10.development of urogenital system

Development of Development of Urogenital SystemUrogenital System

• Functionally, the urogenital system can be divided into two entirely different components: the urinary system and the genital system.

• Embryologically and anatomically, however, they are intimately related.

• Both develop from a common mesodermal ridge (intermediate mesoderm) and the cloaca.

• Initially the excretory ducts of both systems enter a common cavity, the cloaca.

Development of Urinary SystemDevelopment of Urinary System

Development of Urinary SystemDevelopment of Urinary System Urinary system is derived from the Urinary system is derived from the

intermediate mesoderm intermediate mesoderm and and cloaca.cloaca.

Epithelium of the urinary system is derived Epithelium of the urinary system is derived from the from the intermediate mesodermintermediate mesoderm..

After the After the foldingfolding of embryonic disc and of embryonic disc and formation of formation of peritoneal cavityperitoneal cavity, the , the intermediate mesodermintermediate mesoderm forms a bulging forms a bulging on the posterior abdominal wall called on the posterior abdominal wall called nephrogenic cordsnephrogenic cords or or urogenital ridgeurogenital ridge..

It is covered by epithelium lining the It is covered by epithelium lining the peritoneal cavity (peritoneal cavity (coelomic epitheliumcoelomic epithelium).).

It extends from It extends from cervicalcervical to to sacral sacral region.region.

At varying stage of development, a number of At varying stage of development, a number of important structures are formed in relation to important structures are formed in relation to nephrogenic cordnephrogenic cord as follows: as follows:

Excretory tubulesExcretory tubules Mesonephric ductMesonephric duct Paramesonephric ductParamesonephric duct GonadGonad

CloacaCloaca CloacaCloaca is subdivided into the ventral is subdivided into the ventral

primitive urogenital sinusprimitive urogenital sinus and dorsal and dorsal primitive rectumprimitive rectum by the by the urorectal septumurorectal septum..

Primitive urogenital sinus is subdivided into a Primitive urogenital sinus is subdivided into a cranial part, called cranial part, called vesico-urethral canalvesico-urethral canal and a caudal part, called the and a caudal part, called the definitive definitive urogenital sinusurogenital sinus..

The openings of The openings of mesonephric ductsmesonephric ducts lie at lie at the junction of these two subdivisions.the junction of these two subdivisions.

The definitive urogenital sinus is further The definitive urogenital sinus is further divided into a cranial divided into a cranial pelvic partpelvic part and a caudal and a caudal phallic partphallic part..

Development of kidney Development of kidney systemssystems

Three kidney systems are formed in a cranial-Three kidney systems are formed in a cranial-to-caudal sequence during intrauterine life in to-caudal sequence during intrauterine life in humans: humans:

- Pronephros Pronephros - Mesonephros, and Mesonephros, and - Metanephros Metanephros

The The first first of these systems is rudimentary and of these systems is rudimentary and

nonfunctional; the nonfunctional; the secondsecond may function for a may function for a short time during the early fetal period; the short time during the early fetal period; the thirdthird forms the permanent kidney. forms the permanent kidney.

PronephrosPronephros

At the beginning of the At the beginning of the fourth weekfourth week, the , the pronephrospronephros is represented by 7 to 10 is represented by 7 to 10 solid cell groups in the solid cell groups in the cervical regioncervical region..

These groups form vestigial excretory These groups form vestigial excretory units, units, nephrotomesnephrotomes, that regress before , that regress before more caudal ones are formed. more caudal ones are formed.

By the end of the fourth week, the By the end of the fourth week, the pronephric system will pronephric system will disappeardisappear..

MesonephrosMesonephros The The mesonephrosmesonephros and and mesonephric ductsmesonephric ducts are are

derived from derived from intermediate mesodermintermediate mesoderm from from upper upper thoracicthoracic to to upper lumbar (L3)upper lumbar (L3) segments. segments.

Early in the 4Early in the 4thth week of development, the first week of development, the first excretory tubulesexcretory tubules of the mesonephros appear. of the mesonephros appear.

They lengthen rapidly, form an They lengthen rapidly, form an S-shaped loopS-shaped loop, and , and acquire a tuft of capillaries that will form a acquire a tuft of capillaries that will form a glomerulus glomerulus at their medial extremity. at their medial extremity.

Around the glomerulus, the tubules form Around the glomerulus, the tubules form BowmanBowman’’s capsules capsule, and together these structures , and together these structures constitute a constitute a renal corpusclerenal corpuscle. .

Laterally, the tubule enters the longitudinal Laterally, the tubule enters the longitudinal collecting duct known as the collecting duct known as the mesonephric mesonephric or or wolffian ductwolffian duct..

While caudal tubules are still differentiating, While caudal tubules are still differentiating, cranial tubules and glomeruli show cranial tubules and glomeruli show degenerative changes, and by the end of the degenerative changes, and by the end of the 22ndnd month month, the majority have disappeared. , the majority have disappeared.

In the male, a few of the caudal tubules and In the male, a few of the caudal tubules and the the mesonephric ductmesonephric duct persist and persist and participate in formation of the genital system, participate in formation of the genital system, but they disappear in the female.but they disappear in the female.

Metanephros: The Metanephros: The Definitive KidneyDefinitive Kidney

The third urinary organ, the metanephros The third urinary organ, the metanephros or permanent kidney, appears in the 5or permanent kidney, appears in the 5thth week. week.

Its excretory units develop from Its excretory units develop from metanephric mesoderm in the same metanephric mesoderm in the same manner as in the mesonephric system. manner as in the mesonephric system.

The development of the duct system The development of the duct system differs from that of the other kidney differs from that of the other kidney systems.systems.

Formation of Collecting Formation of Collecting SystemSystem

Collecting ducts of the permanent kidney develop Collecting ducts of the permanent kidney develop from the from the ureteric budureteric bud, an outgrowth of the , an outgrowth of the mesonephric ductmesonephric duct close to its entrance to the close to its entrance to the cloaca. cloaca.

The bud penetrates the The bud penetrates the metanephric tissuemetanephric tissue, which is , which is molded over its distal end as a molded over its distal end as a capcap. .

The The ureteric budureteric bud form a dilation called form a dilation called ampullaampulla. The . The ampulla devides repeatedly. ampulla devides repeatedly.

First 3-5 generations of branches fuse to form First 3-5 generations of branches fuse to form pelvispelvis of kidney.of kidney.

Next division - Next division - major calycesmajor calyces and further divisions - and further divisions - minor calycesminor calyces and and collecting tubules collecting tubules (1 to 3 (1 to 3 millions).millions).

These buds continue to subdivide until These buds continue to subdivide until 12 or 12 or moremore generations of tubules have formed. generations of tubules have formed.

During further development, collecting During further development, collecting tubules of the fifth and successive tubules of the fifth and successive generations elongate considerably and generations elongate considerably and converge on the minor calyx, forming the converge on the minor calyx, forming the renal pyramidrenal pyramid. .

The The ureteric budureteric bud gives rise to the gives rise to the ureterureter, , the the renal pelvisrenal pelvis, the , the majormajor and and minor minor calycescalyces, and approximately 1 to 3 million , and approximately 1 to 3 million collecting tubulescollecting tubules..

Formation of Excretory Formation of Excretory SystemSystem

Each collecting tubule is covered by Each collecting tubule is covered by Metanephric capMetanephric cap..

Under the inductive influence of tubule, cells Under the inductive influence of tubule, cells of tissue cap forms of tissue cap forms renal vesicles, renal vesicles, which in which in turn is converted into turn is converted into ‘‘SS’’ shaped tubule shaped tubule..

Capillaries grow into the pocket at one end Capillaries grow into the pocket at one end of the S and differentiate into of the S and differentiate into glomeruliglomeruli. .

These tubules, together with their glomeruli, These tubules, together with their glomeruli, form form nephronsnephrons, or excretory units., or excretory units.

The proximal end of each nephron forms The proximal end of each nephron forms BowmanBowman’’s capsules capsule, which is deeply indented , which is deeply indented by a glomerulus. by a glomerulus.

The distal end forms an open connection with The distal end forms an open connection with the collecting tubules. the collecting tubules.

Continuous lengthening of the excretory Continuous lengthening of the excretory tubule results in formation of the tubule results in formation of the proximal proximal convoluted tubuleconvoluted tubule, , loop of Henleloop of Henle, and , and distal convoluted tubuledistal convoluted tubule. .

Hence, the kidney develops from Hence, the kidney develops from two sourcestwo sources: :

1)1)Metanephric mesodermMetanephric mesoderm, which , which provides provides excretory unitsexcretory units and and

2)2)Ureteric budUreteric bud, which gives rise to , which gives rise to the the collecting system.collecting system.

Ascent of kidneyAscent of kidney Definitive human kidney develops from Definitive human kidney develops from

the the metanephrosmetanephros in the in the sacral regionsacral region..

Ascends due to the differential growth of Ascends due to the differential growth of the abdominal wall.the abdominal wall.

Final position is in the Final position is in the lumbar regionlumbar region..

The The hilumhilum faces medially. faces medially.

The metanephros, at first, receives blood The metanephros, at first, receives blood supply from supply from lateral sacral arterieslateral sacral arteries, but , but with its ascent, branch of the with its ascent, branch of the aortaaorta at the at the level of level of L2L2 take over the supply. take over the supply.

Congenital Congenital anomaliesanomalies AgenesisAgenesis

DuplicationDuplication

Anomalies in shapeAnomalies in shape- Horse shoe kidneyHorse shoe kidney- Pancake kidneyPancake kidney- LobulatedLobulated

Anomalies in positionAnomalies in position- Present in sacral regionPresent in sacral region- May be in thoracic regionMay be in thoracic region

Congenital polycystic Congenital polycystic kidneykidney

Development of UreterDevelopment of Ureter

Derived from the part of Derived from the part of ureteric ureteric budbud that lies between that lies between pelvispelvis of of kidney and kidney and vesico-urethral canalvesico-urethral canal i.e., intermediate mesoderm.i.e., intermediate mesoderm.

The The connective tissueconnective tissue & & musclesmuscles are derived from the are derived from the intermediate intermediate mesodermmesoderm of the of the metanephric metanephric capcap..

Congenital anomaliesCongenital anomalies

Ureter may be duplicated partially Ureter may be duplicated partially or completely.or completely.

Abnormal opening of ureter.Abnormal opening of ureter.

Post- caval ureter - Right sided Post- caval ureter - Right sided hydronephrosis.hydronephrosis.

Development of Urinary Development of Urinary bladderbladder

EpitheliumEpithelium of the bladderof the bladder –– develops from the develops from the cranial part of the vesico-urethral canal cranial part of the vesico-urethral canal (endoderm(endoderm).).

Epithelium of trigoneEpithelium of trigone –– derived from the derived from the absorbed mesonephric ducts (absorbed mesonephric ducts (mesodermmesoderm))

Muscular and serous wallsMuscular and serous walls –– derived from derived from splanchnopleuric splanchnopleuric mesodermmesoderm..

Initially, bladder is continuous with Initially, bladder is continuous with allantoisallantois, , but when the lumen of allantois is obliterated, a but when the lumen of allantois is obliterated, a thick fibrous cord, the thick fibrous cord, the urachus urachus remains.remains.It connects the apex of bladder to umbilicus, in It connects the apex of bladder to umbilicus, in adult called as adult called as median umbilical ligamentmedian umbilical ligament..

The caudal portions of the The caudal portions of the mesonephric ductsmesonephric ducts are are absorbed into the wall of the urinary bladder.absorbed into the wall of the urinary bladder.

Consequently, the Consequently, the uretersureters, initially outgrowth from , initially outgrowth from the mesonephric ducts, enter the bladder separately.the mesonephric ducts, enter the bladder separately.

As kidneys ascend, the orifices of the As kidneys ascend, the orifices of the uretersureters move move farther cranially; those of the farther cranially; those of the mesonephric ductsmesonephric ducts move close together to enter the move close together to enter the prostatic urethraprostatic urethra and in males becomes the and in males becomes the ejaculatory ductsejaculatory ducts..

Since both the mesonephric ducts and ureters originate in the mesoderm, the mucosa of the bladder formed by incorporation of the ducts (the trigone of the bladder) is also mesodermal.

With time, the mesodermal lining of the trigone is replaced by endodermal epithelium, so that finally, the inside of the bladder is completely lined with endodermal epithelium.


Urachal fistula, urachal cyst or Urachal fistula, urachal cyst or sinus:sinus:

The lumen is persist in the urachus.The lumen is persist in the urachus.

Extrophy of bladder or ectopia Extrophy of bladder or ectopia vesicaevesicae

Development of UrethraDevelopment of Urethra Male Urethra:Male Urethra:a.a. From urinary bladder upto the openings of From urinary bladder upto the openings of

ejaculatory ductsejaculatory ducts –– derived from caudal part of derived from caudal part of vesicourethral canalvesicourethral canal. Posterior wall derived . Posterior wall derived from absorbed from absorbed mesonephric ducts.mesonephric ducts.

b.b. Rest of Rest of prostatic urethraprostatic urethra and and membranous membranous urethraurethra - derived from the - derived from the pelvic part of pelvic part of definitive urogenital sinus.definitive urogenital sinus.

c.c. Penile partPenile part of the urethra - derived from the of the urethra - derived from the phallic part of definitive urogenital sinusphallic part of definitive urogenital sinus..

d.d. The most terminal part - derived the The most terminal part - derived the ECTODERMECTODERM

Female urethraFemale urethra- Derived from the Derived from the caudal part of vesico-caudal part of vesico-

urethral canalurethral canal..

- As it corresponds to the prostatic part of As it corresponds to the prostatic part of male urethra, may receive slight male urethra, may receive slight contribution from contribution from pelvic part of pelvic part of urogenital sinus.urogenital sinus.

Development of ProstateDevelopment of Prostate Develops from large number of Develops from large number of budsbuds arising from arising from

the epithelium of the the epithelium of the prostatic urethra, prostatic urethra, i.e. caudal i.e. caudal part of the vesico-urethral canal and from pelvic part of the vesico-urethral canal and from pelvic part of definitive urogenital sinus.part of definitive urogenital sinus.

Buds arising from the Buds arising from the mesodermalmesodermal part of part of prostatic urethra (posterior wall above the openings prostatic urethra (posterior wall above the openings of ejaculatory ducts) form of ejaculatory ducts) form inner glandular zoneinner glandular zone..

Buds arising from the rest of prostatic urethra Buds arising from the rest of prostatic urethra ((endodermendoderm) form the ) form the outer glandular zoneouter glandular zone..

MusclesMuscles and and connective tissueconnective tissue are derived from are derived from surrounding mesenchyme, which also form capsule surrounding mesenchyme, which also form capsule of the gland.of the gland.

Inner zoneInner zone : Benign prostatic hypertrophy : Benign prostatic hypertrophy Outer zoneOuter zone : Carcinoma : Carcinoma

Female homologues of Female homologues of ProstateProstate

Urethral glandUrethral gland –– developed from buds developed from buds arising from the caudal part of vesico-arising from the caudal part of vesico-urethral canal.urethral canal.

Paraurethral glands of SkeneParaurethral glands of Skene –– develops develops from buds arising from the urogenital sinusfrom buds arising from the urogenital sinus

Development of Development of Genital systemGenital system

Paramesonephric duct or Paramesonephric duct or Mullerian ductMullerian duct

The The paramesonephric ductparamesonephric duct arises as a arises as a longitudinal invagination of the longitudinal invagination of the coelomic coelomic epitheliumepithelium of of nephrogenic cordnephrogenic cord..

Cranially, the duct opens into the abdominal Cranially, the duct opens into the abdominal cavity with a funnel like structure.cavity with a funnel like structure.

Caudally, it first runs Caudally, it first runs laterallateral to the to the mesonephric mesonephric ductduct, then crosses it ventrally to grow , then crosses it ventrally to grow mediallymedially..

Then the two ducts meet and fuse in the mid line Then the two ducts meet and fuse in the mid line to form to form Utero-vaginal canalUtero-vaginal canal ( (uterine canaluterine canal).).

The caudal end of this canal projects into the The caudal end of this canal projects into the posterior wall of posterior wall of definitive urogenital sinusdefinitive urogenital sinus..

Development of Uterus and Uterine Development of Uterus and Uterine tubestubes

EpitheliumEpithelium of the uterus : develops from the fused of the uterus : develops from the fused paramesonephric ductsparamesonephric ducts ( ( utero-vaginal canalutero-vaginal canal).).

MyometriumMyometrium : derived from surrounding : derived from surrounding mesodermmesoderm..

FundusFundus of uterus : formed by partial merging of the of uterus : formed by partial merging of the unfused horizontal parts of the unfused horizontal parts of the two two paramesonephric ductsparamesonephric ducts within the within the myometriummyometrium..

Uterine tubesUterine tubes : develop from : develop from unfusedunfused parts of parts of paramesonephric ductsparamesonephric ducts..

The point of invagination into The point of invagination into coelomic epitheliumcoelomic epithelium remains as the abdominal opening, where remains as the abdominal opening, where fimbriafimbria are are formed.formed.


Uterus:Uterus: Complete duplication of uterus (Complete duplication of uterus (uterus uterus

didelphysdidelphys) or partial duplication ) or partial duplication ((bicornuate uterusbicornuate uterus))

Unicornuate uterusUnicornuate uterus

Uterine tubes:Uterine tubes: Absent on one or both sidesAbsent on one or both sides Partially or completely duplicated on one or Partially or completely duplicated on one or

both sidesboth sides Atresia of the tubesAtresia of the tubes

Development of VaginaDevelopment of Vagina Shortly after the solid tip of the Shortly after the solid tip of the

paramesonephric ductsparamesonephric ducts reaches the reaches the urogenital sinusurogenital sinus, two endodermal swellings , two endodermal swellings called called sinovaginal bulbssinovaginal bulbs, grow out from the , grow out from the pelvic part of the sinus. pelvic part of the sinus.

These These sinovaginal bulbssinovaginal bulbs, proliferate and fuse , proliferate and fuse to form a solid to form a solid vaginal platevaginal plate..

By the fifth month, the vaginal outgrowth is By the fifth month, the vaginal outgrowth is entirely entirely canalizedcanalized. .

The wing-like expansions of the vagina around The wing-like expansions of the vagina around the end of the uterus, the the end of the uterus, the vaginal fornicesvaginal fornices, are , are of of paramesonephric paramesonephric origin.origin.

Thus, the vagina has a Thus, the vagina has a dual origindual origin, with the , with the upper portion derived from the upper portion derived from the uterine canaluterine canal and the lower portion derived from the and the lower portion derived from the urogenital sinusurogenital sinus..

The lumen of the vagina remains separated from The lumen of the vagina remains separated from that of the urogenital sinus by a thin tissue that of the urogenital sinus by a thin tissue plate, the plate, the hymenhymen..

Both surfaces of hymen are lined by Both surfaces of hymen are lined by endodermendoderm..

Congenital anomaliesCongenital anomalies Duplication of Duplication of

vaginavagina

Vaginal atresiaVaginal atresia

Rectovaginal Rectovaginal fistula or fistula or vesicovaginal vesicovaginal fistulafistula

Paramesonephric ducts Paramesonephric ducts in Malein Male

Remains Remains rudimentaryrudimentary in male. in male.

Greater part disappears.Greater part disappears.

Cranial endCranial end of each duct persists as a small of each duct persists as a small rounded body attached to the testis called rounded body attached to the testis called Appendix of testisAppendix of testis..

It has been considered that the It has been considered that the prostatic urticleprostatic urticle represents the represents the utero-vaginal canalutero-vaginal canal and therefore and therefore homologous of the uterus, however, it is now homologous of the uterus, however, it is now believed to correspond mainly tobelieved to correspond mainly to vagina vagina ( and ( and possibly part of uterus).possibly part of uterus).

Development of external Development of external genitaliagenitalia

In 3In 3rdrd week of development, week of development, mesenchymal cellsmesenchymal cells from from primitive streakprimitive streak migrate around the migrate around the coacal membranecoacal membrane to form a pair of elevated to form a pair of elevated cloacal foldscloacal folds..

Cranial to the cloacal membrane the folds unite Cranial to the cloacal membrane the folds unite to form to form genital tuberclegenital tubercle..

Caudally, the folds are subdivided into Caudally, the folds are subdivided into urethral urethral foldsfolds anteriorly and anteriorly and anal foldsanal folds posteriorly. posteriorly.

Meantime, another pair of elevations the Meantime, another pair of elevations the genital genital swellingsswellings appear on each side of appear on each side of urethral urethral foldsfolds..

Development of Male external Development of Male external genitaliagenitalia

Genital tubercleGenital tubercle becomes cylindrical, which is now becomes cylindrical, which is now called the called the phallusphallus. Undergoes enlargement to form . Undergoes enlargement to form penispenis..

As the phallus grows, the As the phallus grows, the glansglans become visible by the become visible by the appearance of appearance of coronary sulcuscoronary sulcus..

PrepucePrepuce is formed from is formed from ectodermectoderm..

During this elongation, the phallus pulls the During this elongation, the phallus pulls the urethral urethral foldsfolds forward so that they form the lateral wall of the forward so that they form the lateral wall of the urethral grooveurethral groove..

This groove extends along the undersurface of the This groove extends along the undersurface of the elongated phallus but does not reach the most distal elongated phallus but does not reach the most distal part, part, glansglans..

The epithelial lining of the groove which originates The epithelial lining of the groove which originates in the in the endodermendoderm, forms the , forms the urethral plateurethral plate. .

At 3At 3rdrd month, the month, the two urethral foldstwo urethral folds close over the close over the urethral plateurethral plate, forming the , forming the penile urethrapenile urethra..

This canal This canal does notdoes not extend to the tip of the phallus. extend to the tip of the phallus.

Most distal end of the urethra is formed from the Most distal end of the urethra is formed from the ectodermal cellsectodermal cells from the tip of from the tip of glansglans, forming , forming external urethal meatusexternal urethal meatus..

The The genital swellingsgenital swellings fuse in the midline to form fuse in the midline to form scrotal sacscrotal sac into which the into which the testistestis later descend. later descend.


HypospadHypospadiasias

EpispadiaEpispadiass

PhimosisPhimosis

Development of Female external Development of Female external genitaliagenitalia

Genital tuberclesGenital tubercles : : clitorisclitoris..

Genital swellingsGenital swellings : : labia majoralabia majora

Urethral foldsUrethral folds : : labia minoralabia minora

Urogenital membraneUrogenital membrane breaks down and breaks down and establishes continuity between establishes continuity between urogenital sinusurogenital sinus and the and the exteriorexterior..


Clitoris may be absent, bifid or double.Clitoris may be absent, bifid or double.

Labia minora may show partial fusion.Labia minora may show partial fusion.

Urethra may open into anterior wall of Urethra may open into anterior wall of vagina, equivalent to vagina, equivalent to hypospadiashypospadias..

Priomordial Germ Cells & GonadsPriomordial Germ Cells & Gonads Priomordial germ cellsPriomordial germ cells are formed in the are formed in the epiblast epiblast during the 2during the 2ndnd week of week of

development, then move to wall of the development, then move to wall of the Yolk sacYolk sac..

During 4During 4thth week they move to developing week they move to developing gonadsgonads..

GonadsGonads do not develop as long as do not develop as long as primordial germ cellsprimordial germ cells do not reach them. do not reach them.

These cells have an These cells have an inducing effectinducing effect on the gonad. on the gonad.

Shortly before and during arrival of Shortly before and during arrival of primordial germ cellsprimordial germ cells, , the the epitheliumepithelium of the of the genital ridgegenital ridge proliferates, and proliferates, and epithelial cells penetrate the underlying epithelial cells penetrate the underlying mesenchymemesenchyme. .

Here they form a number of irregularly shaped cords, the Here they form a number of irregularly shaped cords, the primitive sex cordsprimitive sex cords. .

In both In both malemale and and femalefemale embryos, these cords are embryos, these cords are connected to surface epithelium, and it is impossible to connected to surface epithelium, and it is impossible to differentiate between the male and female gonad. Hence, differentiate between the male and female gonad. Hence, the gonad is known as the the gonad is known as the indifferent gonadindifferent gonad..

Development of testisDevelopment of testis Each Each testistestis develops from the develops from the coelomic coelomic

epitheliumepithelium..

If the embryo is genetically If the embryo is genetically malemale, the , the primordial primordial germ cellsgerm cells carry an carry an XYXY sex chromosome complex. sex chromosome complex.

The The primitive sex cordsprimitive sex cords continue to proliferate continue to proliferate and penetrate deep into the and penetrate deep into the medullamedulla to form the to form the testis or medullary cordstestis or medullary cords..

Toward the hilum of the gland, the cords break up Toward the hilum of the gland, the cords break up into a network of tiny cell strands that later give into a network of tiny cell strands that later give rise to tubules of the rise to tubules of the rete testisrete testis. .

A dense layer of A dense layer of fibrous connective tissuefibrous connective tissue, the , the tunica tunica albugineaalbuginea, separates the testis cords from the surface , separates the testis cords from the surface epithelium.epithelium.

In the 4In the 4thth month, month, testis cordstestis cords are now composed of are now composed of primitive germ cellsprimitive germ cells and and sustentacular cells of sustentacular cells of SertoliSertoli derived from the surface derived from the surface epitheliumepithelium of the of the gland.gland.

Interstitial cells of LeydigInterstitial cells of Leydig, derived from the original , derived from the original mesenchymemesenchyme of the gonadal ridge, lie between the of the gonadal ridge, lie between the testis cords. testis cords.

Testis cords remain solid until puberty, when they Testis cords remain solid until puberty, when they acquire a lumen, thus forming the acquire a lumen, thus forming the seminiferous seminiferous tubulestubules. .

Duct system of testesDuct system of testes We know most of the We know most of the mesonephric tubulesmesonephric tubules

degenerate.degenerate.

Some of these that lie near the Some of these that lie near the testistestis persist persist and, along with the and, along with the mesonephric ductmesonephric duct, , form the duct system of the testis.form the duct system of the testis.

The ends of The ends of seminiferous tubulesseminiferous tubules anastomose with one another to form the anastomose with one another to form the rete testesrete testes..

Rete testesRete testes, in turn, establishes contact , in turn, establishes contact with persisting with persisting mesonephric tubulesmesonephric tubules which form the which form the vasa efferentiavasa efferentia..

Cranial part of the Cranial part of the mesonephric ductmesonephric duct becomes becomes highly coiled on itself to form the highly coiled on itself to form the epididymisepididymis..

Its distal part forms the Its distal part forms the ductus deferensductus deferens..

Seminal vesicleSeminal vesicle arise on either side as a arise on either side as a diverticulum from the lower end of the diverticulum from the lower end of the mesonephric ductmesonephric duct..

The part of the mesonephric duct that lies The part of the mesonephric duct that lies between its opening into the between its opening into the prostatic urethtraprostatic urethtra and the origin of this diverticulum, forms the and the origin of this diverticulum, forms the ejaculatory ductejaculatory duct..

Ejaculatory duct


TestesTestes

- Absent on one or both sides.Absent on one or both sides.- DuplicatedDuplicated- Two testes may be fused togetherTwo testes may be fused together- Ectopia : Femoral canal, Perineum behind the Ectopia : Femoral canal, Perineum behind the

scrotum, Under the skin of lower part of abdomen.scrotum, Under the skin of lower part of abdomen.

Duct system of testisDuct system of testis

- Seminiferous tubules fail to connect with vasa Seminiferous tubules fail to connect with vasa efferentiaefferentia

- Ductus deferens may be absentDuctus deferens may be absent

Descent of TestesDescent of Testes

Testes develop in relation to Testes develop in relation to lumbar regionlumbar region of the of the posterior abdominal wall.posterior abdominal wall.

During fetal life they gradually descend to the During fetal life they gradually descend to the scrotumscrotum..

Reach Reach iliac fossailiac fossa during during 33rdrd month month..

Lie at the site of Lie at the site of deep inguinal ringdeep inguinal ring up to up to 77thth monthmonth..

Pass through the Pass through the inguinal canalinguinal canal during during 77thth month month..

Normally in the Normally in the scrotumscrotum by the end of by the end of 88thth month month..

Factors controlling the descent of Factors controlling the descent of testestestes

Not entirely clear.Not entirely clear.

Differential growth of body wall.Differential growth of body wall.

The gubernaculumThe gubernaculum

Processus vaginalisProcessus vaginalis

Hormones secreted by pars anterior of the Hormones secreted by pars anterior of the hypophysis cerebri.hypophysis cerebri.


Congenital Congenital indirect indirect inguinal inguinal herniashernias

CryptorchidisCryptorchidismm

HydroceleHydrocele

Development of ovaryDevelopment of ovary The The primitive sex cordsprimitive sex cords dissociates into small masses. dissociates into small masses.

The cells of each mass surrounds one The cells of each mass surrounds one primordial germ primordial germ cellcell or or oocyteoocyte, to form a , to form a primordial follicleprimordial follicle..

These sex cords then undergo These sex cords then undergo regressionregression and replaced and replaced by a new set of by a new set of cortical cordscortical cords arising from the arising from the coelomic epitheliumcoelomic epithelium..

Interstitial gland cellsInterstitial gland cells differentiates from differentiates from mesenchyme of the gonad.mesenchyme of the gonad.

As As no tunica albugineano tunica albuginea is formed, the germinal is formed, the germinal epithelium may contribute to the ovary even in the epithelium may contribute to the ovary even in the postnatal life.postnatal life.

Congenital anomaliesCongenital anomalies Absent on one or both sidesAbsent on one or both sides

DuplicatedDuplicated

May descend in to the inguinal canal or May descend in to the inguinal canal or even into labium majuseven into labium majus

Descent of ovaryDescent of ovary

Fate of Mesonephric duct Fate of Mesonephric duct (Wolffian duct) and tubules in the (Wolffian duct) and tubules in the

MaleMaleMesonephric ducts (Wolffian Mesonephric ducts (Wolffian ducts) gices rise to :ducts) gices rise to :

Ureteric buds from which the ureters, pelces, Ureteric buds from which the ureters, pelces, calyces and collecting tubules of the kidneys.calyces and collecting tubules of the kidneys.

Tigone of the bladderTigone of the bladder Posterior wall of the part of the prostatic Posterior wall of the part of the prostatic

urethra, cranial to the openings of the urethra, cranial to the openings of the ejaculatory ducts.ejaculatory ducts.

EpididymisEpididymis Ductus deferensDuctus deferens Seminal vesicalsSeminal vesicals Ejaculatory ductsEjaculatory ducts Mesodermal part of prostateMesodermal part of prostate Appendix of epididymisAppendix of epididymis

Remnants of mesonephric tubulesRemnants of mesonephric tubules

Vasa efferentiaVasa efferentia Superior aberrant ductulesSuperior aberrant ductules Inferior aberrant ductulesInferior aberrant ductules ParadidymisParadidymis

Fate of Mesonephric duct Fate of Mesonephric duct (Wolffian duct) and tubules in the (Wolffian duct) and tubules in the

FemaleFemaleVestigial structures like :Vestigial structures like :

EpoophoronEpoophoron

ParoophoronParoophoron

Control of differentiation of Control of differentiation of genital organsgenital organs

The factors that determine whether a male or The factors that determine whether a male or female genital system will develop are as follow:female genital system will develop are as follow:

Sex chromosomeSex chromosome i.e., XX for female and XY for male i.e., XX for female and XY for male

Y chromosome contains Y chromosome contains testis determining genetestis determining gene called the called the SRYSRY ( (sex determining region on Ysex determining region on Y) gene on ) gene on its short arm.its short arm.

SRY proteinSRY protein is the is the testis determining factortestis determining factor, under , under its influence its influence malemale development occurs. development occurs.

In its In its absenceabsence, , femalefemale development is established. development is established.

Health & Medicine

10.development of urogenital system