DEVELOPMENT OF EXTERNAL & INTERNAL

GENITALIA

DR. PREKSHA JAINDR. MEDHA NAGPURE

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 medial1. Paramesonephric duct2. Mesonephric duct 3. Mesonephros 4. Gonad

DEVELOPMENT OF UROGENITAL SYSTEM

CLOACA

VESICOURETHRAL CANAL

PRIMITIVE URETHRA

URINARY BLADDER

DEFINITIVE UGS

PELVIC PART PHALLIC PART

RECTUM

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

46XY

46XX

INDIFFERENT GONAD

TESTIS

OVARY

SRY GENE

MISPARAMESONEPHRIC DUCT

TESTOSTERONEMESONEPHRIC

DUCT

DHTEXTERNAL GENITALIA

ESTROGEN

PARAMESONEPHRIC DUCT

EXTERNAL GENITALIA

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

3 phases of Mullerian duct development

PHASES GENE

Selection of cells in coelomic epithelium

Lim 1

Epithelial invagination Wnt family

Duct elongationDuct differentiation

Pax2Pax8

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 EpididymisDuctus deferensEjaculatory duct & Seminal vesicleUreter, renal pelvis, Collecting duct

MESONEPHRIC DUCT Duct of epoophoronDuct of Gartner No homologousSame

Appendix of testis PARAMESONEPHRIC DUCT

Uterus, Tubes, upper 1/3rd of vagina & Hydatid

BladderUrethraProstateProstatic utricle

UROGENITAL SINUS BladderUrethraUrethral & paraurethral glandsVagina

PenisGlans penis

GENITAL TUBERCLE Clitoris Glans clitoris

Ventral aspect of penis URETHRAL FOLDS Labia minora

Scrotum GENITAL SWELLINGS Labia majora

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

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

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

9 weeks

10 weeks

12-14 weeks

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

DEVELOPMENT OF OVARY

Stages:1. Indifferent gonad stage2. Differentiation3. Oogonal multiplication & oocyte formation4. Follicle formation

BIPOTENTIAL GONAD

TESTIS OVARY

• TDF on SRY gene on Y

• AMH• SOX9• FGF9

CORTICAL REGRESSIONMEDULLARY PROLIFERATION

• Lack of SRY• DAX1• WNT4• RSPO1

CORTICAL PROLIFERATIONMEDULLARY REGRESSION

LEYDIG CELLS

SERTOLI CELL

TESTOSTERONE

WOLFFIAN DUCT

DHT

MALE EXTERNAL GENITALIA

AMH

MULLERIAN DUCT

FEMAL EXTERNAL GENITALIA

2 wk later

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

LHHCG & ACTH 20 WEEKS

STIMULATION OF LEYDIG CELLS

TESTOSTERONE

3.OOGONAL MULTIPLICATION & OOCYTE FORMATION

6-8wk

20 wk(7 million)

4.Follicle formation

• 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

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