Urogenital System

• Briefly describe development of the metanephric kidney system
  • The Ureteric bud elongates and penetrates the metanephric blastema
  • Reciprocal induction between the ureteric bud and metanephric blastema forms the permanent kidneys
    • Stalk of the ureteric bud → ureter
    • Cranial part of ureteric bud → collecting tubules, major calices, minor calices
    • Metanephrogenic blastema → nephron
• State the embryological basis for the following anomalies: multicystic dysplastic kidney, duplication of the ureter, accessory renal artery, horse-shoe shaped kidney, pelvic kidney
  • Multicystic dysplastic kidney
    • Dysmorphology of the renal system
  • Duplication of the ureter
    • The ureteric bud divides abnormally
  • Accessory renal artery
    • The renal arteries perisist as the kidney ascends the pelvis
  • Horse-shoe shaped kidney
    • The migration of nephrogenic cells is impaired causing the inferior poles of the kidneys fuse
  • Pelvic kidney
    • The Kidney fails to ascend from the pelvis
• Briefly describe the development of the adrenal gland and state an associated congenital anomaly Development
  • Mesenchyme → Develops into the adrenal cortex
  • Neural Crest cells → Develop into the adrenal medulla
  • Neural crest cells form a mass on the medial side of the embryonic cortex and differentiate into secretory cells of the medulla
  • The medulla is surrounded by the cortex
  • More mesenchymal cells arise from the mesothelium and enclose the cortex, forming the permanents cortex of the adrenal gland
  Congenital anomaly
  • Congenital Adrenal Hyperplasia and the adrenogenital syndrome
• Briefly describe the development of external genitalia in both sexes Male
  • Testosterone → is resonsible for the masculinization of the indifferent external genitalia
  • Primordial phallus → elongates to form the penis
  • Urethral folds → fuse to form the spongy urethra on the ventral penis
  • Surface ectoderm → fuses in the median plane to form the penile raphe
  • Ectodermal cord → grows towards the root of the penis and meets the spongy urethra, canalizes and completes the external urethra orifice
  • Phallic mesenchyme → corpus cavernosum and corpus spongiosum
  • Labioscrotal swellings → scrotum
  Female
  • Primordial phallus → clitoris
  • Urethral folds → fuse posteriorly to form the frenulum of the labia minora
  • Unfused part of urogenital folds → labia minora
  • Fused labioscrotal folds → fuse to form posterior and anterior labial commissure and mons pubis
  • Unfused labioscrotal folds → labia majora
• Briefly describe the development of the genital ducts in both sexes Male
  • Mesonephric ducts → male genital ducts
  • Proximal mesonephric duct → epididymis
  • Persistent mesonephric tubules → efferent ductules
  • Distal mesonephric duct → vas deferens after acquiring smooth muscles
  • Caudal mesonephric duct → seminal vesicles
  • Mesonephric duct between the duct of the seminal gland and urethra → ejaculatory duct
  • Endoderm of the prostatic urethra → glandular epithelium of prostate
  • Endoderm of the spongy urethra → bulbourethral gland
  Female
  • Mesonephric duct → degenerates because of low testosterone
  • Paramesonephric duct → develop because of the absence of MIS
  • Cranial paramesonephric duct → uterine tubes
  • Caudal fused paramesonephric duct → uterovaginal primordium
  • Uterovaginal primordium → uterus and vagina
  • Splanchnic mesenchyme → endometrial stroma and myometrium
• Briefly describe the development of the gonads in both sexes Male
  • Testis determining factor – induces testes formation
  • MIS → suppresses paramesonephric duct formation
  • Seminiferous cords → rete testis, seminiferous tubules, tubules recti (straight tubules)
  • Mesenchyme separating the seminiferous tubules → intersitial cells of leydig
  • Surface epithelium of testis → sertoli cells
  • Primordial germ cells → spermatozoa
  Females
  • Gonadal cords → rete ovarii
  • Cortical cords → primordial follicles
  • Primordial germ cells → oogonia

Distinguish between hermaphrodites and pseudohermaphrodites