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development of external and internal genitalia ovaries embryology
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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
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