Embryology of the Reproductive System Flashcards
What happens during gastrulation?
Formation of the trilaminar disc
- invagination of the epiblast cells through the primitive streak to form the definitive endoderm and mesoderm
What happens to the mesoderm during gastrulation?
Organised into 3 main groups: paraxial, intermediate and lateral plate
What does the urogenital system arise from?
Intermediate mesoderm
What is the cloaca?
Excretory ducts of both the urinary and genital system enter a common cavity
When and where do primordial germ cells within the yolk sac migrate?
Migrate via dorsal mesentery to intermediate mesoderm (weeks 4-6)
What forms genital ridges?
Coelomic epithelium proliferates and thickens
What forms somatic support cells in the indifferent gonad?
Proliferating epithelium
What is the role of somatic support cells in the indifferent gonad?
Envelop the primordial germ cells
What happens in the ambisexual/bipotential phase?
The development of the genital ducts
- mesonephric (wollfian) duct
- paramesonephric (mullerian) duct
Where do both genital ducts connect to?
Posterior wall of the urogenital sinus
When does sexual differentiation occur?
From week 7 onwards
What triggers male development?
Presence of SRY (sex determining region of Y) transcription factor
In male development somatic support cells develop into….
Sertoli cells
In males primary sex cords form ______/_______ _____, which engulf the ___.
In males primary sex cords form testis/medullary cords, which engulf the PGC’s.
Rete testis connect the ________ ______ to the _____ _____.
Rete testis connect the mesonephric tubules to the testis cords.
Between the ______ ______ and testis cords, a thickened layer of connective tissue forms the _____ _______.
Between the coelomic epithelium and testis cords, a thickened layer of connective tissue forms the tunica albuginea.
SRY protein stimulates the formation of what?
Sertoli cells
Sertoli cells secrete ___ which causes the degeneration of the __________ ____.
Sertoli cells secrete AMH which causes the degeneration of the paramesonephric duct.
Sertoli cells stimulate _______ ____ to form Leydig cells. Leydig cells secrete _______.
Sertoli cells stimulate gonadal ridge to form Leydig cells. Leydig cells secrete testosterone.
Testosterone induces the formation of which three structures?
Epididymis
Vas deferens
Seminal vesicles
Dihydrotestosterone induces male specific ______ _________ development and _______.
Dihydrotestosterone induces male specific external genitalia development and prostate.
What causes persistent mullerian duct syndrome
Mutations of AMH or AMH receptor genes
Paramesonephric ducts fail to regress
Describe the presentation of persistent mullerian duct syndrome?
Present with
- uterus, vagina and uterine tubes
- testes in ovarian location
- male external genitalia
The testes originate at ____ thoracic level and are pulled caudally by the _________.
The testes originate at 10th thoracic level and are pulled caudally by the gubernaculum.
Failure to descend of one or both testes is ________
Failure to descend of one or both testes is cryptoorchidism
3 accessory glands spout near the junction of the mesonephric duct and urethra during week 10, what are the three glands?
Prostate and bulbourethral glands
Seminal vesicle
The prostate sits _____ the bulbourethral glands
The prostate sits above the bulbourethral glands
The seminal vesicle develops from what structure?
Mesonephric duct
Female development occurs in the absence of what?
SRY transcription factor
In female development germ cells differentiate into ______ and then into _______ ________.
In female development germ cells differentiate into oogonia and then into primary oocytes.
In female development ______ ______ cells differentiate into granulosa cells and surround the _______ _______.
In female development somatic support cells differentiate into granulosa cells and surround the primary oocytes.
Granulosa surrounding the primary oocytes form?
Primordial follicles in the ovary
What are thecal cells?
Leydig homolog
what influences the development of female external genitalia and development of paramesonephric ducts?
ovarian oestrogens from maternal sources
What does the paramesonephric duct give rise to?
Uterine tubes
Uterus
Superior vagina
What is a gartners cyst?
Remnant of mesonephric duct
What are the three parts of the paramesonephric (mullerian) duct?
Cranial portion- opens into the coelomic cavity
Horizontal portion- crosses the mesonephric duct
Caudal portion- which fuses with the paramesonephric duct on the opposite side
What does the fused portion of the paramesonephric ducts give rise to?
The uterus and superior vagina
How is the vaginal lumen created?
By vacuolisation of the paramesonephric portion of the vagina and the sinuvaginal bulbs
What are some of the complications that can occur in female development?
Double uterus & double vagina
Double uterus
Bicornate uterus
Sepatated uterus
Unicornate uteris
Cervical atresia
Between week _-_ the external genitalia are indistinguishable
Between week 4-7 the external genitalia are indistinguishable
How is the spongy urethra formed?
Spongy urethra forms by proximal to distal zipping of urethral groove
How is the spongy urethra completed at the distal penis?
Ectodermal ingrowth at tip of glans which meets spongy urethra
How is the prepuce formed?
Circular ingrowth of the 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
