1. Reproductive System Embryology
生物及解剖學科
陳 瀅 18749

2. Study Goals Development of gonads Development of genital ducts
Development of external genitalia
Development of inguinal canal

3. Development of gonads 7th week indifferent state of sexual development
The gonads are derived from three sources
The mesothelium lining the posterior abdominal
wall
The underlying mesenchyme
The primordial germ cells

4. Development of gonads
5th week
6th week
7th week

5. Development of gonads gonadal ridge primordial germ cell
are visible in 4th week among the endodermal cells of the yolk sac
migrate along the dorsal mesentary of the hindgut to the gonadal ridges

6. Development of gonads Sex determination (after 7th week)
male – Y chromosome, which has a testis-determining factor (TDF)
female – XX chromosome

7. Development of gonads with the TDF gonadal cord  seminiferous cords
without the TDF
formation of ovaries
the type of gonads  determine the type of sexual differentiation (genital ducts and external genitalia)

8. Development of gonads Testes
gonadal cords condense and extend into the medulla  seminiferous cords
rete testis
tunica albuginea – a thick fibrous capsule
suspended by its own mesentery – mesorchium

9. Development of gonads Testes interstitial cells (Leydig)
8th week, the cells begin to secrete androgenic hormones – testosterone and androstenedione
human chorionic gonadotrophin (hCG) peak amount 8-12 week
Mullerian inhibiting substance (MIS)

10. Development of gonads Testes Sertoli cell
derived from the surface epithelium of the testis
MIS
spermatogonia
primordial sperm cells derived from the primordial germ cell

11. Development of gonads
E43 days
new born
21 weeks

12. Development of gonads Ovaries
gonadal cords extend into the medulla  rete ovarii
cortical cords from surface epithelium
16 week  primordial follicles, each of which consists of an oogonium (surrounded by follicular cells from surface epithelium)

13. Development of gonads Ovaries No oogonia form postnatally (2 million)
the surface epithelium called “germinal epithelium”
germ cells derived from the primordial germ cells
the ovary is suspended by a mesentary – the mesovarium

14. Development of gonads
E43 days
new born
14 days

15. Development of genital ducts
5th – 6th weeks, both pairs of genital ducts are present in the indifferent state
Mesonephric ducts play an essential role in male reproductive system
Paramesonephric ducts play an essential role in female reproductive system

16. Development of genital ducts

17. Development of genital ducts
male genital ducts and glands
testosterone
Mullerian inhibiting substance (MIS)

18. Development of genital ducts
male genital ducts and glands
prostate gland
endodermal cells
mesenchyme – stroma and smooth muscles

19. Development of genital ducts

20. Development of genital ducts
female genital ducts and glands
Without testosterone
and MIS
 mesonephric
ducts regress
 paramesonephric
ducts develop
The endometrial stroma and myometrium are derived from splanchnic mesenchyme
and upper part of vagina

21. Development of genital ducts

22. Development of genital ducts
female genital ducts and glands

23. Development of genital ducts
vagina
the endoderm of the urogenital sinus  epithelium
surrounding mesenchyme  fibromuscular wall

24. Development of genital ducts
vagina
Sinus tubercle  sinovaginal bulbs  vaginal plate
The central cells in the plate break down forming the lumen of vagina

25. Development of genital ducts
vagina
uterovaginal primordium + urogenital sinus

26. Anomaly of genital ducts

27. Development of external genitalia
4th – 7th weeks

28. Development of external genitalia
9 weeks
11 weeks
12 weeks

29. Development of external genitalia
male female male
7 weeks
10 weeks
10 weeks

30. Development of external genitalia
female
Congenital adrenal hyperplasia (CAH)

31. Androgen insensitivity syndrome
also called the testicular feminization syndrome
normal-appearing female, despite the presence of testis and a 46, XY chromosome

32. Anomaly of external genitalia
Hypospadias

33. Anomaly of external genitalia
congenital absence

34. Anomaly of external genitalia
Vaginal atresia

35. Development of inguinal canals
mesonephros  gubernaculum  labioscrotal swellings
peritoneum  inguinal canal
7 weeks
28 weeks

36. Ectopic testes

37. Congenital inguinal hernia

38. References Moore Persaud : The Developing Human 9th edition, 2012
Langman’s : Medical Embryology 11th edition, 2010