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Development of the Reproductive System Crissman Anatomy Block II Unit II


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What starts earlier, urinary or genital system development?
Urinary system starts earlier.
What does the genital system form from?
The medial aspect of the urogenital ridge.
When is chromosomal or genetic sex determined?
At fertilization.
When is phenotypic sex of an embryo manifested?
7th week of gestation.
What is the indifferent stage of sexual development?
When gametes migrating from the yolk sa into the developing gonadal primordial in the urogenital ridge.
Where is the gonadal primordia located?
Medial to the developing mesonephric kidney.
What is the only thing indicative of future sex in the indifferent stage?
A barr body (inactive X chromosome)
What does phenotypic differentiation of gender begin with?
Gonadal differentiation.
What do differentiating gonads do/influence the formation of? (3)
Influence the formation of the appropriate duct system.
Differentiation of external genitalia.
Secondary sex characteristics
What are secondary sex characteristics? Give examples.
Body configuration, breasts, hair pattern, body fat pattern
What can overcome the genetic sex of an individual so that genetic sex does not match phenotypic sex?
Environmental factors.
What does the male require to form testis?
Testis-Determining Factor (TDF)
What does testis-determining factor do?
Directs the formation of the complete phenotype.
What is the baseline or default condition or sex of an embryo?
What is the origin of germ cells?
What are the 3 sources from which indifferent gonads are derived?
Mesothelium, mesenchyme, primordial germ cells.
What is the mesothelium? What is another name for it?
Lining of the posterior abdominal wall (coelomic epithelium)
Where is the mesenchyme located?
Subjacent to the mesothelium
Where are primordial germ cells from?
Endodermal lining of yolk sac.
What is the indifferent gonad period?
When the developing gonad cannot be identified as male or female.
What are the 5 steps of indifferent gonadal formation?
1) Proliferation of the mesothelium on the medial aspect of the forming urogenital ridge
2) Primordial germ cells migrate into urogenital ridge
3) Coelomic epithelium (mesothelium) proliferates and grows into the mesenchyme.
4)Primordial germ cells enter mesenchyme and are incorporated into the gonadal cords
5) Primordial germ cells enter the gonad and undergo proliferation.
What forms the urogenital ridge?
Thickening of mesothelium and proliferation of underlying mesenchyme.
Where does the mesothelium for the genital system develop relative to the mesonephros?
Medial to the forming mesonephros.
Where are primordial germ cells initially found?
Endoderm of yolk sac.
What controls primordial germ cells? (gene)
BMP-4 gene expression
What do the primordial germ cells migrate along in order to reach the gonadal ridges?
Dorsal mesentery.
If the primordial germ cells are misdirected what results?
What forms gonadal cords?
Coelomic epithelium that grows into mesenchyme.
What is another name for the gonadal cords?
Primitive or primary sex cords.
What induces the proliferation of primordial germ cells once they enter the gonad?
LIF and STEEL factor.
List the factors expressed during indifferent gonad formation. (6)
STEEL factor
What does Wt-1 do?
Affects somatic cells, not germ cells.
What does SF-1 do?
Steriodogenic factor affects somatic cells not germ cells.
What does Lim-1 do?
Absence prevents formation of anterior head as well as kidneys and gonads.
What does Oct-4 do?
Transcription factor responsible for maintaining the totopotential state of the germ cells.
What gene produces testis detrmining factor? What does this do?
Sry Gene, this causes the indifferent gonad to differentiate into the testis.
Where is the Sry gene located?
short arm of Y chromosome.
What happens if TDF is absent?
Indifferent gonad develops into an ovary.
What gene does TDF inhibit?
What is the relationship between the Dax-1 and Sry genes?
BOth are activated at the same time.
What does Dax-1 do?
Inhibits testis formation.
What does Sox-9 do?
Causes the gonadal cords to form from thickened coelomic mesotherlium and grow into the underlying mesencyme of the medullary region.
What separates the gonadal cors from the coelomic epithelium?
Forming tunica albuginea.
What do the outer portion of gonadal cords differentiate into?
Seminiferous Tubules.
What forms the sertoli cells?
A solid cord of cells in the outer poriton of gonadal cords.
Where is the inner portion of the gonadal cords located and what forms from it?
THey are located against the mesonephric tubules. They form a meshwork that differentiates into the Rete Testis.
What do the mesonephric tubules against the meshwork of the inner portion of the gonadal cords form?
Efferent ductules.
What forms the intersitial cells of leydig?
Mesenchyme that lodges between the seminiferous tubules.
What do Fetal leydig cells secrete?
Testosterone and androstenedione.
What do testosterone and androstenedione do?
Induce differentiation of the genital ducts.
How do testosterone and androstenedione reach peak levels?
Via stimulation by human chorionic gonadotropin.
Do fetal leydig cells persist?
NO! They do not appear agian until after puberty when they stimulate spermatogenesis.
What forms the seminiferous tubules?
Gonadal cords.
What do gonadal cords consist of?
Primarily sertoli cells with scattered spermatogonia.
What do Fetal sertoli cells produce?
Mullerian-Inhibiting Substance (MIS)
And Meiosis-Inhibiting Factor.
What does Mullerian-Inhibiting substance do? What secretes it?
It causes involution of the femal ducts. Fetal sertoli cells secrete it.
What does meiosis inhibiting factor do? What secretes it?
It slows proliferation of primordial germ cells, creating an environment within the testis that does not encourage meiosis and spermatogenesis. It is secreted by fetal sertoli cells.
What happens if sertoli cells do not recieve a Sox-9 signal at the appropriate time?
Germinal cells will begin to undergo meiosis and form an ovary.
Which is identifiable earlier a testis or an ovary?
A testis.
What supresses formation of testicular structures?
Expression of Dax-1
What happens if primordial germ cells migrate in the formation of an ovary?
The indifferent gonad regresses and forms streak ovaries.
What do gonadal cords develop from in females?
Coelomic mesothelium.
What do gonadal cords form in the central medullary region in ovaries?
Rete ovarii.
What do rete ovarii contain? What are they in contact with?
They are in contact with mesonephric tubules and contain germ cells.
What do cortical cords form from in females?
Coelomic mesothelium.
Where do most of the germinal cells become embedded in?
In cortical cords.
Where do oogonia undergo mitosis?
In cortical cords or cortex
Where do primordial follicles form in females?
In the outer cord.
What induces oogonia to tenter meiosis?
Meiosis stimulating factor.
What stage are oocytes arrested in?
Diplotene stage of prophase of Meiosis I.
Where does meiosis stimulating factor in females arise from?
Mesonephric tubule cells associated with the rete ovarii.
Where do most primordial follicles form?
In the cortical area of the ovary.
Where does tunica Albuginea form?
At the corticomedullary junction of the fetal ovary.
What do primordial follicles consist of?
Oocyte and follicular cells.
What are oocytes derived from?
Priomordial germ cells arising from the endoderm of the yolk sac.
What do follicular cells arise from?
Coritical cords arising from coelomic mesothelium and mesenchyme from mesonephric tubules.
Where do stroma cells in ovaries arise from?
What differentiates testis and ovaries at 7 weeks?
Testis has gonadal cords
What differentiates testis and ovaries at 2 weeks postnatally?
Ovaries have primordial follicles.
What differentiates testis and ovaries at 21 weeks?
Testis have primarily sertoli cells and scattered dark spermatogonia.
WHat does indifferent gonad diifferentiate into?
Testis or ovary.
What do the gonadal cords of the testes form?
Seminiferous tubules containing sertoli cells and spermatagonia (from primordial germ cells) and Rete testis arise from the meshwork.
What do mesonephric tubules of the testis form?
Efferent ductules.
What do gonadal cords of the ovaries form?
Nothing they degerate.
What do the cortical cords of the ovaries form?
Primordial follicles containing oogonia from the primordial germ cells.
When is the mesonephric duct (Wolffian) formed?
With the mesonephric kidney.
What initially forms the paramesonephric ducts (mullerian)?
Longitudinal invagination of coelomic mesothelium on the surface of the urogenital ridge lateral to the mesonephric duct.
What forms the genital ducts of the gonad for females?
The paramesonephric duct or mullerian duct.
Describe the development of the paramesonephric ducts.
Longitudinal invagination of coelomic mesothelium on the surface of the urogenital ridge lateral to the mesonephric duct becomes a solid cord of cells. This grows caudally to reach the UG sinus between the entrace of mesonephric ducts. It then develops a lumen cranial to caudal. The funnel shaped cranial end opens into the ceolomic cavity. THe caudal end does NOT open into the UG sinus.
What induces paramesonpehric ducts to degenerate in males? What secretes this?
Mullerian-Inhibiting substance secreted by sertoli cells induces paramesonephric ducts to degenerate.
What secretes testosterone?
Interstitial cells of leydig.
What does testosterone from leydig cells do for the male duct system?
Induces distal mesonephric duct to become convoluted and to form the epididymis, ductus deferens, ejaculatory ducts and seminal vesicles.
What do Hoxa-10 and 11 form in the male duct system?
What do Hoxd-11,12,13 form?
The ductus deferens.
What are the 2 remnants of the paramesonephric duct in males?
Prostatic utricle (homologue to vagina)
Appendix to testis (superior pole of testis)
What parts of the male duct system and accessory sex glands are developed from the urogenital sinus? (7)
Bladder, Membranous and prostatic urethra, penile urethra, prostate gland, bulbourethral glands and glands of Littre.
What part of the urogenital sinus does the bladder develop from?
Vesical portion.
What part of the urogenital sinus does the membranous and prostatic urethra develop from?
Pelvic portion
What part of the urogenital sinus does the Penile urethra develop from?
Phallic portion
What part of the urogenital sinus does the prostate gland develop from?
An outgrowth of the endoderm.
What part of the urogenital sinus does the bulbourethral and Glands of Littre develop from?
Endodermal derived penile urethra
Describe how the prostate gland forms.
In response to signalling from the testosterone induced mesenchyme just below the bladder endoderm begins to bud here.
What gene determines where the prostate gland will develop?
When will the female duct system develop?
If ovaries are present or gonads absent.
What happens if there is an absence of testosterone in duct formation?
Mesonephric ducts will regress
What happens if there is an absence of mullerian Inhibiting substance in duct formation?
Paramesonephrogenic duct develops into female duct system.
What is Wnt-4 gene needed for?
Paramesonephric duct development
What is necessary for Hoxd 10-13 genes to be expressed?
What does Wnt-7a do?
It is necessary for Hoxd 10-13 genes to be expressed.
What does the cranial portion of the paramesonephric duct form in females?
Uterine tubes.
What happens to the cranial opening of the paramesonephric ducts in females?
They become the fimbriated end of the infundibulum.
Describe the motion of the caudal ends of the paramesonephric ducts in relation to the mesonephric duct.
They move medially and ventrally.
What do two mullerian ducts form in the midline by fusing?
Uterovaginal primordian.
What does the uterovaginal primordium bulge into the urogenital sinus as?
The sinus tubercle
Does the female duct system open into the urogenital sinus?
What does the midline portion of the uterovaginal primordium form?
Uterus and part of the superior portion of the vagina.
As the mullerian ducts migrate toward the midline what do they carry with them? What does this form?
THey carry broad ligament with them which forms rectouterine and vesicouterine pouches.
Describe the formation of the uterus.
The superior poriton of the paramesonephric ducts in the primordium fuse together. The wall between the lumens degenerates to form the lumen of the uterus.
Describe the formation of the vagina.
Inferior poriton of mullerian duct forms the superior portion of the vagina.
What is the sinus tubercle?
A bulge where the fused mullerian ducts join the urogenital sinus.
Does the sinus tubercle open into the urogenital sinus?
WHat does the sinus tubercle do?
Stiumulates proliferation of endoderm of urogenital sinus.
What does the sinus tubercle form?
2 sinovaginal bulbs
What do the sinovaginal bulbs form?
Sinovaginal plate by fusing together.
How does the lumen of the vagina develop?
Cells in the center of the sinovaginal plate degenerate.
What direction does canalization of the vagina go?
Posterior to anterior.
What is the epithelium of the vagina from?
Endoderm of urogenital sinus or possibly supperior portion from mullerian duct and inferior poriton from endoderm of UG sinus.
What is the hymen?
A membrane that separates the urogenital sinus from the lumen of the vagina at the inferior end of the urogenital sinus in fetal life.
What does the hymen separate in a newborn?
The vaginal opening from the vestibule.
Does the hymen persist usually after birth?
NO it usually ruptures after birth.
What do the greater vestibular glands (of Bartholin) form from?
Outpocketings of the urogenital sinus endoderm.
What is double uterus and double vagina? What is it caused by?
Characterized by 2 uteri and vaginas side by side. It is caused by incomplete fusion of mullerian ducts and incomplete recanalization of the sinovaginal plate.
What is double uterus? What causes it?
Two uteri, one vagina
It is caused by incomplete fusion of the mullerian ducts into uterovaginal primordium.
What is bicornuate uterus? WHat is it caused by?
Two uteri, one vagina, small oviduct. It is caused by partial fusion of Mullerian ducts or retarded growth of one mullerian duct so it does not fuse with the other in the midline
WHat is septate uterus? What is it caused by?
It is characterized by septum dividing lumen of uterus in two. It is caused by the wall between the fused mullerian ducts in the uterovaginal primordium failing to degenerate.
What is a unicornuate uterus? What is it caused by?
It is characterized by a partial uterus, single oviduct and vagina. It is caused by development of a single Mullerian duct.
What are the remnants of the paramesonephric ducts in females?
Hydatid(of Morgagni)
What is the hydatid (of Morgagni)? Where is it located?
It is a vesicular structure adjacent to the infundibulum.
What are the remnants of the mesonephric ducts in females?
Appendix Vesiculosa
Ducts of Cysts of Gartner
What is the appendix vesiculosa a remnant of in females?
Mesonephric tubules.
What is the epoophron a remnant of in females?
Mesonephric tubules forming the efferent ductules and epididymis.
What is the paraoophoron a remnant of in females?
From mesonephric tubules forming efferent ductules and epididymis like the epoophron but it is closer to the uterus.
Where are the duct of cysts of Gartner found?
Lateral to the uterus and vagina.
Is there Mullerian inhibiting substance in females? What happen as a result of this?
NO MIS so Dax-1 is not inhibited from suppressing testis.
What happens to the mesonephric ducts in females?
They regress.
What does the superior part of the paramesonephric duct form?
What does the inferior part of the paramesonephric duct form?
Fuses to form uterovaginal primordium.
What does the superior part of the uterovaginal primordium form?
Uterus and induces formation of the uterovaginal plate.
What does the uterovaginal plate form?
Vagina from endoderm of the UG sinus.
How long does the indifferent stage of formation for external genitalia last?
7 weeks.
When do sexual characteristics of external genitalia begin to appear?
9th week
When is genitalia differentiation completed by?
12th week.
When is external genitalia differentiation completed by?
12th week.

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