Embryology of the Reproductive tract

Question 1

what is gastrulation?

Answer 1

• formation of the trilaminar disc

Question 2

urogenital and reproductive systems arise from what embryological structure?

Answer 2

• intermediate mesoderm

Question 3

excretory ducts enter what common cavity?

Answer 3

• cloaca

Question 4

PCG’s (primordial germ cells) within the yolk sac migrate via what structure to the intermediate mesoderm (weeks 4-6)

Answer 4

• dorsal mesentry

Question 5

coelomic epithelium proliferates and thickens to form what?

Answer 5

• genital ridges

Question 6

proliferating epithelium will form somatic support cells which envelop what?

Answer 6

• the primordial germ cells
• this forms the primitive sex cords

Question 7

what are the 2 genital ducts?

Answer 7

• mesonephric (wolfian duct)
• paramesonephric (mullerian) duct

Question 8

what is the ambisexual/bipotential phase of development?

Answer 8

• 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

Question 9

germ cells differentiate into what first in the female?

Answer 9

• oogonia
• then into primary oocytes

Question 10

what do somatic support cells differentiate into

Answer 10

• granulosa cells and surround primary oocytes
  -> this forms primordial follicles in the ovary

Question 11

female gonad forms what two structures?

Answer 11

• primordial follicles
• thecal cells

influence of oestrogen stimulation formation of female external genitalia and development of paramesonephric ducts

Question 12

paramesonephric (mullerian) ducts give rise two what 3 parts?

Answer 12

• uterine tubes
• uterus
• superior vagina

Question 13

the paramesonephric duct has 3 parts

Answer 13

• cranial portion
• horizontal portion
• caudal portion

Question 14

what is paramesonephric duct

Answer 14

• 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

Question 15

the uterovaginal canal gives rise to what?

Answer 15

• uterus and superior vagina

Question 16

what is vaginal lumen created by?

Answer 16

• vacuolization of paramesonephric portion of the vagina and the sinuvaginal bulbs

Question 17

• some congenital abnormalities of uterus

Answer 17

study

Question 18

somatic support cells develop into what cells in the male?

Answer 18

sertoli cells

Question 19

the primary sex cords from testis/medullary cords, engulf what cells

Answer 19

• primordial gonadal cells

Question 20

rete testis connect mesonephric tubules to what cords

Answer 20

• testis cords - between coelomic epithelium and testis cords, a thickened layer of CT forms the tunica albuginea

Question 21

sertoli cells secrete what?

Answer 21

• AMH (anti-mullerian hormone) -> causing degeneration of the paramesonephric duct

Question 22

what else do sertoli cells do?

Answer 22

• stimulate gonadal ridge cells to form Leydig cells (testosterone)
• testosterone induces formation of epididymis, vas deferens, seminal vesicles

Question 23

what does dihydrotestosterone do?

Answer 23

induces male specific external development and prostate

Question 24

what thoracic level do testes originate?

Answer 24

• 10th thoracic level
• ‘pulled caudally’ by the gubernaculum
• failure to descend one or both testis is cryptorchidism

Question 25

what is persistent mullerian duct syndrome?

Answer 25

mullerian (paramesonephric) duct fails to regress

presents with:
- uterus, vagina and uterine tubes
- testes in ovarian location
- male external genitalia

Question 26

what week of development do 3 accessory glands develop near the junction of the mesonephric duct and urethra

Answer 26

• during week 10
  -> prostate and bulbourethral glands, seminal vesicle

Question 27

what is the prostate and bulbourethral glands?

Answer 27

• endodermal invaginations from the urethra
• prostate above the bulbourethral glands

Question 28

what does seminal vesicle develop from?

Answer 28

• mesonephric duct

Question 29

how does spongy urethra form?

Answer 29

• by proximal to distal zipping of urethral groove
• ecrodermal ingrowth at tip of the glans penis - meets spongy urethra

Question 30

which week is prepuce (foreskin) formed?

Answer 30

• week 12, it is formed by a circular ingrowth of ectoderm around the periphery of the glans

Question 31

what is hypospadias?

Answer 31

• external urethral opening lies in an abnormal position along the ventral aspect of the penis, occurs w varying degrees of severity