Overview
This lecture covers the embryological development of female reproductive organs, including the ovaries, internal and external genitalia, and associated ducts.
Development of Female Internal Genitalia
- The müllerian (paramesonephric) duct forms the fallopian tubes, uterus, cervix, and upper two-thirds of the vagina.
- The wolffian (mesonephric) duct regresses, leaving remnants like paroophoron, epoophoron, and Gartner's duct.
Development of Ovary
- Ovaries develop from the genital ridge, specifically the middle part.
- Germ cells migrate from the yolk sac to the genital ridge and reach maximum number at 20 weeks.
- Ovaries descend into the pelvis between the 7th and 9th months of fetal life.
- The gubernaculum connects the ovary to the labia majora and forms the ovarian and round ligaments.
Formation of Uterus and Fallopian Tubes
- Three main steps: formation of two müllerian ducts, their fusion, and dissolution of the intervening septum.
- Ducts fuse between weeks 7-12 of embryonic life; septum disappears by the 5th month.
Development of Vagina
- Upper two-thirds of the vagina develop from the müllerian duct; lower one-third from the urogenital sinus.
- Fusion forms a solid vaginal plate, canalized by week 20.
- Failure of canalization leads to transverse vaginal septum.
Development of Vulva (External Genitalia)
- Clitoris develops from the genital tubercle.
- Labia minora from genital folds; labia majora from genital swellings.
- Hymen forms from junction of müllerian tubercle and urogenital sinus.
- Bartholin glands develop from the urogenital sinus.
Fate of Wolffian Duct Remnants
- Cranial remnant: epoophoron (organ of Rosenmüller).
- Caudal remnant: paroophoron; Gartner's duct may persist in vaginal wall (Gartner cyst).
Disorders and Genital Asymmetry
- Genital asymmetry may indicate mixed gonadal dysgenesis (usually 45X/46XY mosaicism).
- Features: asymmetrical gonads, atypical genitalia, clitoromegaly, labial/scrotal fold differences.
Key Terms & Definitions
- Müllerian duct (paramesonephric) — precursor to female internal genital organs.
- Wolffian duct (mesonephric) — regresses in females, remnants may persist.
- Gubernaculum — ligament guiding gonadal descent.
- Gartner's duct — remnant of the wolffian duct in females.
- Genital Ridge — embryonic structure giving rise to gonads.
Action Items / Next Steps
- Review embryological timelines (weeks of development for each structure).
- Study diagrams of female reproductive tract development.
- Prepare for quiz on reproductive embryology key terms.