REB Embryology Flashcards
where do germ cells develop?
wall of yolk sac
when do germ cells begin migrating?
3 weeks
where does the early (indiffernt) gonad develop
on the urogenital ridge
where do germ cells migrate to?
genital ridge (specifically the primitive sex cords)
when do germ cells invade the gonad?
week 6
the urogenital ridge is covered by epithelial cells of what origin?
mesodermal
formation of primitive sex cords
the primitive sex cords extend from epithelium and penetrate into the ridge
which duct degenerates in females
mesonephric duct
which duct degenerates in males
paramesonephric duct
what duct forms the ductus (vas) deferens
mesonephric duct
what is the mullerian duct
paramesonephric duct
what is the wolffian duct
mesonephric duct
what duct invaginates the epithelium
paramesonephric duct
what is the determining factor of sex of the baby
Y chromosome
SDR (sex determining region)
protein product of SDR - testis determining factor
what is the effect of y influence on the medullary cord, cortical cords and the tunica albuginea
medullary cord develops (testis cord)
no cortical cords
thick tunica albuginea
passage of sperm
seminiferous tubules –> rete testis (network of tubules) –> efferent ductules –> epididymis –> ductus (vas) deferens –> base of bladder
connections of the rete testis cords develop between the
testis cords and the mesonephric cords
what structure does the seminiferous tubules arise from?
(horseshoe-shaped loops of) testis cords
what are the major cell types of the testis and what is their purpose in the development of the fetus
leydig cells - produce testosterone - mesonephric ducts stimulates (ductus deferens, epididymis formed)
sertoli cells - Mullerian inhibiting substance which causes the paramesonephric ducts to degenerate
what causes the paramesonephric ducts to degenerate
Mullerian inhibiting substance from sertoli cells of the testis
what structures are made from the mesonephric duct in males
epididymis
ductus deferens
runs to urethra
what structures are made from the paramesonephric duct in males
(small remnants)
appendix testis
prostatic utricle
what important structure is made by the mesonephric duct and is found in both males and females
ureteric buds
the mesonephric ducts come together at the posterior bladder wall and the ureteric buds extend to form ureters at the upper corners
these ducts form what structure/part of the bladder?
trigone
what is the significance of the growth pattern of the mesonephric duct in relation to the ureter in a male
the mesonephric duct loops around the ureter and enters the prostatic urethra (vas deferens and ejaculatory duct)
significance of the gubernaculum
mesenchymal cord attached to the lower pole of the gonad that ‘pulls’ the gonads down
blood supply for the gonads
L1/2
compare the end point of the descent of the gonads in males and females
males - down to scrotum (temperature control)
females - ends in the pelvis
The spermatic cords follow the gonads which follow the gubernaculum. the gubernaculum eventually degenerates. where does the spermatic cord end up?
inguinal canal
what is the anatomical relation of the processus vaginalis to the gubernaculum and the testis
anterior to the gubernaculum and the testis
what is the processus vaginalis
evagination of the peritoneum
what does the processus vaginalis persist as
tunica vaginalis
what is cryptorchidism
undescended testes
what are the possible sites of cryptorchidism
intra-abdominal
inguinal canal
ectopic (a place where it should not be)
what is orchidopexy? when should it be done?
correction of cryptorchidism
6-12 months old
when should the testes descend by?
3 months
the patent (opening) of the processus vaginalis can lead to
congenital and indirect inguinal herniation
what is a hydrocele. how is it identified?
collection of fluid in the tunica vaginalis
transillumination (lights up with torch)
what embryological structure does oogonia arise from? what does oogonia give rise to?
germ cells
primary oocytes
what does the paramesonephric duct form?
uterine tube
uterus
cervix and upper vagina
what are the remnants of the mesonephric duct is females?
small remnants in broad ligament
gartner’s cyst (may fill with fluid)
ureteric bud
what part of the female reproductive organ is innervated by the deep perineal nerve?
lower vagina and hymen (structures from the vaginal plate)
what structures are formed from the vaginal plate
lower vagina and hymen
what part of the female reproductive organ is innervated by ANS?
above the lover vagina
basically the upper vagina, cervix and everything above
what abnormal deformities can arise in the formation of the female reproductive organ?
lack of fusion of the paramesonephric ducts
atresia of one of the paramesonephric ducts
what does the cloaca form
urogenital sinus (bladder) anteriorly hindgut posteriorly
what does the allantois form
obliterates to form the urachus
what is the urachus
fibrous cord formed from the allantois which obliterates to form the median umbilical ligament, connecting the apex of the bladder to the umbilicus
describe what abnormalities can arise from the incomplete obliteration of the urachus
urachal fistula - pee out of umbilicus
urachal cyst along the median umbilical ligament
urachal sinus - may or may not be connected to the bladder; opens at surface of umbilicus
what does the genital tubercle form in males and in females
males - phallus which elongates
females - clitoris
what anatomical structure does not fuse in the female and forms the labia minora but does fuse in a male to enclose the penile urethra
urethral fold
what does the genital swellings form in males and in females
male - scrotal swelling –> scrotum
females - labia majora
what embryological structure remains open to from the external opening of the vagina
urogenital groove (vestibule)
the genital tubercle is larger in what gender in the early stages of development
females
the uterine canal connects on the ___ aspect of the urogenital sinus
posterior
explain the process of canalisation
sinovaginal bulbs connect the uterine canal to the posterior aspect of the urogenital sinus and the remnant membrane becomes the hymen
what is hematocolpos
blood-filled dilated vagina due to menstrual blood not being able to escape as hymen has not proliferated
the hymen is the embryological remnant of what structure
sinovaginal bulb at the point where it meets the urogenital sinus
what is a urorectal or rectovaginal fistula
incomplete separation of hindgut from urorectal septum
what is the external urethral meatus
invagination of epithelium at glans to from a urethral opening at tip of penis
what is hypospadias
abnormal urethral openings on ventral surface
what is epispadias and what other abnormality can it lead to?
urethra meatus found on dorsum of penis
genital tubercle forms in region of urorectal septum instead of cranial margin
can lead to bladder exstrophy (where bladder is exposed)
explain male and female pseudohermaphroditism
female - has ovaries but too much androgen production (congenital adrenal hyperplasia)
male - has testes but reduced androgen production or androgen insensitivity
