Female UG Embryology (Week 7--Trelease)

Question 1

Same as male GU development, but what are 3 overlapping kidney systems formed from intermediate mesoderm?

Answer 1

Pronephros

Mesonephros

Metanephros

Question 2

Pronephros

Answer 2

Disappears by end of 4th week

Question 3

Mesonephros

Answer 3

Most disappears

Males have Wolffian ducts from mesonephros, but in females these DISAPPEAR

Paramesonephric (Mullerian) ducts form lateral to mesonephric ducts and also empty into cloaca

Gonads and urogenital ridges

Question 4

Metanephros

Answer 4

Definitive kidney; same as male

Uretic bud forms collecting system: ureter, renal pelvis, major calyces then subdivides to form minor calyces then renal pyramids, collecting tubules (from week 5 to month 5)

Metanephric tissue cap (metanephric mesoderm) forms nephron: glomeruli, Bowman’s capsules, joins collecting duct of uretic bud to form DCT, loop of Henle, PCT

Question 5

Ovarian development

Answer 5

In females, primitive sex cords dissociate into irregular cell clusters containing primitive germ cells in primitive ovarian medulla (later replaced by vascular stroma)

Second generation cortical cords

Cell clusters form follicular cells and germ cells form oogonia

Question 6

Female genital ducts

Answer 6

Paired paramesonephric (Mullerian) ducts form main genital ducts

Caudal vertical parts of ducts fuse to create uterine canal, then the broad ligament of the uterus is established

Ovary is posterior

Fused paramesonephric ducts form endometrium of corpus (body) and cervix

Surrounding mesenchyme forms myometrium

Question 7

How does the vagina form?

Answer 7

After caudal tip of fused paramesonephric ducts reaches UG sinus, 2 evaginations (sinovaginal bulbs) grow to form vaginal plate

Vagina becomes cannalized at month 5, and get vaginal fornices

Upper vaginal canal is uterine (paramesonephric) origin

Lower vaginal canal is from UG sinus (cloacal or endodermal)

Question 8

Uterus developmental defects

Answer 8

Uterus didelphys with double vagina

Uterus arcuatus (indentation at top)

Uterus bicornis (M shaped)

Uterus bicornis with 1 rudimentary horn (half cut off)

Atresia of cervix (cervix permanently closed)

Atresia of vagina (vagina fused shut)

Question 9

Female external genitalia

Answer 9

Estrogens stimulate development of external genitalia

Genital tubercle elongates to form clitoris

Urethral folds don’t fuse (like in males) and form labia minora

Genital swellings enlarge to form labia majora with open UG groove forming vestibule

Question 10

Descent of the ovaries and ligaments

Answer 10

Ovaries only descend a short way to end up just below rim of true pelvis

Cranial genital ligament becomes suspensory ligament of the ovary (infundibulopelvic ligament)

Caudal genical ligament becomes ovarian ligament and round ligament of the uterus