embryology

1. EMBRYOLOGY OF FEMALE
UROGENITAL SYSTEM
Dr Anuradha sawant

2. TOPICS
DEVELOPMENT OF FEMALE GENITAL SYSTEM
i. Gonads(Ovary)
ii. Reproductive Ducts
iii. External Genitalia
DEVELOPMENT OF FEMALE URINARY SYSTEM

3. DEVELOPMENT OF THE UROGENITAL
SYSTEM
Intraembryonic Mesoderm is subdivided
into three parts
i. Paraxial mesoderm - Forms Somites-
axial skeleton/musculature/dermis
ii. Lateral plate mesoderm-
muscle/connective tissue layers / trunk
walls
iii. Intermediate mesoderm – Lying
between the two –forms the
urogenital ridge
Transverse section of embryo at 3 weeks

4. UROGENITAL RIDGE
• Intermediate mesoderm forms a bulging on the posterior
abdominal wall lateral to the dorsal mesentery of the gut
called the Urogenital Ridge
• Urogenital Ridge is divided into two parts
i. Genital Ridge (Medial) – Forms genital system
ii. Nephrogenic Cord (Lateral) – Forms urinary system

5. DEVELOPMENT OF GONADS (OVARY)

6. INDIFFERENT PHASE (3rd – 6th WEEK)
Genital ridges – Formed by the proliferating germinal epithelium & condensation of
mesenchyme → Germinal epithelium further forms primitive sex cords
The primordial germ cells originate from epiblast and through the primitive streak
3rd week- They migrate to endoderm cells in yolk sac
4th week- Migrate through Dorsal mesentery to reach genital ridge
5th week- Arrive at primitive gonadal ridge
6th week- Invade the ridge

7. VIDEO ON THE DEVELOPMENT DURING
INDIFFERENT PHASE AND FORMATION OF
GENITAL RIDGE

8. HOW IS A PERSON’S GENDER IDENTIFIED?

9. FETAL SEX DETERMINATION
(i) Chromosomal gender: Established at the time of fertilisation (XX/XY)
(ii) Gonadal gender : Determined by development of testis / ovary
(iii) Phenotypic gender: Determined by the external genitalia and
secondary sexual characteristics

10. FETAL SEX DETERMINATION
SRY
(transcription
factor)
+
SOX9
(transcription
regulator)
FGF9 (chemotactic factor ) from testis-causes mesonephric
duct penetration at urogenital ridge
upregulates production of SF1 (steroidogenesis factor)-
stimulates differentiation of sertoli and leydig cells
Y chromosome has Testis determining gene-SRY
SRY is present on – Yp11
SRY initiates a cascade of autosomal genes
which results in sexual differentiation

11. FETAL SEX DETERMINATION
SF1+SOX9
↑AMH by acting on sertoli
cells –active regression of
paramesonephric duct
Upregulates gene-
↑synthesis of testosterone
&dihydrotestosterone

12. FETAL SEX DETERMINATION
WNT4(ovary
determining
factor)
Upregulates DAX1(nuclear
hormone receptor)-
inhibits SOX9
Regulates expression of
other genes-TAFII 105-acts
on ovarian follicle

13. FETAL SEX DETERMINATION

14. • Primitive sex cords degenerate →replaced by vascular stroma→
ovarian medulla
• Surface epithelium →forms cortical sex cords (week 7)→
isolated clusters (3rd month) →surround oogonium → primordial
follicle
DEVELOPMENT OF OVARY

15. VIDEO ON DEVELOPMENT OF OVARY

16. DESCENT OF OVARIES AND FATE OF
GUBERNACULUM
• Ovarian descent →Lumbar
region to true pelvis.
• Gubernaculum:
• Extends from ovary → Labium
Majus
• Attached to uterus at uterine
tube junction
• Forms following structures:
I. Suspensory ligament of ovary
II. Ligament of ovary
III. Round ligament of the uterus

17. VIDEO ON RELOCATION OF OVARIES

18. DEVELOPMENT OF REPRODUCTIVE DUCT
SYSTEMS IN FEMALE

19. • Both male and female embryo have 2 pairs
of genital ducts
(i) Mesonephric duct (Wolffian duct)
(ii) Paramesonephric duct (Mullerian duct)-
uterine tubes/ uterus/ part of the vagina
DEVELOPMENT OF FEMALE REPRODUCTIVE DUCTS

20. INDIFFERENT STAGE(3rd-6th WEEK)
• Paramesonephric ducts arise as longitudinal
invaginations of epithelium on urogenital ridge
• Cranially- Duct opens into the abdominal
cavity as a funnel
• Caudally – First runs lateral to mesonephric
duct – then crosses to midline- fuse with
opposite duct
• Caudal tip projects into urogenital sinus –
forms sinus tubercle

21. DEVELOPMENT OF UTERUS AND UTERINE TUBES
CERVIX AND UPPER VAGINA
I. Fimbriae – At cranial end as abdominal
opening of the tube
II. Uterine tubes – Unfused parts of
paramesonephric ducts
III. Fundus – Unfused horizontal part of
paramesonephric ducts
IV. Uterine cavity/Cervix/Upper vagina-
Uterovaginal canal
V. Endometrium - Fused
paramesonephric ducts (utero-vaginal
canal)
VI. Myometrium & Perimetrium -
Surrounding mesoderm

22. DEVELOPMENT OF VAGINA
• Two sinovaginal bulbs develop → forms vaginal plate → develops
lumen → vagina(5th month)→expands around uterus → forms vaginal
fornices
Hymen → sinus tubercle
• Vagina has dual origin:
Upper part –uterine canal
Lower part- urogenital sinus

23. VIDEO ON DEVELOPMENT OF FEMALE
REPRODUCTIVE DUCTS

24. WHAT IS THE CLASSIFICATION OF THE
MULLERIAN SYSTEM ANOMALIES?

26. FATE OF MESONEPHRIC DUCT IN FEMALES
Mesonephric ducts give rise to :
I. Ureteric bud (ureter, pelvis, calyces and collecting
tubules
II. Trigone of the bladder
III. The posterior wall of the female urethra
IV. Some vestigial structures seen in the broad ligament near
the ovary (next slide)

27. I. Epoophoron (above egg
basket) : Corresponds to
the epididymis and vasa
efferentia of the male
II. Paroophoron (near egg
basket): Corresponds to
paradidymis in male
III. Gartner’s duct : Equivalent
to male ductus deference
(sometimes presents as
gartner’s cyst)
VESTIGIAL STRUCTURES

28. DEVELOPMENT OF FEMALE EXTERNAL GENITALIA

29. INDIFFERENT STAGE
• @3rd week
Cranially-cloacal folds
unite-form Genital tubercle
Caudally - cloacal folds
divided into Urethral fold & Anal
fold
Till 6th week - sex indistinguishable

30. DEVELOPMENT OF FEMALE EXTERNAL GENITALIA
Estrogen stimulates the development
of external genitalia in females
• The genital tubercle → Clitoris
• The right and left genital swellings→
Labia Majora
• The primitive urethral folds → Labia
Minora
• Their posterior ends fuse →form
Posterior Commissure
• The urogenital membrane breaks
down → Vestibule

31. VIDEO ON DEVELOPMENT OF FEMALE
EXTERNAL GENITALIA

32. HOW WOULD YOU PROCEED IF YOU ARE UNABLE
TO IDENTIFY THE SEX OF THE BABY AT THE
DELIVERY TABLE?

33. CHRONOLOGY OF DEVELOPMENT

34. MALE AND FEMALE HOMOLOGUES DERIVED
FROM UNDIFFERENTIATED GENITAL SYSTEM

37. DEVELOPMENT OF THE URINARY SYSTEM