• Describe the development of gonads (indifferent stage) and sex determination. • Describe the development of testis and ovaries and the related structures. • Describe the development of the genital ducts. • Describe the development of male and female glands. • Describe the development of the male and female external genitalia. • Discuss the related developmental anomalies.  • Both the urinary &reproductive systems are closely related (structurally & developmentally) • Urogenital system develop from the intermediate mesoderm • Urogenital ridge is a longitudinal elevation of the mesoderm lateral to the dorsal aorta • Nephrogenic cord (ridge) develop in the urogenital ridge • Gives rise to part of the urinary system • Genital (gonadal) ridge develop close to the nephrogenic cord • Gives rise to part of the genital system

1. Dr. NDAYISABA CORNEILLE
CEO of CHG
MBChB,DCM,BCSIT,CCNA
Supported BY

2. Objectives
• Describe the development of gonads
(indifferent stage) and sex determination.
• Describe the development of testis and
ovaries and the related structures.
• Describe the development of the genital ducts.
• Describe the development of male and female
glands.
• Describe the development of the male and
female external genitalia. • Discuss the related
developmental anomalies.
Dr Ndayisaba Corneille 2

3. Development of Urogenital
System
• Both the urinary &reproductive systems are closely
related (structurally & developmentally)
• Urogenital system develop from the intermediate
mesoderm
• Urogenital ridge is a longitudinal elevation of the
mesoderm lateral to the dorsal aorta
• Nephrogenic cord (ridge) develop in the urogenital ridge
• Gives rise to part of the urinary system
• Genital (gonadal) ridge develop close to the nephrogenic
cord
• Gives rise to part of the genital system
Dr Ndayisaba Corneille 3

4. Contin…
Dr Ndayisaba Corneille 4

5. Development of Gonads
• Early development of male & female gonads are
similar (indifferent stage – indifferent gonads)
• Development of gonads begin in the 5thweek •
Source of gonadal development • Mesothelium of
posterior abdominalwall • lateral somatic mesoderm –
cortex • Proliferate and form gonadalridge • Primary
sexcords • In female formovary • Underlying
mesenchyme – intermediate mesoderm –medulla • In
male formtestis • Primordial germ cells – from the
yolksac • Migrate via mesentery & mesenchyme to the
primary sex cords (6thweek)
Dr Ndayisaba Corneille 5

6. Sex Determination
• Y chromosome has SRY gene in the sex determining
region for testis determining factor(TDF)
• Presence of TDF determines the differentiation of
testis
• Primary sex cords (in medulla) → seminiferous
tubules
• Absence of Y chromosome &TDF results in ovary
formation
• Testosterone from fetal testis determines male
characteristics
• Female characteristics determined without hormonal
effect
Dr Ndayisaba Corneille 6

7. Development of Testes
• Primary sex cords extend into medulla and form
seminiferous cords (obliterated tubules) - the
primitive sex cords continue to proliferate and
penetrate deep into the medulla to form the testis
or medullary cords
• The cords break up into a network of tiny cell
strands that later give rise to tubules of the rete
testis
• Rete testis connect with 15‐20 mesonephric
tubules (Wolfian ducts) → efferent ductules
• Mesonephric duct becomes ductus epididymis
Dr Ndayisaba Corneille 7

8. Development of Testes
• The fibrous tunica albuginea form - separates
the testis cords from the surface epithelium
• In the fourth month, the testis cords become
horseshoe-shaped, and their extremities are
continuous with those of the rete testis. Testis
cords are now composed of primitive germ cells
and sustentacular cells of Sertoli derived from
the surface epithelium of the gland.
• Testis enlarge & separate from the abdominal
wall leaving a mesentery (mesorchium)
Dr Ndayisaba Corneille 8

9. Contin…
Dr Ndayisaba Corneille 9

10. Development of Testes
• Interstitial (leydig) cells form from the mesenchyme
between seminiferous cords
• By 8th week secrete testosterone under influence of hCG
• Induce differentiation of mesonephric ducts &
externalgenitalia
• Sertoli cells derived from surface epithelium of testis
• Secrete antimullerian hormone (AMH) at 6‐7week
• Suppresses development of paramesonephric
(mullerian)ducts
• Spermatogonia develop from primordial germcells
Dr Ndayisaba Corneille 10

11. Development of Ovaries
• In female embryos with an XX sex chromosome complement and no Y
chromosome, primitive sex cords dissociate into irregular cell clusters.
• These clusters, containing groups of primitive germ cells, occupy the
medullary part of the ovary.
• Later, they disappear and are replaced by a vascular stroma that forms
the ovarian medulla.
• In the seventh week, it gives rise to a second generation of cords, cortical
cords, which penetrate the underlying mesenchyme but remain close to the
surface.
• In the third month, these cords split into isolated cell clusters. Cells in
these clusters continue to proliferate and begin to surround each
oogonium with a layer of epithelial cells called follicular cells.
• Together, the oogonia and follicular cells constitute a primordial follicle
• Extend to underlying mesenchyme at early fetal life
Dr Ndayisaba Corneille 11

12. Contin…
Dr Ndayisaba Corneille 12

13. Development of Ovaries
•In embryos with an XX sex chromosome
configuration, medullary cords of the gonad
regress, and a secondary generation of cortical
cords develops.
In embryos with an XY sex chromosome complex,
medullary cords develop into testis cords, and
secondary cortical cords fail to develop.
• Ovary separate from the abdominal wall leaving a
mesentery(mesovarium)
Dr Ndayisaba Corneille 13

14. INFLUENCE OF PRIMORDIAL GERM CELLS ON DIFFERENT GONARDS
Dr Ndayisaba Corneille 14

15. Development of Genital Ducts
• In the indifferent stage two ducts develop
(5th‐6thweek)
• Mesonephric (wolffian) ducts from mesonephrone
• Important in male genital structures
• Disappear in female
• Paramesonephric (mullarian) ducts – develop
lateral to the gonads & mesonephricducts
• Form from longitudinal invagination of the
mesothelium
• Important in female genital structures
• Disappear in male
Dr Ndayisaba Corneille 15

16. Development of Genital Ducts
Dr Ndayisaba Corneille 16

17. Development of Genital Ducts
Dr Ndayisaba Corneille 17

18. Development of Genital Ducts
Mesonephric ducts
• Proximally – form epididymis
• Distally – form ductus deferens & ejaculatory duct
• Lateral outgrowth give rise to seminal vesicle
Paramesonephric ducts
• Rostrally (with funnel shape opening into the abdomen)
• Caudally they cross anterior to mesonephric ducts &
fuse together forming uterovaginal primordium
• Ends at the posterior wall of the urogenital sinus
• Results in an elevation called sinus tubercle
Dr Ndayisaba Corneille 18

19. Influence of the sex glands on further sex
differentiation.
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20. Influence of the sex glands on further sex differentiation.
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21. Formation of the Peritoneal
Structures
• The fusion of the distal parts of the
paramesonephric ducts extend parts of the
peritoneum towards the midline
• The extended peritoneum forms the broad
ligament
• Anterior to it forms the vesicouterine pouch
• Posterior to it forms the rectouterine pouch
Dr Ndayisaba Corneille 21

22. Continuation..
Dr Ndayisaba Corneille 22

23. Development of Female Genital
Organs
• Uterine tubes develop from proximal part of
paramesonephric ducts • Uterus develops from
the uterovaginal primordium
• Vagina develops from the urogenital sinus
• Sinus tubercle induces the outgrowth of
sinovaginal bulbs → vaginal plate →vagina
• Separation between urogenital sinus & vagina
→hymen
Dr Ndayisaba Corneille 23

24. Development of Female Glands
• Urethral & paraurethral glands develop as
buds from urethra
• Greater vestibular glands develop from
outgrowth of urogenital sinus
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25. Formation of uterus and Vagina
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26. Formation of uterus and Vagina
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27. Development of Male Glands
• Seminal vesicle develop from a Lateral
outgrowth of the distal part of the mesonephric
duct
• Prostate gland develop from endodermal
outgrowth of the prostatic urethra into the
surrounding mesenchyme
• Bulbourethral glands develop from outgrowths
of the penile urethra
Dr Ndayisaba Corneille 27

28. Development of External Genitalia Indifferent Stage
(4th‐7thweeks)
• Genital tubercle formed from mesenchymal
proliferation at the cranial end of the cloacal
membrane
• Phallus is an elongated genital tubercle
• Urogenital (urethral) & labioscrotal folds
develop on sides of the cloacal membrane
Dr Ndayisaba Corneille 28

29. Development of External Genitalia Indifferent Stage
• Cloacal membrane separated into urogenital
membrane (anteriorly) and anal membrane
(posteriorly) by the urorectal septum
• The end of the urorectal septum form the
perineal body
• After a week the membranes rupture and form
anus & urogenital orifice
Dr Ndayisaba Corneille 29

30. Indifferent stages of the external
genitalia.
Dr Ndayisaba Corneille 30

31. Development of Male External
Genitalia
• This is under the influence of androgens secreted by
the Testis
• Phallus (genital tubercle) enlarges and elongates to
form penis
• Penile corpora formed by phallus mesenchyme
• Urogenital folds fuse & close the urethral groove
forming spongy urethra. (Site of fusion – penile raphe)
• Prepuce formed by circular ectodermal ingrowth
around the glans
• Scrotum formed by the fusion of the labioscrotal
folds. (Site of fusion is the scrotal raphe)
Dr Ndayisaba Corneille 31

32. Development of male external
genitalia
Dr Ndayisaba Corneille 32

33. Development of Female External
Genitalia
• The process is stimulated by Estrogen
• Phallus elongates slightly to become the
clitoris
• Urogenital folds form the labia minora
• Fuse posteriorly to form frenulum of the labia
minora
• Labioscrotal folds form the labia majora
• Fuse posteriorly & anteriorly to form posterior
& anterior labial commissures
Dr Ndayisaba Corneille 33

34. Development of Female External
Genitalia
Dr Ndayisaba Corneille 34

35. Development of Inguinal Canal
• While mesonephric duct degenerates, a ligament
(gubernaculum) appears
• Gubernaculum connects the gonads with the
labioscrotal swellings through the abdominal wall
• Peritoneal evagination (processus vaginalis) follow
the gubernaculum taking the layers of the abdominal
wall in front of it forming the inguinal canal
• Processus vaginalis guide the descent of testis
through inguinalcanal • Gubernaculum in females form
( Cranially – ovarian ligament, Caudally – round
ligament) Dr Ndayisaba Corneille 35

36. Female Genital Malformation
• Double uterus
• Failure of fusion of inferior part of
paramesonephric ducts
• Bicornuate uterus
• Failure of fusion in the superior part •
Unicornuate uterus • Failure of development of
one paramesonephric duct
Dr Ndayisaba Corneille 36

37. Uterine and Vaginal abnormalities
Dr Ndayisaba Corneille 37

38. Male Genital Malformation
• Hypospadias (1/300) - External urethral orifice
in the ventral side of Glans (glandular
hypospadias)
• Failure of canalization of glandular plate
• Body of penis (penile hypospadias)
• Failure of fusion of urogenital folds
(Epispadias) - Orifice opens dorsally at the root
of the penis
• Dorsal development of genital tubercle
Dr Ndayisaba Corneille 38

39. Male Genital Malformation
Dr Ndayisaba Corneille 39

40. Male Genital Malformation
Testicular anomalies
• Cryptorchidism (undescended testes) : 3‐4% of
full term men - Found in its path
• Ectopic testes - Deviate from its path
Dr Ndayisaba Corneille 40

41. END
Dr Ndayisaba Corneille
THANKS FOR LISTENING
By
DR NDAYISABA CORNEILLE
MBChB,DCM,BCSIT,CCNA
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amentalhealths@gmail.com/
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