Severson's normal genital development; 4.7 Flashcards
What forms the urogenital ridge?
Intermediate mesoderm
When does a fetus start developing specific genitalia?
7th week of development
What gene is necessary for male development?
SRY gene (Sex-determining Region of Y)
What is the SRY gene responsible for?
SRY gene → testis-determining factor → gonadal cords differentiate into seminiferous tubules
What is produced in fetal testes that determines maleness?
Testosterone
What is necessary for complete ovarian development?
XX genotype (and not having Y)
Is femaleness determined by hormonal influence?
No…but estrogen (produced by placenta and ovaries) → feminization of external genitalia
What are the contents of the gonads?
Mesothelium (coelomic epithelium)
Mesenchyme (underlying the mesothelium)
Primordial germ cells
Where do the primordial germ cells originate?
Primordial cells originate in the yolk sac
Where do the primordial germ cells migrate? When?
Along the dorsal mesentery of the hind gut to the gonadal ridges
Latter half of the 5th week
Where do the primordial germ cells go in males?
Migrate into the gonadal cords
Where do the primordial germ cells go in females?
Remain in underlying mesenchyme
What do the gonadal cords (w/ primordial germ cells) become?
Seminiferous tubules
Sertoli cells
Rete testis
Despite not maturing during the fetal period, Sertoli cells still contribute to development. What do they produce? What causes the secretion?
Sertoli cells produce anti-Mullerian hormone d/t hCG
What does anti-Mullerian hormone do?
Suppresses development of the paramesonephric (Mullerian) ducts
What do mesonephric tubules become?
Efferent ductules
What do efferent ductules do?
Efferent ductules connect to the mesonephric duct…which becomes the epididymis
What does the mesenchyme in the gonads become?
Cells of Leydig → synthesize androgenic hormones
What happens with primordial germ cells in ovaries?
Undergo mitosis → numerous oogonia
What causes oogonia to enter prophase I of meiosis?
Meiosis-stimulating factor
What are oogonia called after entering prophase I of meiosis?
Primary oocytes
What is needed for oogonia/oocytes to be considered primordial follicles?
Follicular cell association
How long do primordial follicles stay in prophase I?
Until a few days before ovulation
After ovulation, what phase of meiosis do secondary oocytes arrest in?
Metaphase II
How long do secondary oocytes remain in metaphase II?
Until fertilization
What are paramesonephric (Mullerian) ducts?
Coelomic epithelium along the mesonephric ridge…lateral to the mesonephric (Wolffian) ducts
What happens to the caudal ends of the Mullerian ducts?
Fuse and terminate on the urogenital sinus b/w the ends of the mesonephric ducts → uterovaginal primordium → sinus (Mullerian) tubercle
What happens to the cranial ends of the Mullerian ducts?
Open into the coelomic cavity
As said earlier, Sertoli cells produce anti-Mullerian hormone which causes the Mullerian ducts to degenerate. What remains of the Mullerian ducts in males?
Prostatic utricle
Appendix of of testis
As said earlier, Leydig cells produce testosterone. What is the result of testosterone action on mesonephric (Wolffian) ducts?
Wolffian ducts become the epididymis, ductus deferens, and ejaculatory duct
As said earlier, Leydig cells produce testosterone. What is the result of testosterone action on the ductus deferens?
Seminal vesicles develop
As said earlier, Leydig cells produce testosterone. What is the result of testosterone action on the urethra?
Formation of prostate and bulborurethral glands
What does the processus vaginalis become in males?
Tunica vaginalis
What does the gubernaculum become in females?
Ligament of the ovary and the round ligament of the uterus
What does the genital tubercle at the cranial end of the cloacal membrane become?
Genital tubercle → phallus
What does the phallus become?
Phallus + testosterone → penis
Phallus - testosterone → clitoris
The corpora cavernosa and corpus spongiosum of the penis are derived from what?
Mesenchyme of the phallus → corpora cavernosa and corpus spongiosum
What does fusion of urogenital folds form in males?
Spongy urethra is the inner cavity
Penile raphe is the line of fusion on the ventral surface
How does the rest of the urethra form (obviously just in males)?
The ectodermal cord grows in from the glans and connects to the spongy urethra
What happens to the urogenital folds in females?
Become the labia minora…do NOT fuse
What is the name of the space between the urogenital folds?
Vestibule
