1) The genital ridges form on the abdominal wall and penetrate the underlying tissue to form primitive sex cords. These early gonads are indifferent. 2) Two types of genital ducts, the paramesonephric and mesonephric ducts, form at the indifferent stage. 3) In males, under the influence of the SRY gene, the primitive sex cords form seminiferous tubules and interstitial cells begin secreting testosterone, developing the testes. The testes descend into the scrotum between 12-33 weeks.

1. Genital System Development

2. FORMATION OF GONADAL
RIDGES/GENITAL RIDGES
Produced on the post.abdominal wall
by the proliferation of epithelium and
the condensation of underlying
mesenchyme

3. FORMATON OF PRIMITIVE SEX
CORDS
Migration of PGCs from the endoderm in the wall of
yolk sac along the dorsal mesentery to the
developing gonad.
During & Before migration Epithelium of genital
ridges undergoes proliferation and penetrate the
underlying mesenchyme to form primitive sex
cords which are connected to surface epithelium.
Gonads at this stage are said to be “INDIFFERENT”
gonad.

4. GENITAL DUCTS AT INDIFFERENT
STAGE
2 Types
Paramesonephric(Mullerian)&Mesonphric(Wolffian)ducts.
PARAMESONEPHRIC:
Lie lateral to the mesonephric
Superiorly continuous with abd.cavity
Inferiorly they cross the mesonephric ducts caudomedially &join with those of
opposite side.
Initially the two are separated from each other by a septum but later they fuse to
form”UTERINE CANAL”that projects into the post.wall of urogenital sinus to
raise a tubercle called”Paramesonephric/Mullerian tubercle”
MESONEPHRIC:
They open on either side of the tubercle into the urogenital sinus

5. DEVELOPMENT OF TESTIS
1)Formation of Testis/Medullary cords:
Under the influence of SRY gene which encodes TDF
2)Formation of tubules of rete testis:
Testis cords break up at the hilum of gland to form these tiny cell strands
3)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 rete
testis
5)Comp.of testis cord:
PGCs& Sustentacular cells
5)Interstitial cells:Derived from mesenchyme of gonadal rdge b/w the testis cords.begin
secretingtestosterone in 8th week.
6)Canalization of cords to form seminiferous tubules:occurs at puberty.s.tubules join tubules of
rete testis which enter the efferent ductules(rmnants of mesonephric sys tubules)
7)Effernt ductules link mesonepphric ducts which develop into ductus deferens

6. DESCENT OF TESTES
Urogenital mesentery suspends testes &mesonephros to post.abd wall
Mesonephros regresses
CAUDAL GENITAL LIGAMENT:Caudal part of mesentery
GUBERNACULUM:Condensation of mesenchyme containing extracellular matrix extending
from the caudal pole of testis.Terminates in the inguinal region b/w differentiating
int&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 caused
by growth of testis
Testis reach the INGUINAL REGION:12weeksINGUINAL CANAL:28weeksSCROTUM:33weeks
Hormones responsible:Androgen&MIS
COVERINGS:1)Reflected part of processus vaginalis forming visceral&parietal layer of
tunica vaginalis.
2)Derived from ant.abd wall through which it passes viz;Int.spermatic
fascia(Transv.fascia)Cremastrc fascia(Int oblique)Ext.sperm fascia(Ext.oblique)Transversus
abd doesn’t contribute any layer
PROCESSUS VAGINALIS:Peritoneal evaginations on each side of midline in ventral
abdominal wall that follows the course of gubernaculum.It forms INGUINAL CANAL
accompanied by fascial&muscular layers of body wall.At birth or shortly thereafter,its
narrow canal connecting it to peritoneal cavity gets obliterated.

7. DEVELOPMENT OF OVARY
Dissociation of prim. sex cords in medulla into irregular cell clusters
Clusters contain PGCs
That later disappear &are replaced by vascular stroma that forms
ovarian medulla
FORM.OF CORTICAL CORDS:
Unlike in males, surface epithelium undergoes proliferation to form
cortical cords which penetrate the underlying mesenchyme
BREAKING OF CORDS INTO ISOLATED CELL CLUSTERS:
That surround 1 or more PGCs
FATE OF PGCs: Oogonia
FATE OF Epithelium.derived cells: Follicular cells

8. DESCENT OF OVARIES
Considerably less
FINAL POSITION:Just below the rim of true pelvis
Cranial genital ligament:Suspensory lig.of ovary
Caudal genital ligament:Lig.of ovary proper&Round
ligament of uterus(extending to labia majora)

9. GENITAL DUCTS
MALE FEMALE
EPIGENITAL TUBULES:Remnants CRANIAL VERTICAL PART :
of excretory tubules of develops into uterine tube
mesonephric system that join the MIDDLE HORIZONTAL PART
rete testis to form efferent CAUDAL VERTICAL PART : Fuses
ductules with its partner from the opposite
side to form uterine canal
PARAGENITAL BROAD LIGAMENT : transverse
TUBULES:Exc.tubules along the pelvic fold that extends from the
caudal pole of testis that don’t join lateral sides of fused
rete testis paramesonephric ducts towards
the wall of pelvis
Up border : Contains uterine tubes
with ovaries on posterior surface

10. VAGINA
FORMATION OF SINOVAGINAL BULBS:Shortly after the form.of
paramesonephric tubercle,evaginations appear from the pelvic part of
urogenital sinus
FORMATION OF VAGINAL PLATE: Formed by the fusion of sinovaginal bulbs
PROLIFERATION: Occurs in cranial region increasing the distance b/w
uterus&urogenital sinus
CANALIZATION
DUAL ORIGIN:1)Wing like expansions vaginal fornices.Paramesonephric in
origin.Originate from uterine canal2)Remaining part:From urogenital sinus
HYMEN:Forms during perinatal like as a small opening through which vagina
remains separated from urogenital sinus.Made up of epithelial cells and thin
layer of vaginal cells

11. EXTERNAL GENITALIA
INDIFFERENT STAGE:
Mesenchymal cells from the prim.streak migrate around the cloacal
memb and raise slight elevations called”CLOACAL FOLDS”
Cloacal folds:ANT:Urethral folds,POST:Anal folds
GENITAL TUBERCLE:Formed by fusion of urethral folds cranially
GENITAL SWELLINGS:Appear lateral to urethral swellings.Forms scrotal
swellings in males&Labia majora in females

12. DEVELOPMENT OF EXT.GENITALIA
MALE FEMALE
Genital tubercle elongates to form Genital tubercle elongates to
”PHALLUS” form”Clitoris”
Elongation of phallus is Urethral folds don’t fuse rather
accompanied by forward movement form labia minora
of urethral folds
Epi.of urethral groove forms Genital swellings form labia majora
urethral plate
Urethral folds fuse thus closing off Urethral groove forms vestibule
urethral plate thus forming PENILE
URETHRA
Ur.groove doesn’t extend into distal During early stages of
part 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 gestation
Distal most part of urethra is formed
by the ectodermal cell proliferation
from the tip of glans into the phallus

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:XO
Short stature,Webbed neck,PCCR(Palate arched,Chest shield like,Cardiac&Renal
abnormalities)
HERMAPHRODITISM:Raised as females,Phenotype 46,XX.Genitalia ambiguus,female
like,possess both ovarian&testicular tissue.
PSEDOHERMAPHRODITISM: Genotype is masked by phenotype that closely resembles
that of opposite sex
FEMALE TYPE: 46XX.ovaries present,Incr.secretion of androgens,masculaniz of
ext.genitalia from enlarged clitoris to compl.male genitalia(partial fusion of lab.majora
giving scrotal appearance)chromatin +ve
MALE TYPE: 46XY.testes present,Dec.sec of androgens,paramesonep.remnants present
AIS(Androgen Insensitivity Syndrome):
X-linked reccessive
Ovaries&uterine tubes absent.
Testis present in inguinal or labial regions but no spermatogenesis
Chromatin –ve
Androgen receptors either absent or tissues are insensitive to androgen action

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 memb.is cranial to