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Genital system d evelopment


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Development Of Human Reproductive System

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Genital system d evelopment

  1. 1. Genital System Development
  2. 2. FORMATION OF GONADAL RIDGES/GENITAL RIDGESProduced on the post.abdominal wallby the proliferation of epithelium andthe condensation of underlyingmesenchyme
  3. 3. FORMATON OF PRIMITIVE SEX CORDSMigration of PGCs from the endoderm in the wall ofyolk sac along the dorsal mesentery to thedeveloping gonad.During & Before migration Epithelium of genitalridges undergoes proliferation and penetrate theunderlying mesenchyme to form primitive sexcords which are connected to surface epithelium.Gonads at this stage are said to be “INDIFFERENT”gonad.
  4. 4. GENITAL DUCTS AT INDIFFERENT STAGE2 TypesParamesonephric(Mullerian)&Mesonphric(Wolffian)ducts.PARAMESONEPHRIC:Lie lateral to the mesonephricSuperiorly continuous with abd.cavityInferiorly they cross the mesonephric ducts caudomedially &join with those ofopposite side.Initially the two are separated from each other by a septum but later they fuse toform”UTERINE CANAL”that projects into the post.wall of urogenital sinus toraise a tubercle called”Paramesonephric/Mullerian tubercle”MESONEPHRIC:They open on either side of the tubercle into the urogenital sinus
  5. 5. DEVELOPMENT OF TESTIS1)Formation of Testis/Medullary cords:Under the influence of SRY gene which encodes TDF2)Formation of tubules of rete testis:Testis cords break up at the hilum of gland to form these tiny cell strands3)Formation of tunica albuginea:Dense fibrous C.T layer that separates testis cords from surface epi.4)Testis cords become horseshoe shaped&ther extremties become continuous with tubules of retetestis5)Comp.of testis cord:PGCs& Sustentacular cells5)Interstitial cells:Derived from mesenchyme of gonadal rdge b/w the testis cords.beginsecretingtestosterone in 8th week.6)Canalization of cords to form seminiferous tubules:occurs at puberty.s.tubules join tubules ofrete testis which enter the efferent ductules(rmnants of mesonephric sys tubules)7)Effernt ductules link mesonepphric ducts which develop into ductus deferens
  6. 6. DESCENT OF TESTESUrogenital mesentery suspends testes &mesonephros to post.abd wallMesonephros regressesCAUDAL GENITAL LIGAMENT:Caudal part of mesenteryGUBERNACULUM:Condensation of mesenchyme containing extracellular matrix extendingfrom the caudal pole of testis.Terminates in the inguinal region b/w differentiatingint&ext.oblique muscles before the descent of testes.EXTRABDOMINAL PORTION of gubernaculum extends frm inguinal to scrotal swellings.Passage is produced in the inguinal canal due to increase in intra abdominal pressure causedby growth of testisTestis reach the INGUINAL REGION:12weeksINGUINAL CANAL:28weeksSCROTUM:33weeksHormones responsible:Androgen&MISCOVERINGS:1)Reflected part of processus vaginalis forming visceral&parietal layer oftunica vaginalis.2)Derived from ant.abd wall through which it passes viz;Int.spermaticfascia(Transv.fascia)Cremastrc fascia(Int oblique)Ext.sperm fascia(Ext.oblique)Transversusabd doesn’t contribute any layerPROCESSUS VAGINALIS:Peritoneal evaginations on each side of midline in ventralabdominal wall that follows the course of gubernaculum.It forms INGUINAL CANALaccompanied by fascial&muscular layers of body wall.At birth or shortly thereafter,itsnarrow canal connecting it to peritoneal cavity gets obliterated.
  7. 7. DEVELOPMENT OF OVARY Dissociation of prim. sex cords in medulla into irregular cell clusters Clusters contain PGCsThat later disappear &are replaced by vascular stroma that formsovarian medullaFORM.OF CORTICAL CORDS:Unlike in males, surface epithelium undergoes proliferation to formcortical cords which penetrate the underlying mesenchymeBREAKING OF CORDS INTO ISOLATED CELL CLUSTERS:That surround 1 or more PGCsFATE OF PGCs: OogoniaFATE OF Epithelium.derived cells: Follicular cells
  8. 8. DESCENT OF OVARIESConsiderably lessFINAL POSITION:Just below the rim of true pelvisCranial genital ligament:Suspensory lig.of ovaryCaudal genital ligament:Lig.of ovary proper&Roundligament of uterus(extending to labia majora)
  9. 9. GENITAL DUCTSMALE FEMALEEPIGENITAL TUBULES:Remnants CRANIAL VERTICAL PART :of excretory tubules of develops into uterine tubemesonephric system that join the MIDDLE HORIZONTAL PARTrete testis to form efferent CAUDAL VERTICAL PART : Fusesductules with its partner from the opposite side to form uterine canalPARAGENITAL BROAD LIGAMENT : transverseTUBULES:Exc.tubules along the pelvic fold that extends from thecaudal pole of testis that don’t join lateral sides of fusedrete testis paramesonephric ducts towards the wall of pelvis Up border : Contains uterine tubes with ovaries on posterior surface
  10. 10. VAGINAFORMATION OF SINOVAGINAL BULBS:Shortly after the form.ofparamesonephric tubercle,evaginations appear from the pelvic part ofurogenital sinusFORMATION OF VAGINAL PLATE: Formed by the fusion of sinovaginal bulbsPROLIFERATION: Occurs in cranial region increasing the distance b/wuterus&urogenital sinusCANALIZATIONDUAL ORIGIN:1)Wing like expansions vaginal fornices.Paramesonephric inorigin.Originate from uterine canal2)Remaining part:From urogenital sinusHYMEN:Forms during perinatal like as a small opening through which vaginaremains separated from urogenital sinus.Made up of epithelial cells and thinlayer of vaginal cells
  11. 11. EXTERNAL GENITALIAINDIFFERENT STAGE:Mesenchymal cells from the prim.streak migrate around the cloacalmemb and raise slight elevations called”CLOACAL FOLDS”Cloacal folds:ANT:Urethral folds,POST:Anal foldsGENITAL TUBERCLE:Formed by fusion of urethral folds craniallyGENITAL SWELLINGS:Appear lateral to urethral swellings.Forms scrotalswellings in males&Labia majora in females
  12. 12. DEVELOPMENT OF EXT.GENITALIAMALE FEMALEGenital tubercle elongates to form Genital tubercle elongates to”PHALLUS” form”Clitoris”Elongation of phallus is Urethral folds don’t fuse ratheraccompanied by forward movement form labia minoraof urethral foldsEpi.of urethral groove forms Genital swellings form labia majoraurethral plateUrethral folds fuse thus closing off Urethral groove forms vestibuleurethral plate thus forming PENILEURETHRAUr.groove doesn’t extend into distal During early stages ofpart of phallus in the tip of glans development,genital tubercle is longer than in males.This often leads to mistake in sex determination during 3rd&4th months of gestationDistal most part of urethra is formedby the ectodermal cell proliferationfrom the tip of glans into the phallus
  13. 13. ANOMALIES KLINEFELTER’S SYNDROME:XXY(Non-disjunct.) UGs Under androgenization, Gynecomastia, Sexual retardation GONADAL DYSGENESIS:Oocytes absent,ovaries streak appearance Swyer’s syndrome:Normal females,Don’t menstruate,Don’t develop sec.sexual characterstics at puberty Turner’s syndrome:XOShort stature,Webbed neck,PCCR(Palate arched,Chest shield like,Cardiac&Renalabnormalities) HERMAPHRODITISM:Raised as females,Phenotype 46,XX.Genitalia ambiguus,femalelike,possess both ovarian&testicular tissue.PSEDOHERMAPHRODITISM: Genotype is masked by phenotype that closely resemblesthat of opposite sexFEMALE TYPE: 46XX.ovaries present,Incr.secretion of androgens,masculaniz ofext.genitalia from enlarged clitoris to compl.male genitalia(partial fusion of lab.majoragiving scrotal appearance)chromatin +veMALE TYPE: 46XY.testes present,Dec.sec of androgens,paramesonep.remnants presentAIS(Androgen Insensitivity Syndrome):X-linked reccessiveOvaries&uterine tubes absent.Testis present in inguinal or labial regions but no spermatogenesisChromatin –veAndrogen receptors either absent or tissues are insensitive to androgen action
  14. 14. HYPOSPADIAS Incomp fusion of urethral folds— abnormal urethral openings appear on the ventral aspect of penis either near the glans,on penis or near its root. If complete lack of fusion,a sagittal slit is formed along the entire length of penis and scrotum(resembles labia majora)EPISPADIAS Ext.urethral meatus opens on the dorsum of penis. Genital tubercle develops in the region of urorectal septum.A small portion of cloacal cranial to