Reproductive System Embryology 生物及解剖學科 陳 瀅 18749 ychen0523@ndmctsgh.edu.tw

Study Goals Development of gonads Development of genital ducts Development of external genitalia Development of inguinal canal

Development of gonads 7th week indifferent state of sexual development The gonads are derived from three sources The mesothelium lining the posterior abdominal wall The underlying mesenchyme The primordial germ cells

Development of gonads 5th week 6th week 7th week

Development of gonads gonadal ridge primordial germ cell are visible in 4th week among the endodermal cells of the yolk sac migrate along the dorsal mesentary of the hindgut to the gonadal ridges

Development of gonads Sex determination (after 7th week) male – Y chromosome, which has a testis-determining factor (TDF) female – XX chromosome

Development of gonads with the TDF gonadal cord  seminiferous cords without the TDF formation of ovaries the type of gonads  determine the type of sexual differentiation (genital ducts and external genitalia)

Development of gonads Testes gonadal cords condense and extend into the medulla  seminiferous cords rete testis tunica albuginea – a thick fibrous capsule suspended by its own mesentery – mesorchium

Development of gonads Testes interstitial cells (Leydig) 8th week, the cells begin to secrete androgenic hormones – testosterone and androstenedione human chorionic gonadotrophin (hCG) peak amount 8-12 week Mullerian inhibiting substance (MIS)

Development of gonads Testes Sertoli cell derived from the surface epithelium of the testis MIS spermatogonia primordial sperm cells derived from the primordial germ cell

Development of gonads E43 days new born 21 weeks

Development of gonads Ovaries gonadal cords extend into the medulla  rete ovarii cortical cords from surface epithelium 16 week  primordial follicles, each of which consists of an oogonium (surrounded by follicular cells from surface epithelium)

Development of gonads Ovaries No oogonia form postnatally (2 million) the surface epithelium called “germinal epithelium” germ cells derived from the primordial germ cells the ovary is suspended by a mesentary – the mesovarium

Development of gonads E43 days new born 14 days

Development of genital ducts 5th – 6th weeks, both pairs of genital ducts are present in the indifferent state Mesonephric ducts play an essential role in male reproductive system Paramesonephric ducts play an essential role in female reproductive system

Development of genital ducts

Development of genital ducts male genital ducts and glands testosterone Mullerian inhibiting substance (MIS)

Development of genital ducts male genital ducts and glands prostate gland endodermal cells mesenchyme – stroma and smooth muscles

Development of genital ducts

Development of genital ducts female genital ducts and glands Without testosterone and MIS  mesonephric ducts regress  paramesonephric ducts develop The endometrial stroma and myometrium are derived from splanchnic mesenchyme and upper part of vagina

Development of genital ducts

Development of genital ducts female genital ducts and glands

Development of genital ducts vagina the endoderm of the urogenital sinus  epithelium surrounding mesenchyme  fibromuscular wall

Development of genital ducts vagina Sinus tubercle  sinovaginal bulbs  vaginal plate The central cells in the plate break down forming the lumen of vagina

Development of genital ducts vagina uterovaginal primordium + urogenital sinus

Anomaly of genital ducts

Development of external genitalia 4th – 7th weeks

Development of external genitalia 9 weeks 11 weeks 12 weeks

Development of external genitalia male female male 7 weeks 10 weeks 10 weeks

Development of external genitalia female Congenital adrenal hyperplasia (CAH)

Androgen insensitivity syndrome also called the testicular feminization syndrome normal-appearing female, despite the presence of testis and a 46, XY chromosome

Anomaly of external genitalia Hypospadias

Anomaly of external genitalia congenital absence

Anomaly of external genitalia Vaginal atresia

Development of inguinal canals mesonephros  gubernaculum  labioscrotal swellings peritoneum  inguinal canal 7 weeks 28 weeks

Ectopic testes

Congenital inguinal hernia

References Moore Persaud : The Developing Human 9th edition, 2012 Langman’s : Medical Embryology 11th edition, 2010