↑

Question 31

I. Physiology of sexual development - Puberty
17E. How does ghrelin influence the production of GnRH during puberty?

Answer 31

Empty stomach: ghrelin
=> ↓GnRH secretion

Question 32

I. Physiology of sexual development - Events of male puberty:
18A. What are the events of male puberty?

Answer 32

Question 33

I. Physiology of sexual development - Events of male puberty:
18B. What can we see in males around age of 9?

Answer 33

• Around age of 9, we can see increase in testosterone production, because of ↑GnRH, LH, FSH production