Reproductive System Development Flashcards
Sex determination
- Chromosomal sex (XX vs. XY)
A. Sex-determining region (SRY) on Y chromosome encodes testis-determining factor (TDF)
B. TDF absent -> indifferent gonads -> ovaries
C. TDF present inhibits default signal => indifferent gonads -> testes - Gonads and hormones -> differentiation genital ducts and external genitalia
A. Androgen is hormones -> male tract and external genitalia from mesonephric duct- Anti-mullarian hormone (AMH) inhibits paramesonephric duct
- Estrogen -> female tract and genitalia (paramesonephric)
A. DHT absent -> mesonephric degrades
Indifferent stage of gonad dev
- Primordial in thoracic region
- Intermediate mesoderm
- Coelomic mesothelium thickens
- Primordial germ cells (PGCs) invade
A. From epiblast-> thru primitive streak -> yolk sac (wk 3)
B. Migrate along dorsal mesentery (wk 4) -> primitive gonads (wk 5)
C. Invade genital ridge (wk 6)- If doesn’t happen, no gonads
- Primitive sex cords form from thickened coelomic mesothelium
- Cranial suspensory lig and gubernaculum form
Indifferent stage of urogenital duct dev
- Mesonephric (wolffian) ducted dev
- Paramesonephric (Mullerian) duct forms on sides wolffian duct
A. Cranial end stays open to coelomic (peritoneal) cavity
B. 2 Müllerian ducts sacral/pelvic region merge -> uterovaginal primordium
C. Uterovaginal primordium fuses post wall urogenital sinus (pelvic) but doesn’t open into it
D. Sinus tubercle forms -> hymen (female) or seminal colliculus (male)
Testes dev
- Testes dev from primordial gonads if TDF present
A. Medullary (testis) cords from gonadal cords -> tubules for spermatogenesis- Spermatogonia (diff PGC)
- Sustentacular (sertoli) from coelomic mesothelium: structures support cells
- Spermatogenesis after puberty
- Dev lumen at puberty and join rete testes
B. Interstitial feels (of Leydig) from intermediate mesoderm - Hormone producing
- Wk 8 -> testosterone
C. Tunica albuginea: thick, fibrous capsule under tunica vaginalis w/ septa into medulla of testes - Separates testis cords from surface epithelium
Male UG tracts and accessory gland dev
- In response to AMH secreted by sustentacular cells in testes
A. Müllerian ducts regress and degenerate
B. Vestiges may remain- Prostatic utricle: caudal end
- Appendix testes: cranial end
- In response to testosterone and DHT secreted by interstitial cells
A. Mesonephric tubules near developing testes persist and connect rete testes -> efferent ductules- Paragenital tubules dev at caudal pole but don’t connect rete testis
A. Vestige = paradidymis
B. Mesonephric ducts persist -> genital tract and accessory glands
C. Epithelium outgrowths prostatic urethra -> glandular part prostate gland
D. Epithelium outgrowths spongy urethra -> bulbourethral glands
- Paragenital tubules dev at caudal pole but don’t connect rete testis
Descent of testes
- Pass ant ureters -> inguinal canal
- Gubernaculum persists -> scrotal (testicular) lig
- Cranial suspensory lig. Regresses
Ovary dev
- Dev in absence of TDF
A. Rudimentary medullary cords form -> degrade -> replaced by vascular storms (intermediate mesoderm)
B. Coelomic mesothelium -> cortical cords -> primordial follicles- Surround PGCs and oogonia
- Oogonia arrested Prophase I -> primary oocyte
- Oogonia and primary oocyte number dec from atresia
- Birth: 1 million primordial follicles remain
C. Tunica albuginea-> fibrous capsule under ovarian surface epithelium
Female urogenital tracts and accessory glands dev
- In absence androgenic hormones
A. Mesonephric duct degenerates
B. Vestiges may remain- Epoophoron: cranial
- Paraoophoron: caudal
A. Can form Gartner cyst is uterus/vagina (benign)
- In absence AMH and facilitated by estrogen
A. Paramesonephric ducts persist -> genital tract- Uterine tubes from sup, unfused portions
- Uterovaginal canal from fusion at midline -> uterus, cervix, and vagina
- Broad lig from mesentery being dragged around
B. Vaginal plate from sinus tubercle -> inf vagina and hymen - Dev separate external openings
C. Epithelial outgrowths urethra -> urethral and paraurethral glands
D. Epithelial outgrowths UG sinus -> greater vestibular glands
Descent of ovaries
- Gubernaculum guides ovaries down -> lateral uterus
A. Sup -> ovarian lig
B. Inf -> round lig of uterus - Cranial suspensory lig -> suspensory lig of ovary
A. Ovarian a. And v. Travel w/ it
Indifferent stage dev external genitalia
- Mesenchyme surrounding cloacal membrane proliferates and differentiates -> 3 structures
A. Genital tubercle -> primordial phallus (penis/clitoris)
B. Urethral folds dev on sides of cloacal membrane
C. Genital (labioscrotal) swelling dev lateral to UG folds - Posterior UG fold and genital swelling fuse at midline
A. Cloacal membrane divides -> UG and anal membrane- Urorectal septum
- UG membrane degenerates -> UG sinus open to external environment
A. Urethral groove = cleft between urethral folds
B. Floor urethral groove from phallic part UG sinus
Male external genitalia dev
In response to DHT
1. Primordial phallus elongates externally and internally ->
A. Root of penis (internal)
1. Crura of penis : continuous w/ corpora cavernosa
2. Bulb of penis : continuous w/ corpora spongiosum
B. Body of penis (external)
1. Corpora cavernosa : continuous w/ crura of penis
2. Corpus spongiosum: continuous w/ bulb of penis
C. Glans of penis: distal expansion of corpus spongiosum
2. Urethral folds and groove elongate w/ phallus
A. Urethral groove -> spongy urethra
B. Urethral folds -> ventral skin of shaft and penile raphe
3. Labioscrotal swelling expand and medial surface fuses -> single scrotum
A. Scrotal raphe externally
B. Scrotal septum internally and sep testes
4. Ectodermal cords penetrate tissue of glans
A. Prepuce from one ectodermal cord
B. Navicular fossa of urethra from another ectodermal cord and connects w/ spongy urethra
Female external genitalia dev
- Primordial phallus elongates internally and bends forward/inf externally w/ elongation ->
A. Glans of clitoris
B. Corpora cavernosa of clitoris
C. Bulbs of vestibule - Urethral folds expand laterally -> labia minor
- Urethral groove -> vestibule of vagina
- Labioscrotal swelling -> labia majora and mons pubis
A. Ant and post commisures
Mesonephric duct derivatives
Males
- Appendix of epididymis
- Duct of epididymis
- Ductus deferens
- Seminal glands
- Ejaculatory duct
- Trigone of urinary bladder
Females
- Addendum vesiculosa
- Duct of epoophoron
- Gartner duct
- Trigone of bladder
Mesonephric tubule derivatives
Males
- Efferent ductules of testis
- Paradidymis
Females
- Epoophoron
- Paroophoron
Ureteric bud derivatives
Collecting systems both sexes
- Ureter
- Renal pelvis
- Calices
- Collecting ducts
- Connecting tubules