Indifferent gonads

• A genital ridge forms from intermediate mesoderm (medial to mesonephros) – forms stroma of gonads
• Primitive sex cords form from mesodermal coelomic epithelium covering the genital ridge
• Primordial germ cells (endodermal) develop in wall of yolk sac ⇒ pass through dorsal mesentery ⇒ lie inbetween primitive sex cords
• Gonads don’t acquire male or female characteristics until week 7

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Testis

• Primitive sex cords branch and anastomose to from testis cordis
• Primordial germ cells incorporate in the testis cordis
• Testis cordis lose connection with the surface epithelium – form seminiferous tubules
• Straight ends of seminiferous tubules anastomose at hilum of testis and form rete testis
• Rete testis connect to mesonephric duct via 8-12 mesonephric tubules – forms head of epididymis
• Surface epithelium disappears, testis surrounded by thick fibrous capsule – tunica albuginea

Descent of testis:

• Testis develop on posterior abdominal wall behind peritoneum
• A gubernacular cord extends from lower pole of testis to scrotal pouch
• Gubernacular cord shortens due to chorionic gonadotropins and increased intraabdominal pressure
• Goes through inguinal canal
• Remnant of gubernaculum disappears
• An evagination of peritoneal cavity called vaginal process enters scrotum
• Forms serous cavity for testis called tunica vaginalis
• Proximal part of vaginal process obliterated

Anomalies of testis:

1. Cryptorchidism – undescended testis
2. Maldescended testis – lying somewhere over the normal line of descent
3. Ectopic testis – outside that line
4. Congenital inguinal hernia – failure of obliteration of proximal vaginal process

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Male genital ducts

1. Mesonephric tubules:

• Upper – degenerate, form appendix of epididymis
• Middle – 6-12 form head of epididymis and are connected to rete testis
• Lower – degenerate, form paradidymis

2. Mesonephric duct:

• Body and tail of epididymis
• Vas deferens
• Seminal vesicle
• Ejaculatory duct

3. Mullerian duct (notes in female):

Degenerates completely except the upper end – forms appendix of testis

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Ovaries

• Primitive sex cords break into clusters of cells – form primary medullary cords
• Which is replaced by vascular stroma to form – medulla of ovary
• Coelomic epithelium proliferates again – forms 2nd generation of ovary (sex) cords
• Which will divide into clusters of cells – follicular cells of primary follicle
• Primordial germ cells incorporate into primary follicles – form oogonia
• Primitive cortex becomes secondary cortex containing primary follicles
• Medulla is just vascular stroma, no follicles

Descent of ovaries:

• Ovary develops in posterior abdominal wall
• Gubernacular cord from lower pole of ovary to labia majora
• Pulls ovary to its level on pelvis
• Uterus develops, gubernaculum divides into 2 parts:

1. Ovarian ligament – ovary to uterus
2. Round ligament – uterus to labia majora (goes through inguinal canal)

Congenital anomalies of ovaries:

1. Congenital absence – Turner’s syndrome
2. True hermaphroditism – gonads of both sex present
3. Imperfect descent – in inguinal canal
4. Vagina agenesis

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Female genital ducts

• 2 mullerian (paramesonephric) ducts arise from coelomic epithelium, lateral to mesonephric ducts
• Grow caudally, curve medially infront of mesonephric duct, meet each other and grow caudally

• The 2 ducts fuse to form uterovaginal canal
• The lower tip of uterovaginal canal grows downwards and protrudes posterior wall of urogenital sinus
• 2/3 of mullerian ducts form oviducts
• Uterovaginal canal forms uterus and upper 4/5 vagina
• Where the 2 ducts unite, forms fundus of uterus
• Lower 1/5 vagina forms from definitive urogenital sinus

Union between upper 4/5 and lower 1/5 vagina is demarcated by hymen

Mesonephric tubules and mesonephric duct degenerates

Congenital anomalies:

1. Double uterus, double vagina – complete failure of fusion
2. Double uterus, single vagina – partial failure of fusion
3. Agenesis of uterus – failure of both mullerian ducts to develop
4. Rudimentary horn – failure of one mullerian ducts to develop, therefore one fallopian tube, and half body of uterus connected to rudimentary horn
5. Atresia of cervix/vagina
6. Imperforate hymen – cells between junction fail to degenerate
7. Remnants of mesonephric tubules – enlarge and form cysts
8. Remnants of mesonephric duct – Gartner’s duct
9. Infantile uterus – small uterus, large cervix