Development Of The Genital System Flashcards
Name the week:
Indifferent embryo
Sexual differentiation begins
Female and male genitalia can be recognized
Phenotypic differentiation complete
Weeks 1-6
Week 7
Week 12
Week 20
What is the indifferent gonad?
Where do they end up after gastrulation and body folding?
Where and when do they migrate after that?
Primordial germ cells specified within epiblasts
Yolk sac wall
Migrate up dorsal mesentery to enter genital ridge; week 5
When is the gonad indifferent?
What are the male and female somatic support cells?
Week 6
Male: Sertoli cells
Female: follicle cells
Both genital ducts form in the ____ of the urogenital ridge.
What are the two ducts and what do they become?
Which duct was a part of early kidney development?
Intermediate mesoderm
Mesonephric (Wolffian) ducts: epididymis, vas deferens, seminal vesicle, ejaculatory duct
Paramesonephric (Mullerian) ducts: oviduct, uterus, upper vagina
Mesonephric (Wolffian) ducts
Sexual dimorphism is dependent on the ____ chromosome and ____.
____ gene is on the sex-determining region of the Y chromosome
What does this gene determine?
Without this gene, continued development is ____ with ____ positively driving this development.
Y; autosomes
SRY
The gonad type and duct and genitalia development
Female; genes
What gene determines the formation of testis?
What chromosome is it on?
When is it active?
What cells express this gene?
SRY gene (also called TDF/testis determining factor)
Y chromosome
41-52 days
Somatic support cells (pre-Sertoli)
What is the job of the SRY gene?
____ surround primordial germ cells to organize/become seminiferous tubules.
Subset of intertubular cells differentiated into _____; recruited by ______.
Up-regulates testis-specific genes; drives formation of Sertoli cells from somatic cells
Sertoli cells
Fetal leydig cells; Sertoli cells
This gene is driven by SRY
Function of this gene
What remnants are left from the paramesonephric duct in males?
Sox9
Drives the production of Anti-Mullerian Hormone (AMH) from the Sertoli cells -> inhibits development of Mullerian (paramesonephric) ducts between weeks 8-10
Appendix testis, prostatic utricle
Leydig-derived testosterone drives the development of what?
This will form what in males?
When does the paramesonephric duct degenerate in males?
Mesonephric ducts
Epididymis, efferent ductules, vas deferens, seminal vesicles
Week 9
Sertoli cells generate ____ which cause regression of _____.
Sertoli cells also generate ____ which causes spermatogonia to become spermatozoa during ____.
AMH; paramesonephric ducts
Androgen binding factor; spermatogenesis
When do fetal leydig cells regress?
What do fetal leydig cells produce and what is the fx?
Fetal/early post natal life
Testosterone: causes mesonephric duct to become the ductus deferens, epididymis, seminal vesicle during weeks 8-12; driven by HCG of placenta
5 alpha reductase: causes testosterone to become dihydrotestosterone (DHT)
DHT drives the formation of what?
Adult leydig cells secrete ____.
What do they do?
Genital tubercle -> penis
Genital swellings -> scrotum
Urethral epithelium -> prostate
Androgens
Initiation of spermatogenesis, masculinization of brain, male sexual behavior
Development of the external genitalia begins with ____ external genitalia.
Rupture of cloacal membrane opens the phallic portion of urogenital sinus to exterior, forming an endodermally-lined plate called what?
What are remnants of the cloacal membrane at the ventral end of urogenital plate?
What is the ectodermally-covered mesodermal swelling at ventral and cranial end of phallic portion of urogenital plate?
Indifferent
Urogenital plate (endodermally lined)
Glans plate
Genital tubercle (mesoderm covered by ectoderm)
What is the urogenital plate?
When does it form?
___ drives lengthening and growth of genital tubercle and fusion of labioscrotal swellings to form sacrum.
____ continues to elongate creating a future urethra inside a tube of ____.
When is the urethral groove closed?
Remnant of phallic segment after cloacal membrane rupture
Early 7th week
DHT
Urogenital plate with ventral glans plate; urogental folds
Week 14
Gonads start around ____ and descend.
What shortens and becomes the anchoring ligament of the testis to the scrotum?
It is connected to the ____.
T10
Gubernaculum
Labia/scrotal swelling
The most common birth defect after cryptorchidism; urethral folds on either side of UG plate don’t fuse; urethra opens in inferior side of penis
Other birth defect associated with exstrophy of bladder; problem with anterior wall closure of the bladder
Hypospadias
Epispadias
Females don’t have ____, allowing ____ to initially suppress sox9 expression.
____ continually suppresses Sox9; maintaining female gonad (suppress Sertoli cell and Leydig cell differentiation).
Somatic cells differentiate into ____; primordial germ cells differentiate into _____.
Oogonia proliferate and differentiate into ____.
____ surrounds oocytes in inhibit further meiosis; oocytes stuck in meiosis I until ____.
SRY; Wnt4
FOXL2
Follicle cells; oogonia
Oocytes
Follicle cells; puberty
In females, no Sertoli cells therefore no ____; paramesonephric ducts are retained.
No leydig cells so _____ is lost.
Persistence of Müllerian (paramesonephric) ducts creates ____.
AMH
Mesonephric duct
Uterine tubes, uterus, vagina (upper portion)
When does the uterus form?
How does it formed?
What drives this formation?
____ are the unfused superior portion of the paramesonephric ducts.
What is a remnant of the mesonephric duct in females?
Weeks 9-10
Inferior paramesonephric ducts near the urogenital sinus fuse and form the uterus
Estrogen and progesterone from placenta
Uterine tubes
Gartner’s duct
What are uterus anomalies?
How do these form?
Double uterus; double vagina Double uterus Bicornate uterus Septated uterus Unicornate uterus Cervical atresia
Mainly formed because of lack of fusion of the paramesonephric ducts
Paramesonephric ducts fuse on the _____; this stimulates formation of the ____.
What is the upper vagina derived from?
Lower vagina?
The vagina is eventually ___.
What causes vaginal agenesis?
Urogential sinus; sinovaginal wall
Mesoderm; from paramesonephric duct system
Endoderm; from sinovaginal wall
Recanalize
Due to failure of normal vaginal plate development or failed canalizations
Phallic segment of the urogenital sinus forms what in the female?
Urethral portion of urogenital sinus becomes what?
Urogenital plate, glans plate, genital tubercle
Membranous urethra
No testosterone leads to no dihydrotestosterone and therefore no _____ and ______ in females.
No lengthening of genital tubercle and no fusion of urogenital folds or labioscrotal swellings
How does the broad ligament form?
Upon completion of uterus and oviduct formation, the remaining tissue thins and forms a _____ which supports ____.
Midline fusion of paramesonephric ducts; brings lower urogenital ridge within the pelvic cavity and is covered with peritoneum
Double fold of peritoneum (broad ligament and mesovarian); uterus and ovary
