Embryology Flashcards
what occurs in gastrulation
formation of the trilaminar disc - invagination of the epiblast cells through the primitive streak to form the definitive endoderm and mesoderm
what are the 3 parts of the mesoderm
paraxial mesoderm
intermediate mesoderm
lateral plate
the urogenital system arises from _____
intermediate mesoderm
what is the name of the common cavity that the excretory ducts of the urogenital system enter
cloaca
when do primordial germ cells within the yolk sac migrate to the intermediate mesoderm
weeks 4-6
how are the genital ridges formed
coelomic epithelium proliferates and thickens to form genital ridges
proliferating epithelium will form somatic support cells which ________ forming the _____
envelope the PGCs forming primitive sex cords
what are the names of the 2 genital ducts
mesonephric (wolffian) duct
paramesonephric (mullerian) duct
what makes up the bipotential/ambisexual phase
development of the genital ducts and the indifferent gonads
when does sexual differentiation occur
from week 7 onwards
what triggers male development
presence of SRY transcription factor
in males what do somatic support cells develop into
sertoli cells
in males what do the primary sex cords form
testis/medullary cords which engulf the PGCs
what do the rete testis connect
the mesonephric tubules to the testis cords
what is the name of the thickened layer of connective tissue between the coelomic epithelium and testis cords
tunica albuginea
what stimulates the formation of sertoli cells
SRY
what do sertoli cells secrete
AMH (anti-mullerian hormone)
what does the AMH secreted by the sertoli cells do
causes the degenerative of the paramesonephric (mullerian) duct
sertoli cells stimulate gonadal ridge cells to form what
leydig cells
what do leydig cells secrete
testosterone
what does the testosterone secreted by the leydig cells do
induces formation of epididymis, vas deferens and seminal vesicles
what induces male specific external genitalia and prostate development
dihydrotestosterone (DHT)
what is persistent mullerian duct syndrome
mullerian (paramesonephric) duct fails to regress in males
how does persistent mullerian duct syndrome present
uterus, vagina and uterine tubes with male external genitalia
testes in ovarian location
how is persistent mullerian duct syndrome caused
mutations of AMH or AMH receptor genes
where do the testes originate
10th thoracic level
what pulls the testes caudally
gabernaculum
what is failure of one or both testes to descend called
crytorchidism
what is the tunica vaginalis made from
descended peritoneum
what are the 3 accessory glands in males
prostate
bulbourethral
seminal
when do the 3 accessory glands in males develop
week 10
from what does the seminal gland develop
mesonephric duct
how are the prostate and bulbourethral glands formed
endodermal invaginations from the urethra
the prostate is above/below the bulbourethral glands
above
from what does the vas deferens form
mesonephric duct
female development occurs in the absence of ___
SRY transcription factor
in females germ cells develop into ____ and then into ____
oogonia and then into primary oocytes
in females what differentiates into granulosa cells and surrounds the primary oocytes
somatic support cells
what duct degenerates in females
mesonephric (wolffian) - wolff is a boys name
what stimulates the formation of the female external genitalia and development of the paramesonephric ducts
ovarian oestrogens and from maternal sources
what do the paramesonephric (mullerian) ducts give rise to
uterine tubes
uterus
superior vagina
what is a Gartner’s cyst
remnant of mesonephric duct
what are the 3 parts of the paramesonephric duct
cranial portion
horizontal portion
caudal portion
what gives rise to the uterus and superior vagina
the fused caudal portion of the paramesonephric duct
what does the caudal portion of the paramesonephric duct fuse with
the paramesonephric duct on the opposite side
vacuolisation of the paramesonephric portion of the vagina and the sinuvaginal bulbs gives rise to what
vaginal lumen and the fornices
how is the spongy urethra formed in males
proximal to distal zipping of the urethral groove
then ectodermal ingrowth at the tip of the glans penis meets the spongy urethra
how is the foreskin (prepuce) formed
circular ingrowth of ectoderm around periphery of the glans
when is the foreskin formed
week 12
what is hypospadias
external urethral opening doesnt lie at the tip of the penis - lies in an abnormal position along the ventral aspect of the penis (varying degrees of severity)
when does the first trimester complete
12 weeks
when does the second trimester complete
28 weeks
when does the 3rd trimester complete
40 weeks
how long after fertilisation can pregnancy be detected by urine test
10 days
the Y chromosome has the sex determining region and causes the development of testes from the ______
bipotential gonad
fetal testes secrete _____
testosterone and mullerian inhibiting factors (AMH)
what causes the development of the male internal genital tract
testosterone and MIF (AMH)
in males the _____ ducts form the reproductive tract
wolffian (mesonephric)
in males the ____ ducts degenerate
mullerian (paramesonephric)
what is the bipotential gonad ridge
area of the embryo with potential to develop into male or female gonads
in the absence of testicular hormones a fetus will develop _____
female internal genital tract
when can you tell sex of fetus on scan
16 weeks