Embryology of the Reproductive tract Flashcards
what is gastrulation?
- formation of the trilaminar disc
urogenital and reproductive systems arise from what embryological structure?
- intermediate mesoderm
excretory ducts enter what common cavity?
- cloaca
PCG’s (primordial germ cells) within the yolk sac migrate via what structure to the intermediate mesoderm (weeks 4-6)
- dorsal mesentry
coelomic epithelium proliferates and thickens to form what?
- genital ridges
proliferating epithelium will form somatic support cells which envelop what?
- the primordial germ cells
- this forms the primitive sex cords
what are the 2 genital ducts?
- mesonephric (wolfian duct)
- paramesonephric (mullerian) duct
what is the ambisexual/bipotential phase of development?
- this is the first differentiation stage
- the development of genital ducts -> mesonephric and paramesonephric ducts
- genital ducts and indifferent gonads mark the ambisexual phase of development - gonads are morphologically indistinguishable early in development
- sexual differentiation occurs from week 7 onwards
germ cells differentiate into what first in the female?
- oogonia
- then into primary oocytes
what do somatic support cells differentiate into
- granulosa cells and surround primary oocytes
-> this forms primordial follicles in the ovary
female gonad forms what two structures?
- primordial follicles
- thecal cells
influence of oestrogen stimulation formation of female external genitalia and development of paramesonephric ducts
paramesonephric (mullerian) ducts give rise two what 3 parts?
- uterine tubes
- uterus
- superior vagina
the paramesonephric duct has 3 parts
- cranial portion
- horizontal portion
- caudal portion
what is paramesonephric duct
- paired ducts of embryo that run down lateral sides of the genital ridge and terminate at the sinus tubercle in the primitive urogenital sinus
- in female - they will develop into the uterine tubes, uterus and cervix and upper 1/3 of vagina
the uterovaginal canal gives rise to what?
- uterus and superior vagina
what is vaginal lumen created by?
- vacuolization of paramesonephric portion of the vagina and the sinuvaginal bulbs
- some congenital abnormalities of uterus
study
somatic support cells develop into what cells in the male?
sertoli cells
the primary sex cords from testis/medullary cords, engulf what cells
- primordial gonadal cells
rete testis connect mesonephric tubules to what cords
- testis cords - between coelomic epithelium and testis cords, a thickened layer of CT forms the tunica albuginea
sertoli cells secrete what?
- AMH (anti-mullerian hormone) -> causing degeneration of the paramesonephric duct
what else do sertoli cells do?
- stimulate gonadal ridge cells to form Leydig cells (testosterone)
- testosterone induces formation of epididymis, vas deferens, seminal vesicles
what does dihydrotestosterone do?
induces male specific external development and prostate
what thoracic level do testes originate?
- 10th thoracic level
- ‘pulled caudally’ by the gubernaculum
- failure to descend one or both testis is cryptorchidism
what is persistent mullerian duct syndrome?
mullerian (paramesonephric) duct fails to regress
presents with:
- uterus, vagina and uterine tubes
- testes in ovarian location
- male external genitalia
what week of development do 3 accessory glands develop near the junction of the mesonephric duct and urethra
- during week 10
-> prostate and bulbourethral glands, seminal vesicle
what is the prostate and bulbourethral glands?
- endodermal invaginations from the urethra
- prostate above the bulbourethral glands
what does seminal vesicle develop from?
- mesonephric duct
how does spongy urethra form?
- by proximal to distal zipping of urethral groove
- ecrodermal ingrowth at tip of the glans penis - meets spongy urethra
which week is prepuce (foreskin) formed?
- week 12, it is formed by a circular ingrowth of ectoderm around the periphery of the glans
what is hypospadias?
- external urethral opening lies in an abnormal position along the ventral aspect of the penis, occurs w varying degrees of severity
