genital symtem

• Reproductive system


  Consists of the gonads, internal duct system and external genitalia
• Development of the reproductive system

  1. Transition through an indifferent stage

  2. Sexual differentiation stage
• Most reproductive anomalies involve some combination of intersex development and appearance
• Development of Gonads

  1. Indifferent stage

  2. Sexual differentiation stage (male embryo)

  3. Sexual differentiation stage (female embryo)
• Indifferent stage

  • Formation of gonadal ridge
  • Incorporation of supporting and primordial germ cells into the gonadal ridge
  • Formation of gonadal cords
• Sexual differentiation stage (male)

  • Gonadal cords form solid tubules that contain the primordial germ cells
  • Primordial germ cells within seminiferous cords differentiate into spermatogonia
  • Supporting cells differentiate into sustentacular (Sertoli) cells
  • Supporting cells become two populations of interstitial cells
• Sexual differentiation stage (female)

  • Gonadal cords reorganize into small clusters with individual germ cells surrounded by follicular cells
  • Primordial follicles in the outer cortex are retained
  • Primordial germ cell inside the primordial follicle differentiates into oogonium
• Development of the Internal Duct System

  1. Indifferent stage

  2. Sexual differentiation stage (male)

  3. Sexual differentiation stage (female)
• Indifferent stage


  • Presents paired mesonephric (Wolffian) ducts and paramesonephric (Mullerian) ducts
• Sexual differentiation stage (male)

  • Paramesonephric ducts regress
  • Mesonephric duct becomes ductus epididymis and ductus deferens
• Sexual differentiation stage (female)

  • Mesonephric ducts fail to develop
  • Paramesonephric ducts form uterine tube, uterine horns, uterine body, uterine cervix, and cranial third of vagina
  • Vagina has dual origin - cranial one-third from paramesonephric ducts, caudal two-thirds from vaginal plate
• Development of Male Accessory Glands

  1. Prostate, bulbourethral and lateral urethral glands develop from evaginated epithelium of urogenital sinus

  2. Vesicular glands arise from evaginated epithelium of mesonephric duct
• Development of Female Accessory Glands

  Derived only from the evaginated epithelium of the urogenital sinus
• Development of Mammary Glands

  In both sexes, a mammary ridge (milk line) forms along the ventral body wall
• Development of vaginal lumen

  Degeneration of the center of the solid tubercle
• Hymen


  Persists where the vagina joins the urogenital sinus
• Development of male accessory glands

  1. Prostate, bulbourethral and lateral urethral glands develop from evaginated epithelium (endoderm) of urogenital sinus

  2. Vesicular gland (seminal vesicle) arises from evaginated epithelium (mesoderm) of the caudal mesonephric duct

  3. Gland smooth muscle comes from surrounding mesenchyme
• Development of female accessory glands

  1. Derived only from the evaginated epithelium of the urogenital sinus

  2. These glands are the urethral and major and minor vestibular glands

  3. Vestibular glands are female homologues of male bulbourethral glands
• Development of mammary glands

  1. Mammary ridge (line) of thickened ectoderm forms bilaterally

  2. Mammary buds develop periodically along the ridge

  3. Buds determine the number and locations of mammary glands

  4. Ectoderm induces proliferation of underlying mesoderm (teat formation)

  5. Mesoderm induces epithelial cell proliferation

  6. Epithelial cell cords invade underlying mesoderm and eventually canalize to form epithelial lined lactiferous ducts

  7. Number of cell cord invasions and subsequent lactiferous duct systems per teat is species dependent
• Formation of ligaments

  1. Genital fold becomes male or female genital ligaments

  2. In females, genital fold becomes suspensory ligament of the ovary, mesovarium, mesosalpinx, and the cranial part of the mesometrium

  3. Caudal part of the mesometrium is formed by the tissue "shelf' that accompanies each paramesonephric duct

  4. In males, genital fold becomes mesorchium and mesoductus deferens

  5. Inguinal fold becomes the proper ligaments of the ovary and round ligament of the uterus in females

  6. In males, inguinal fold gives rise to the gubernaculums of the fetus which subsequently in the adult becomes the proper ligament of the testis and ligament of the tail of the epididymis
• Descent of the gonad

  1. Caudal shift of the gonad from its original position

  2. In females, the ovary remains intra-abdominal and the extent of caudal shift is species dependent

  3. In males the testis descends to the inguinal region

  4. Testes bulge into the coelom pushing their peritoneal (somatic mesoderm) covering

  5. Cranial fold becomes the diaphragmatic ligament of mesonephros and the caudal fold, the inguinal ligament of mesonephros

  6. Gubernaculum originates as a condensation of the mesenchyme within each inguinal fold

  7. Under the influence of gonadotropins and testicular androgens, the gubernaculum accumulates fluid and become a gel mass

  8. Swollen gubernaculum enlarges the future inguinal canal

  9. Traction created by subsequent outgrowth of the scrotal wall and dehydration of the guberaculum passively pulls the testis to the inguinal canal

  10. Peritoneum (somatic mesoderm) reflected over the testes becomes the visceral tunica vaginalis while the peritoneum that lines the scrotal pouch becomes the parietal tunica vaginalis
• Development of the external genitalia

  1. Indifferent stage: Bilateral urogenital folds, genital tubercle, bilateral genital (labioscrotal) swellings

  2. Male embryo: Urogenital folds => penile urethra, urogenital orifice elongates along with the phallus forming a urogenital groove, penile urethra created when the groove closes, right and left genital folds fuse in the midline to form the genital raphe

  3. Female embryo: Urogenital folds => labia minora of the vulva, urogenital orifice => vulval cleft, urogenital sinus => vestibule, genital tubercle => clitoris, genital swellings degenerate
• Paramesonephric duct atresia (White heifer disease) consists of the absence of the paramesonephric duct derived parts of the female tract (oviducts, uterus, cervix and vagina)
• Ovaries are normal in paramesonephric duct atresia. The cause is unknown. Not limited to white cattle.
• Hypospadia - failure of urethral folds to fuse resulting in an opening of the urethra on the ventral surface of the penis
• Double cervix — results from lack of fusion of the paramesonephric ducts beyond the body of the uterus. It may present parturition difficulties.