Development of Genital System Flashcards
What embryological layer do the nephrogenic cord and urogenital ridge arise from?
Intermediate Mesoderm
What gives rise to the primary sex cords?
Coelomic epithelium
What primordial germ cells does the coelomic epithelium give rise to?
Sertoli cells, seminiferous cords
Follicle cells
What primordial germ cells does the intermediate mesoderm give rise to?
Interstitial/Leydig cells, Tunica Albuginea
Thecal cells
What week does sexual differentiation begin?
Week 7
What week can female and male genitalia be recognized?
Week 12
In what week is phenotypic differentiation of the genitalia complete?
Week 20
What does the paramesonephric duct give rise to?
Female internal genitalia:
Oviduct
Uterine tubes
Uterovaginal primordium (Uterus and Upper Vagina)
What does the mesonephric duct give rise to?
Male internal genitalia:
Epididymis
Vas Deferens
Seminal vesicle
Ejaculatory duct
What is the mesonephric duct also known as?
Wolffian Duct
What is the paramesonephric duct also known as?
Mullerian duct
What does the intermediate mesoderm of the urogenital ridge give rise to?
Mesonephric and paramesonephric ducts
What is the sex-determining region of the Y chromosome?
SRY gene
What does the SRY gene induce Leydig cells to do?
Produce testosterone => Persistent mesonephric ducts => DHT => +Male external Genitalia
What does the SRY gene induce Sertoli cells to do?
Produce AMH => degenerate paramesonephric ducts => - female external genitalia
In what week does gametogenesis occur?
Week 2
What do the primary sex cords give rise to?
Medulla of gonads
What cells does the Allantois/Yolk sac endoderm contain? In what weeks?
Primordial germ cells from epiblast
Weeks 3 and 4
In week 5, what are the primordial germ cells doing?
Migrating through dorsal mesentery
In week 6, what are the primordial germ cells doing?
Colonizing primary sex cords
Oogenesis is the increase in oogonia by what type of cell division?
Mitosis
In what prenatal month is the number of oogonia the largest?
5th prenatal month
At what cell division stage is the oocyte arrested at ovulation?
Meiosis I
At what cell division stage is the oocyte arrested at fertilization?
Meiosis II
What is the central event of sex determination?
Genetic differentiation (XX and XY)
Differentiation of Testes
What are the secondary events of sex determination?
Production of humoral factors by gonads (release of testosterone, estrogen) to produce phenotypic differentiation
What is the activator of the SRY gene?
Testis-determining Factor (TDF)
Pt with Ovotesticular DSD will present with what?
True gonadal intersex - both testicular and ovarian tissue, ovotestis
Male or female phenotype with ambiguous external genitalia
What DSD can be caused by exposure of a female fetus to excessive androgens?
46, XX DSD
How will 46XX DSD present?
Normal female internal genitalia
Masculinized external genitalia - clitoral hypertrophy, partial fusion of labia majora, persistent urogenital sinus
Congenital Adrenal Hyperplasia is a deficiency in what enzyme? What does it cause?
Deficient 21-Hydroxylase
Causes reduction in cortisol and excess production of androgens => Masculinized external genitalia
Congenital Adrenal Hyperplasia is an example of what kind of DSD?
46,XX DSD
An inadequate production of testosterone or AMH can result in what kind of DSD?
46XY DSD
How may a pt with 46XY DSD present?
Rudimentary to normal testicular development
Persistent paramesonephric ducts
Female/Ambiguous external genitalia
What kind of syndrome would a patient have if they present with a blind end vagina, absent uterus, and no menstruation?
Androgen Insensitivity Syndrome
What is the genotype and phenotype of a patient with Androgen Insensitivity Syndrome?
46 XY, present testes
Normal external female genitalia, breast development, and female characteristics
No menstruation, uterus/uterine tubes
A 5a-reductase deficiency would result in what?
(Inability to convert testosterone to DHT)
Normal internal male genitalia
Ambiguous External genitalia
In what week does the gonadal ridge appear on the medial side of the mesonephros?
Week 5
What do the secondary sex cords give rise to?
Cortex of gonads:
Primordial follicles
Granulosa cells
What do the mesonephric tubules give rise to?
Rete testes
Efferent ductules
What is the prostatic utricle an embryological remnant of?
Paramesonephric duct (NOT MESONEPHRIC)
Appendix testis is an embryological remnant of what?
Paramesonephric duct (Not mesonephric)
Appendix epididymis is an embryological remnant of what?
Mesonephric duct (not paramesonephric)
How is the sinus tubercle formed?
Projection of paramesonephric ducts to the urogenital sinus (bladder)
Embryological remnants of the mesonephric duct in females?
Epophoron (closer to ovary)
Paroophoron (closer to uterus)
Gartner’s cyst (lateral wall of vagina)
What layer are the sinovaginal bulbs derived from?
Endoderm
What failed in Uterus Didelphys?
Paramesonephric ducts did not fuse, formation of L and R uterus
What failed in Uterus Arcuatus?
Milder form of incomplete paramesonephric duct fusion
What failed in Uterus Bicornis?
Incomplete Paramesonephric duct fusion
What failed in Uterus Bicornis Unicoilis?
Atrophy of paramesonephric duct => no fusion
What failed in Cervical Atresia?
Caudal paramesonephric duct atrophy => Blind end vagina, unable to shed uterine lining => abdominal pain
What failed in vaginal atresia?
Failure of sinovaginal bulbs and vaginal plate to form => no vaginal canal
What is the embryological origin of the bladder and the urethra?
Hindgut endoderm
In males, what does the pelvic part of the urogenital sinus give rise to?
Prostate
What does the phallic part of the urogenital sinus give rise to?
Bulbourethral glands
What layer gives rise to the smooth muscle and connective tissue of the prostate and bulbourethral glands?
Splanchnic mesoderm
What influences male external genitalia to form?
Dihydrotestosterone (DHT)
What does the genital tubercle give rise to?
Glans penis
Glans clitoris
What do the urethral (urogenital) folds give rise to?
M: Lateral walls of urethra, spongy urethra, penile raphe
F: Frenulum of labia minora
What do the labioscrotal swellings give rise to?
Scrotum
Labium majus, mons pubis
What failed in glandular hypospadia?
Incomplete fusion of the urogenital folds/dysfunctional development of navicular fossa
Ventral
What failed in penile hypospadia?
Incomplete fusion of urogenital folds on the shaft of the penis
ventral side
What failed in periscrotal hypospadia?
Lack of fusion of the labioscrotal swellings
What failed in epispadias?
Improper location of genital tubercles to cloacal membrane
Dorsal
Associated with bladder exstrophy (protrusion through abdominal wall)
What embryological layer does the suspensory ligament arise from?
Mesoderm
What does the ovarian ligament arise from?
Cranial part of gubernaculum
What does the caudal part of the gubernaculum give rise to?
Round Ligment of the uterus
Homologs of mesonephric tubules
M: Efferent ductules
F: Epoophoron, paroophoron
Homologs of mesonephric duct
M: Ductus deferens, seminal vesicle, ejaculatory duct
F: Duct of epoophoron, duct of paroophoron, Gartner’s cyst
Homologs of Paramesonephric duct
M: Prostatic utricle
F: Uterine tube, uterus, superior 1/3 of vagina
Homologs of urogenital sinus
M: Bladder, urethra, prostate, bulbourethral gland
F: Bladder, urethra, inferior 2/3 of vagina, greater and lesser vestibular glands, vagina, vestibule, hymen
Homologs of genital swellings
M: Scrotum
F: Labia Majora
Homologs of urethral folds
M: Floor of spongy urethra
F: Labia Minora
Homologs of gubernaculum
M: Gubernaculum testis
F: Ovarian L., Round L. of the Uterus
