development of external and internal genitalia ovaries embryology

1. DEVELOPMENT OF EXTERNAL
& INTERNAL GENITALIA
DR. PREKSHA JAIN
DR. MEDHA NAGPURE

2.  Embryonic structures involved are intermediate mesoderm & the
cloaca
 INTERMEDIATE MESODERM: Part between paraxial & lateral plate
mesoderm
 Forms bulging cranial to caudal = Nephrogenic cord
 4 structures develop lateral to medial
1. Paramesonephric duct
2. Mesonephric duct
3. Mesonephros
4. Gonad
DEVELOPMENT OF UROGENITAL
SYSTEM

4. CLOACA
VESICOURETHRAL
CANAL
PRIMITIVE
URETHRA
URINARY
BLADDER
DEFINITIVE
UGS
PELVIC PART PHALLIC PART
RECTUM

5. GONADS
 4th week
 Thickened mesothelium on medial side of mesonephros
 Gonadal ridges @ 7th wk
 Divide into CORTEX & MEDULLA
 Migration of primordial germ cell along dorsal mesentery reach
@ 6th wk

6. 46XY 46XX
INDIFFERENT GONAD
TESTIS OVARY
SRY GENE
MISPARAMESONEPHRIC
DUCT
TESTOSTERONE
MESONEPHRIC DUCT
DHT
EXTERNAL GENITALIA
ESTROGEN
PARAMESONE
PHRIC DUCT
EXTERNAL
GENITALIA

7. PARAMESONEPHRIC DUCT
• Mullerian ducts form 5-6th week.
• Formed by invagination of coelomic epithelium.
• Wolffian ducts serve as migration template.
• If wolffian duct fails mullerian duct donot develop.
• Fuse with other side caudally in midline to form UTERO-
VAGINAL CANAL & sheet of peritoneum which forms BROAD
LIGAMENT
• Caudal end joins phallic part of UGS
• In females it forms tubes, uterus & upper 1/3rd of vagina
• In males remnants forms prostratic utricle (~uterus) & appendix
of testis

9. 3 phases of Mullerian duct development
PHASES GENE
Selection of cells in coelomic
epithelium
Lim 1
Epithelial invagination Wnt family
Duct elongation
Duct differentiation
Pax2
Pax8

11. MALE EMBRYONIC
STRUCTURE
FEMALE
Testis INDIFFERENT GONAD Ovary
Seminiferous tubules CORTEX Follicles
Rete testis MEDULLA Rete ovary
Gubernaculum testis GUBERNACULUM Ovarian & Round lig
Efferent ductules MESONEPHRIC TUBULES Epo & paraoophoron
Duct & appendix of Epididymis
Ductus deferens
Ejaculatory duct & Seminal vesicle
Ureter, renal pelvis, Collecting duct
MESONEPHRIC DUCT Duct of epoophoron
Duct of Gartner
No homologous
Same
Appendix of testis PARAMESONEPHRIC DUCT Uterus, Tubes, upper
1/3rd of vagina & Hydatid
Bladder
Urethra
Prostate
Prostatic utricle
UROGENITAL SINUS Bladder
Urethra
Urethral & paraurethral
glands
Vagina

12. Penis
Glans penis
GENITAL TUBERCLE Clitoris
Glans clitoris
Ventral aspect of penis URETHRAL FOLDS Labia minora
Scrotum GENITAL SWELLINGS Labia majora

14. UTERUS & TUBES
 Begins @ 7-8wk completes by 12th wk
 EPITHELIUM: fused paramesonephric duct
 MYOMETRIUM: surrounding mesoderm increase in thickness
& unfused parts embedded to form fundus
 TUBES: develop from unfused paramesonephric ducts
 FIMBRIAE: invagination of coelomic epithelium

17. CERVIX & VAGINA
 @ 20th week condensation of stromal cells around fused
mullerian duct forms cervix
 Part where Uterovaginal canal (meso) & Phallic part of UGS
(endo) meet lead to formation of vaginal plate.
 Sinovaginal bulb form from endoderm
 Vaginal plate from mesoderm & endoderm
 Canalisation of vaginal plate
 Hymen(endo) is junction of vagina plate & UGS

19. EXTERNAL GENITALIA
 Elongation of UG membrane occurs
 Mesoderm on both sides heap up to form primitive URETHRAL
FOLDS later forms Labia Minora (endo & ecto)
 3 elevations (9 weeks):
1. GENITAL TUBERCLE forms clitoris
2. GENITAL SWELLINGS forms Labia Majora
 UG membrane breaks leads to formation of VESTIBULE

20. 9 weeks
10 weeks
12-14
weeks

22. OVARY
 Genital ridges develop on medial side of mesonephros by
thickening of coelomic epithelium
 Cords of cells(sex cords or medullary cords) grows into
underlying mesoderm
 Primordial germ cells migrate to form oocytes
 Sex cord breaks forms masses that surround one oocyte to
form PRIMORDIAL FOLLICLE
 INTERSTITIAL GLANDS differentiate from mesenchyme of
gonad

25. DEVELOPMENT OF OVARY
 Stages:
1. Indifferent gonad stage
2. Differentiation
3. Oogonal multiplication & oocyte formation
4. Follicle formation

26. BIPOTENTIAL GONAD
TESTIS OVARY
• TDF on SRY gene on Y
• AMH
• SOX9
• FGF9
CORTICAL REGRESSION
MEDULLARY PROLIFERATION
• Lack of SRY
• DAX1
• WNT4
• RSPO1
CORTICAL PROLIFERATION
MEDULLARY REGRESSION
LEYDIG CELLS SERTOLI CELL
TESTOSTERONE
WOLFFIAN
DUCT
DHT
MALE EXTERNAL GENITALIA
AMH
MULLERIAN
DUCT
FEMAL EXTERNAL
GENITALIA
2 wk later

27. 2.Differentiation
 Male phenotype depend on AMH & testosterone
 Female phenotype depend on absence of these products
 AMH Receptor gene mutation in 46XY –
Internal female genitalia
External male genitalia
 Small amount of AMH in ovary help in oocyte maturation &
follicular development
 Serum AMH levels correlate with follicles present & response to
ovulation induction

28. LHHCG & ACTH 20 WEEKS
STIMULATION OF LEYDIG CELLS
TESTOSTERONE

29. 3.OOGONAL MULTIPLICATION &
OOCYTE FORMATION
6-8wk 20 wk
(7 million)

30. 4.Follicle formation

31. • Ovary forms in lumbar region descends to true pelvis.
• Gubernaculum extend from ovary to labium majus .
• Attach at junction of tube & uterus.
• Persists as Round ligament
DESCENT OF OVARY

32.  Intermediate mesoderm: 3rd week
 Pronephros: 4th week & regress
 Mesonephros: 4th week function @ 6-10th week
 Metanephros: 4th week function from 12th week
 Mullerian ducts: 6th week
 Primordial germ cells develop in yolk sac : 4th
 Migrate : 6th
 Gonads remain as indifferent : 6th
 Interstitial cells produce testosterone : 8th
 Sec sex cords: 10-12th
 Primordial follicles: 16th
 Urethral folds: 3rd mth
 External genitalia: 7th and 9th week
 Urorectal septum: 4th and 7th week
 Vagina: 20th
TIME TABLE OF EVENTS