GENITAL SYSTEMGENITAL SYSTEMThe development of the genital The development of the genital

system comprises the development system comprises the development ofof::

((11 ) )GonadsGonads (primitive sex cells) (primitive sex cells)..((22 ) )Genital ductsGenital ducts..

((33 ) )External genitaliaExternal genitalia..All three components pass through an All three components pass through an

indifferent stageindifferent stage in which they may in which they may develop into either a male or a develop into either a male or a femalefemale . .

GENITAL SYSTEMGENITAL SYSTEM

The The Y chromosomeY chromosome causes causes differentiation of the differentiation of the gonadgonad into into testistestis..

The indifferent The indifferent duct systemduct system and and external genitaliaexternal genitalia develop under the develop under the influence of influence of hormoneshormones..

Male and Female morphologic Male and Female morphologic characteristic do not begin to develop characteristic do not begin to develop until the until the 77THTH week week

. .INDIFFERENT STAGE OFINDIFFERENT STAGE OF GONADSGONADS

Gonads are derived from Gonads are derived from three sourcesthree sources: :

((aa ) )MesotheliumMesothelium )mesodermal )mesodermal epithelium ( lining the posterior epithelium ( lining the posterior abdominal wallabdominal wall..

((bb ) )Mesenchyme Mesenchyme )embryonic )embryonic connective tissue(connective tissue(..

C) C) Primordial germ cellsPrimordial germ cells..

GENITAL RIDGEGENITAL RIDGEIt appears during the It appears during the fifthfifth

week as a pair of week as a pair of longitudinal ridges, the longitudinal ridges, the genitalgenital (gonadal(gonadal ridges)ridges) on the medial side of the on the medial side of the mesonephrosmesonephros..

They are formed by They are formed by proliferation of proliferation of epithelium epithelium (mesothelium)and (mesothelium)and condensation of condensation of underlying mesenchymeunderlying mesenchyme..

PRIMITIVE SEX CORDSPRIMITIVE SEX CORDSThey are formed from They are formed from

epithelial cells which epithelial cells which penetrate the underlying penetrate the underlying mesenchyme and form a mesenchyme and form a number of irregularly number of irregularly shaped cordsshaped cords..

In both male and female In both male and female embryos these cords are embryos these cords are connected to the surface connected to the surface epitheliumepithelium..

PRIMORDIAL GERM CELLSPRIMORDIAL GERM CELLS

These primitive sex These primitive sex cells appear early in cells appear early in the the fourth weekfourth week among among the endodermal cells the endodermal cells in the wall of thein the wall of the yolk yolk sac sac close to the close to the allantoisallantois..

PRIMORDIAL GERM CELLSPRIMORDIAL GERM CELLS

They migrate along They migrate along the dorsal mesentery the dorsal mesentery of the hind gut to the of the hind gut to the gonadal ridgesgonadal ridges..

They invade the They invade the underlying underlying mesenchyme of the mesenchyme of the genital ridges in the genital ridges in the six weeksix week and are and are incorporated in the incorporated in the primary sex cordsprimary sex cords..

PRIMORDIAL GERM CELLSPRIMORDIAL GERM CELLS

If they If they fail to reach fail to reach the ridges, the ridges, the the gonad remain gonad remain indifferent or is indifferent or is absentabsent..

So they have an So they have an inductive influenceinductive influence on development of on development of the gonad into the gonad into ovary or testisovary or testis..

INDIFFERENT GONADINDIFFERENT GONADThe indifferent gonad The indifferent gonad

consists of an consists of an external external cortexcortex and and internal internal medullamedulla..

In embryos with In embryos with XXXX sex sex chromosomes, the chromosomes, the cortexcortex differentiates into the differentiates into the ovaryovary and the medulla and the medulla regressesregresses..

In embryos with an In embryos with an XYXY sex sex chromosomes, the chromosomes, the medulla medulla differentiates into differentiates into a a testis testis and the cortex and the cortex regressesregresses . .

SEX DETERMINATIONSEX DETERMINATION11 . .The sex of the embryo is The sex of the embryo is

determined genetically at the time of determined genetically at the time of fertilization depending upon the fertilization depending upon the sperm (X or Y ) fertilizing the X ovumsperm (X or Y ) fertilizing the X ovum..

22 . .Gonads acquire male or female Gonads acquire male or female morphological characteristics about morphological characteristics about the the seventh weekseventh week of development of development..

SEX DETERMINATIONSEX DETERMINATION

The key to this sexual differentiation The key to this sexual differentiation is the is the Y chromosomeY chromosome..

The short arm of this chromosome The short arm of this chromosome contains contains SRYSRY (sex determining region (sex determining region on y ) on y ) genegene..

The protein product of this gene is The protein product of this gene is the the TDFTDF (testis determining factor ) (testis determining factor ) that acts on the medulla of the that acts on the medulla of the indifferent gonadindifferent gonad..

TDFTDF

It causesIt causes::((aa ) )development of the development of the

testis testis )medullary ( cords)medullary ( cords..((bb ) )formation of formation of tunicatunica

albugineaalbuginea..C) failure of the C) failure of the

cortical cords (ovary) cortical cords (ovary) to developto develop..

in its absence female in its absence female development is development is establishedestablished..

SEX DIFFERENTIATIONSEX DIFFERENTIATION((33 ) )The differentiated gonad will The differentiated gonad will

determine the type of sexual determine the type of sexual differentiation in the differentiation in the genital ductsgenital ducts and and external genitaliaexternal genitalia through the through the secretion of hormonessecretion of hormones..

TUNICA ALBUGINEATUNICA ALBUGINEAIt is a dense layer of It is a dense layer of

fibrous tissue which fibrous tissue which separates the testis separates the testis ((seminiferous cordsseminiferous cords) ) from the surface from the surface epitheliumepithelium..

Its development is the Its development is the characteristic and characteristic and diagnostic feature of diagnostic feature of testicular development testicular development in the fetusin the fetus..

MEDULLARY )TESTIS( CORDSMEDULLARY )TESTIS( CORDS

They are the primary They are the primary sex cords which sex cords which condense and extend condense and extend into the medullainto the medulla . .

TESTIS CORDS TESTIS CORDS )SEMINIFEROUS CORDS()SEMINIFEROUS CORDS(

They become They become horse shoehorse shoe shaped in the shaped in the fourthfourth monthmonth..

The The seminiferous cordsseminiferous cords develop intodevelop into: :

Seminiferous tubulesSeminiferous tubules..Tubuli rectiTubuli recti..

Rete testisRete testis..

RETE TESTISRETE TESTIS

They are a They are a networknetwork of tiny strands that of tiny strands that result from the result from the break up of the break up of the seminiferous cordsseminiferous cords at the hilum of the at the hilum of the gonadgonad..

Their extremities Their extremities become continuous become continuous with those of the with those of the cordscords..

SEMINIFEROUS TUBULESSEMINIFEROUS TUBULESThe wall of the tubules The wall of the tubules

containcontain: : ((11 ) )Sustentacular cells of Sustentacular cells of

SertoliSertoli They are derived from the They are derived from the

surface epithelium of the surface epithelium of the gonad.They secrete gonad.They secrete Anti ’ Anti ’ Mullerian HormoneMullerian Hormone (AMH)(AMH) which suppresses the which suppresses the development of development of paramesonephric (mullerian) paramesonephric (mullerian) ducts.The hormone decreases ducts.The hormone decreases

after pubertyafter puberty..

SEMINIFEROUS TUBULESSEMINIFEROUS TUBULES

((22 ) )Spermatogonia :Spermatogonia : primordial sperm primordial sperm cells derived cells derived from the from the primordial germ primordial germ cellscells..

INTERSTITIAL CELLS OF INTERSTITIAL CELLS OF LEYDIGLEYDIG

These cells are derivedThese cells are derived from the from the original original mesenchymemesenchyme of the of the

genital ridgegenital ridge . . They They lielie between the between the

seminiferous cordsseminiferous cords..They produce They produce

testosterone testosterone andand androstendioneandrostendione (androgenic hormones) (androgenic hormones) by the by the eight weekeight week..

INTERSTITIAL CELLS OF INTERSTITIAL CELLS OF LEYDIGLEYDIG

The testis becomes The testis becomes able to influence able to influence sexual sexual differentiation of differentiation of the genital ducts the genital ducts and external and external genitaliagenitalia..

Testosterone is Testosterone is stimulated by stimulated by ((HCGHCG) which ) which reaches a peak reaches a peak between (between (88thth –12 –12thth weeksweeks..

MATURATION OF THE TESTISMATURATION OF THE TESTISThe The seminiferous tubulesseminiferous tubules

join the rete testisjoin the rete testis..The The rete testisrete testis are joined are joined

to 15 –20 efferent to 15 –20 efferent ductules ductules (mesonephric (mesonephric tubules)tubules)..

These ductules are These ductules are connected to the connected to the mesonephric mesonephric duct( duct( ductus deferensductus deferens) = ) = ductus epididymisductus epididymis..

MATURATION OF THE TESTISMATURATION OF THE TESTISThe surface The surface

epithelium is epithelium is flattened and forms flattened and forms the mesothelium on the mesothelium on the external surface the external surface of the adult testisof the adult testis..

The seminiferous The seminiferous cords remain solid cords remain solid until puberty when until puberty when they acquire a lumen they acquire a lumen and become tubulesand become tubules..

INDIFFERENT STAGE OF INDIFFERENT STAGE OF GENITAL DUCTSGENITAL DUCTS

Between(4Between(4thth and 5 and 5thth ) weeks, ) weeks, both male and female embryos both male and female embryos have two pair of genital ductshave two pair of genital ducts: :

11 . .Mesonephric (Wolffian)Mesonephric (Wolffian) ductsducts . .

They play an important role in They play an important role in the development of male the development of male genital systemgenital system..

22 . .Paramesonephric (Mullerian) Paramesonephric (Mullerian) ductsducts..

They are important in the They are important in the development of female genital development of female genital systemsystem..

MESONEPHRIC DUCTSMESONEPHRIC DUCTSUnder the influence of Under the influence of

testosterone the testosterone the mesonephric duct will mesonephric duct will formform::

11 . .EpidydimisEpidydimis : :It is the It is the proximal proximal highly highly

convoluted part of the convoluted part of the ductduct..

22 . .Ductus DeferensDuctus Deferens: : It is the part of the duct It is the part of the duct

distaldistal to the epididymis. to the epididymis. It acquires a thick It acquires a thick investment of smooth investment of smooth musclemuscle..

MESONEPHRIC DUCTSMESONEPHRIC DUCTS

33 . .Seminal VesiclesSeminal VesiclesThey are lateral They are lateral

outgrowth from the outgrowth from the caudal endcaudal end of each of each mesonephric ductmesonephric duct..Their secretion Their secretion nourish the spermsnourish the sperms..

MESONEPHRIC DUCTSMESONEPHRIC DUCTS44.. Ejaculatory DuctEjaculatory Duct::

It is the part of the It is the part of the mesonephric duct that mesonephric duct that lies between the duct of lies between the duct of seminal vesicle and the seminal vesicle and the urethraurethra..

MESONEPHRIC DUCTSMESONEPHRIC DUCTS

Efferent Efferent Ductules Ductules of the of the

testistestis : : Formed from the Formed from the

persisting persisting excretory excretory mesonephric mesonephric tubulestubules..

REMMNANT OF MESONEPHRIC REMMNANT OF MESONEPHRIC DUCTSDUCTS

11 . .Appendix of Appendix of epididymisepididymis..

The most cranial The most cranial part of the ductpart of the duct..

22 . .ParaydidymisParaydidymis Remnants of tubules Remnants of tubules

at the caudal pole at the caudal pole of the testis which of the testis which do not join the cords do not join the cords of the rete testisof the rete testis..

PARAMESONEPHRIC DUCTSPARAMESONEPHRIC DUCTS

MIS MIS produced by produced by Sertoli cells of the Sertoli cells of the testes causes the testes causes the paramesonephric ducts paramesonephric ducts to disappear by to disappear by epithelial epithelial mesenchymal mesenchymal transformationtransformation..

Their remnant is the Their remnant is the appendix of testisappendix of testis..

PROSTSTE GLANDPROSTSTE GLAND

It is multiple It is multiple endodermal endodermal outgrowthsoutgrowths from from the the prostatic prostatic urethraurethra..

It grows into the It grows into the surrounding surrounding mesenchyme that mesenchyme that will form the dense will form the dense stroma and the stroma and the smooth muscle of smooth muscle of the glandthe gland..

BULBOURETHRAL GLANDSBULBOURETHRAL GLANDS

They are pea They are pea sized structures sized structures that develop from that develop from the the spongy part of spongy part of the urethrathe urethra..

The adjacent The adjacent mesenchyme will mesenchyme will form the stroma form the stroma and smooth and smooth muscles of the muscles of the glandsglands..

INGUINAL CANALINGUINAL CANAL

It is the pathway It is the pathway for the descend of for the descend of the testis from the the testis from the intra abdominal intra abdominal position to the position to the scrotumscrotum..

It develops in both It develops in both sexes because of sexes because of the indifferent the indifferent stage of the sexual stage of the sexual developmentdevelopment..

INGUINAL CANALINGUINAL CANALA band of mesenchyme A band of mesenchyme

(Gubernaculum)(Gubernaculum) extends from the extends from the inferior pole of the inferior pole of the gonad to the gonad to the labioscrotal swellinglabioscrotal swelling..

This ligament passes This ligament passes obliquely on each side obliquely on each side of the abdomen through of the abdomen through the developing anterior the developing anterior abdominal wall at the abdominal wall at the site of the future site of the future inguinal canalinguinal canal..

DESCENT OF THE TESTISDESCENT OF THE TESTIS

The descent of the The descent of the testes through the testes through the inguinal canals into inguinal canals into the scrotum begins the scrotum begins during the during the 2626thth week week..

It takes It takes (2 -3) days(2 -3) days..About (97%) of full About (97%) of full

term new born boys term new born boys have both testes in have both testes in the scrotumthe scrotum..

DESCENT OF THE TESTISDESCENT OF THE TESTIS

It is due toIt is due to::((11 ) )Enlargement Enlargement

of the testes and of the testes and atrophy of the atrophy of the mesonephric mesonephric kidneykidney..

((22 ) )AtrophyAtrophy of the of the paramesonephric paramesonephric ductsducts..

((33 ) )PROCESSUS VAGINALISPROCESSUS VAGINALIS

It is an evagination of It is an evagination of peritoneum that peritoneum that develop ventral to the develop ventral to the gubernaculumgubernaculum . .

It herniates through It herniates through the abdominal wall the abdominal wall along the path along the path formed by the formed by the gubernaculumgubernaculum..

PROCESSUS VAGINALISPROCESSUS VAGINALISIt carries extensions of It carries extensions of

the layers of the the layers of the abdominal wall before it abdominal wall before it which forms the layers of which forms the layers of the inguinal canalthe inguinal canal..

It produces an opening in It produces an opening in the fascia transversalis the fascia transversalis that becomes the that becomes the deep deep inguinal ringinguinal ring..

The opening formed in The opening formed in the external oblique the external oblique aponeurosis becomes theaponeurosis becomes the superficial inguinal ringsuperficial inguinal ring..

DESCENT OF THE TESTESDESCENT OF THE TESTES

By By (26(26thth ) weeks ) weeks, the , the testes have descended testes have descended retroperitoneally to retroperitoneally to the the deep inguinal ringdeep inguinal ring..

It is a relative It is a relative movement because of movement because of the growth of the the growth of the cranial part of the cranial part of the abdominal cavity away abdominal cavity away from the caudal partfrom the caudal part..

FACTORS CONTROLLINGFACTORS CONTROLLING DESCENT OF TESTESDESCENT OF TESTES

11 . .AndrogensAndrogens (e.g. (e.g. testosterone) produced testosterone) produced by the fetal testesby the fetal testes..

22.. GubernaculumGubernaculum: : Its role is uncertainIts role is uncertain . .

It can guide the descentIt can guide the descent ..

The increase of the The increase of the abdominal pressure can abdominal pressure can produces passage produces passage through the inguinal through the inguinal canalcanal..

DESCENT OF TESTESDESCENT OF TESTES

The descended The descended testes carry their testes carry their ductus deferensductus deferens and and vessels with themvessels with them. .

Both the testes and Both the testes and ductus deferens ductus deferens become ensheathed become ensheathed by the fascial by the fascial extensions of the extensions of the abdominal wallabdominal wall..

TESTIS WITHIN SCROTUMTESTIS WITHIN SCROTUM

Within the scrotum, the Within the scrotum, the testis projects into the testis projects into the distal end of the distal end of the processus vaginalisprocessus vaginalis..

During the intrauterine During the intrauterine life the connecting stalk life the connecting stalk of the process is of the process is obliterated normally, so obliterated normally, so it isolates the it isolates the tunica tunica vaginalisvaginalis..

The inguinal canal The inguinal canal contracts around the contracts around the spermatic cordspermatic cord . .

CRYPTORCHIDISMCRYPTORCHIDISM

It occurs in up to 30% of It occurs in up to 30% of premature males and in 3 to 4 premature males and in 3 to 4 % of full term males% of full term males..

It can be unilateral or It can be unilateral or bilateralbilateral..

The cause is not well known The cause is not well known but a deficiency of but a deficiency of androgen androgen productionproduction by the fetal testes by the fetal testes is an important factoris an important factor..

COMMON SITESCOMMON SITES

It can be in the It can be in the abdominal cavityabdominal cavity or or along the path of along the path of the testes in the the testes in the inguinal canalinguinal canal . .

The UndescendedThe Undescended testes are testes are histologically histologically normal at birth but normal at birth but failure of failure of development and development and atrophy are atrophy are detected by the end detected by the end of the first yearof the first year..

COMPLICATIONSCOMPLICATIONS

11 . .SterilitySterility if both if both testes are testes are undescendedundescended . .

22 . .Increase in the Increase in the risk of risk of testicular testicular cancercancer (20-44%) (20-44%)..