Reproductive System Development

Question 1

Sex determination

Answer 1

1. 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
2. Gonads and hormones -> differentiation genital ducts and external genitalia
   A. Androgen is hormones -> male tract and external genitalia from mesonephric duct
   
   1. Anti-mullarian hormone (AMH) inhibits paramesonephric duct
   2. Estrogen -> female tract and genitalia (paramesonephric)
      A. DHT absent -> mesonephric degrades

Question 2

Indifferent stage of gonad dev

Answer 2

1. Primordial in thoracic region
2. Intermediate mesoderm
3. Coelomic mesothelium thickens
4. 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)
   
   1. If doesn’t happen, no gonads
5. Primitive sex cords form from thickened coelomic mesothelium
6. Cranial suspensory lig and gubernaculum form

Question 3

Indifferent stage of urogenital duct dev

Answer 3

1. Mesonephric (wolffian) ducted dev
2. 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)

Question 4

Testes dev

Answer 4

1. Testes dev from primordial gonads if TDF present
   A. Medullary (testis) cords from gonadal cords -> tubules for spermatogenesis
   
   1. Spermatogonia (diff PGC)
   2. Sustentacular (sertoli) from coelomic mesothelium: structures support cells
   3. Spermatogenesis after puberty
   4. Dev lumen at puberty and join rete testes
      B. Interstitial feels (of Leydig) from intermediate mesoderm
   5. Hormone producing
   6. Wk 8 -> testosterone
      C. Tunica albuginea: thick, fibrous capsule under tunica vaginalis w/ septa into medulla of testes
   7. Separates testis cords from surface epithelium

Question 5

Male UG tracts and accessory gland dev

Answer 5

1. In response to AMH secreted by sustentacular cells in testes
   A. Müllerian ducts regress and degenerate
   B. Vestiges may remain
   
   1. Prostatic utricle: caudal end
   2. Appendix testes: cranial end
2. In response to testosterone and DHT secreted by interstitial cells
   A. Mesonephric tubules near developing testes persist and connect rete testes -> efferent ductules
   
   1. 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

Question 6

Descent of testes

Answer 6

1. Pass ant ureters -> inguinal canal
2. Gubernaculum persists -> scrotal (testicular) lig
3. Cranial suspensory lig. Regresses

Question 7

Ovary dev

Answer 7

1. Dev in absence of TDF
   A. Rudimentary medullary cords form -> degrade -> replaced by vascular storms (intermediate mesoderm)
   B. Coelomic mesothelium -> cortical cords -> primordial follicles
   
   1. Surround PGCs and oogonia
   2. Oogonia arrested Prophase I -> primary oocyte
   3. Oogonia and primary oocyte number dec from atresia
   4. Birth: 1 million primordial follicles remain
      C. Tunica albuginea-> fibrous capsule under ovarian surface epithelium

Question 8

Female urogenital tracts and accessory glands dev

Answer 8

1. In absence androgenic hormones
   A. Mesonephric duct degenerates
   B. Vestiges may remain
   
   1. Epoophoron: cranial
   2. Paraoophoron: caudal
      A. Can form Gartner cyst is uterus/vagina (benign)
2. In absence AMH and facilitated by estrogen
   A. Paramesonephric ducts persist -> genital tract
   
   1. Uterine tubes from sup, unfused portions
   2. Uterovaginal canal from fusion at midline -> uterus, cervix, and vagina
   3. Broad lig from mesentery being dragged around
      B. Vaginal plate from sinus tubercle -> inf vagina and hymen
   4. Dev separate external openings
      C. Epithelial outgrowths urethra -> urethral and paraurethral glands
      D. Epithelial outgrowths UG sinus -> greater vestibular glands

Question 9

Descent of ovaries

Answer 9

1. Gubernaculum guides ovaries down -> lateral uterus
   A. Sup -> ovarian lig
   B. Inf -> round lig of uterus
2. Cranial suspensory lig -> suspensory lig of ovary
   A. Ovarian a. And v. Travel w/ it

Question 10

Indifferent stage dev external genitalia

Answer 10

1. 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
2. Posterior UG fold and genital swelling fuse at midline
   A. Cloacal membrane divides -> UG and anal membrane
   
   1. Urorectal septum
3. 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

Question 11

Male external genitalia dev

Answer 11

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

Question 12

Female external genitalia dev

Answer 12

1. Primordial phallus elongates internally and bends forward/inf externally w/ elongation ->
   A. Glans of clitoris
   B. Corpora cavernosa of clitoris
   C. Bulbs of vestibule
2. Urethral folds expand laterally -> labia minor
3. Urethral groove -> vestibule of vagina
4. Labioscrotal swelling -> labia majora and mons pubis
   A. Ant and post commisures

Question 13

Mesonephric duct derivatives

Answer 13

Males

1. Appendix of epididymis
2. Duct of epididymis
3. Ductus deferens
4. Seminal glands
5. Ejaculatory duct
6. Trigone of urinary bladder

Females

1. Addendum vesiculosa
2. Duct of epoophoron
3. Gartner duct
4. Trigone of bladder

Question 14

Mesonephric tubule derivatives

Answer 14

Males

1. Efferent ductules of testis
2. Paradidymis

Females

1. Epoophoron
2. Paroophoron

Question 15

Ureteric bud derivatives

Answer 15

Collecting systems both sexes

1. Ureter
2. Renal pelvis
3. Calices
4. Collecting ducts
5. Connecting tubules

Question 16

Metanephrogenic blastema derivatives

Answer 16

Excretory system both sexes

1. Bowman’s capsule
2. PCT
3. Descending and ascending limbs
4. DCT

Question 17

Urogenital sinus - vesical part derivatives

Answer 17

Urinary bladder (except trigone) in both sexes

Question 18

Urogenital sinus - pelvic part

Answer 18

Males

1. Prostatic urethra
2. Membranous urethra
3. Prostate gland

Females

1. Urethra
2. Urethral and paraurethral gland

Question 19

Urogenital sinus - phallic part derivatives

Answer 19

Males

1. Spongy urethra (except navicular fossa)
2. Bulbourethral gland

Females

1. Vestibule of vagina
2. Greater vestibular gland

Question 20

Sinus tuberacle derivatives

Answer 20

Males
1. Seminal colliculus w/ prostatic utricle

Females

1. Hymen
2. Vagina (inferior portion)

Question 21

Paramesonephric duct derivatives

Answer 21

Males
1. Appendix of testis

Females

1. Hydatid (of Morgagni)
2. Infundibulum
3. Uterine tube
4. Uterus
5. Cervix
6. Vagina (superior portion)

Question 22

Primordial germ cell derivatives

Answer 22

Males
1. Spermatagonia -> spermatozoa

Females
2. Oogonia -> oocytes

Question 23

Indifferent gonad derivatives

Answer 23

Males

1. Testes
2. Seminiferous tubules (w/ Sertoli cells)
3. Straight tubules
4. Rete testis
5. Interstitial cells of Leydig

Females

1. Ovary
2. Follicular cells
3. Thecae cells

Question 24

Gubernaculum derivatives

Answer 24

Males
1. Gubernaculum testis

Females

1. Ovarian ligament
2. Round ligament of uterus

Question 25

Superior suspensory ligament derivatives

Answer 25

Suspensory ligament of ovary

Question 26

Genital tubercle/primordial phallus derivatives

Answer 26

Males 1. Glans penis 2. Corpus cavernosa and crura of penis 3. Corpus spongiosum and bulb of penis Females 1. Glans clitoris 2. Body, angle, and crura of clitoris 3. Bulbs of vestibule

Question 27

Urogenital (urethral) folds derivatives

Answer 27

Males 1. Ventral part penis 2. Penile raphe Females 1. Labia minora

Question 28

Labioscrotal folds (genital swellings) derivatives

Answer 28

Males 1. Scrotum Females 1. Labia majora 2. Mons pubis