Embryology of the Gonads Flashcards
what is the genetic sex determined by
sperm
what is the SRY
sex-determining region of the Y chromosome
it is a gene which initiates the production of testis determine factor
what happens if there is no chromosome Y in sperm
no Y = no TDF - female development commences
what is the reproductive and urinary system derived from
intermediate mesoderm
urogenital ridge
then into the two separate systems
what weeks do the male and female gonads differentiate
weeks 5-6
what specifically forms the primitive sex cords
epithelium covering the urogenital ridge proliferates and penetrates the underlying mesoderm
what happens in week six in forming the genitalia
primordial cells migrate to genital ridge
what does the indifferent gonad be split into
outer cortex and inner medulla
what is the fate of medullary and cortical region dependant on
TDF production
what are the difference in structures of developing male and female gonads
cortical cords
medullary cords
tunica albuginea
cc - develop in female but none in male
mc - develop in males but regress in females
ta - develop in males, no development tin females
what do the medullary cords in the testis turn into
rete testis (hilum) seminiferous tubules
what is the tunica albuginea
in the 4th month it is a connective tissue that develops around the testes
what happens to development of the ovary between 7th week and 5th month
medullary cords degenerate
surface epithelium continues to proliferate and produces second generation cords - cortical cords
cortical cords split and surround oocytes
all oocytes are present at birth
at what week is the male and female gonad distinguishable
week 7
describe the start of the descent of the testes from the posterior abdominal wall in weeks 7-12
extrabdominal gubernaculum shortens pulling testis towards the anterior abdominal wall where they arrive at the internal inguinal ring from 3rd to 7th month
what happens after 7 months of pregnancy to the descent of the testes
gubernaculum shortens again pulling them through inguinal canal of abdominal wall - aided by pressure of growing organs
testes reach scrotum by 9th month just before birth
what happens within the first year of fetal growth to the processes vaginalis
obliterates leaving a remnant round the testes known as the tunica vaginalis
what are the 3 muscles of the inguinal wall
transverses abdominus (and fascia ) internal / external oblique
what is the deep and superficial ring of the lingual canal
deep - entrance of inguinal canal and is located in transversals fascia
superficial - exit of inguinal canal and is located in external oblique
what are the coverings of the testes and where are they from
internally
internal spermatic fascia - from transversalis fascia
cremasteric fascia - from internal oblique muscle
external spermatic fasica - from external oblique muscle
what is a patent processes vaginalis and what are the clinical consequences
parts of the processes vaginalis may remain unfused leaving small cyst
cysts can produce fluid and swell - hydrocele
can be surgically removed
if the processes vaginalis remains open to abdominal cavity intestines may protrude through inguinal canal - indirect inguinal hernia
what is transillumination in hydrocele
formed by clear fluid and therefore light can pass through it
if it were a hernia aor tumour light would be blocked by it
what is cryptorchidism
affects 1-4% broths but most correct themselves at 3 months of age
undescended testicles - can be surgically corrected at 4-6 months
what is cryptorchidism associated with
increased risk of testicular cancer and infertility
describe the descent of the ovaries
descend to pelvic brim
gubernaculum passes through inguinal canal and inserts onto labia majora
persists in adult as the ovarian ligament proper and the round ligament of the uterus
what is the development of the male genital ducts driven by
SRY gene
what does the SRY gene encode
testis determining factor
how do sertoli cells from
somatic support cells invest PGC’s with SRY gene and differentiate into sertoli cells
what do sertoli cells do
secrete anti-mullerian hormone (AMH) - which causes degeneration of paramesonephric
what do sertoli cells cause differentiation of
mesoderm of the gonad into leading cells
what do leydig cells do
produce testosterone which promote maintenance and further development of the mesonephric ducts
what does the mesonphrenic duct develop into
efferent ductules
epididymis
vas deferent
seminal vesicle
parts of the paramesenophenic duct persist as what
appendix testis
utriculus prostaticus
what happens in the absence of SRY
development of the genital ducts - no anti-mullerian hormone - paramesophric ducts remain
no testosterone - mesonephric ducts degenerate
what do the three parts of the paramesonphric duct in females turn into
cranial and horizontal parts which become the uterine tubes
caudal parts fuse to from uterine canal
what remnants of the uterine duct persist
check photos
epophoron
paraophoron
gartners cyst
what does the cloaca in women divide into
urogenital sinus and anus
how does the vagina form
urogenital sinus develops sinovaginal bulbs that fuse with caudal tips of paramesonphric ducts to from vagina
what are 3 common abnormalities of the uterus
failure of paramesonphric ducts to fuse
failure of uterine septum to degenerate
failure of one paramesonephirc duct to elongate
what percentage of woman have an abnormal uterus and what are the clinal consequences
1% of population - higher risk of miscarriage, premature delivery or dystocia (difficult birth)
describe persistent mullein duct syndrome
affects genetic males
mutation in AMH gene
no AMH production so parameonephric ducts persist so both mesonephric and paramesonephric duct derivatives develop
normal male external genitalia but associated with crytorchodisim
what are the indifferent stages of external genitalia development
mesoderm cells migrate surrounding cloacal membrane forming elevated cloacal folds
these unite to anteriorly to from genital tubercle ie either future penis or clitoris
cloacal folds divide into anal and urethral division
genital swellings appear next to urethral folds - which are future scrotum or labia
what is the development of male external genitalia dependant on
androgens
what does the genital tubercle elongate to form
phallus
which direction do genital swellings enlarge and move towards
caudally
describe the formation of the penal urethra
Urethral folds pulled forward and form lateral walls of the urethral groove
Urethral groove is lined by epithelium and form urethral plate
End of 3rd month - urethral folds close over urethral plate to form penile urethra
what is hypospadia
incomplete fusion of urethral folds - urethra opens on ventral surface of penis
occurs in 3-5 out of 1000 births
difficulty urinating
can be repaired surgically using forsaken
what is epispadia
usually result of urethra oping on the dorsal surface of the penis
1 in 30,000
results from the improper location of the genital tubercle posterior to urogenital sinus - urethral groove located on dorsal surface of the penis
what is episadia commonly associated with
extrophy of the bladder
what is the development of the external female genitalia dependant on
estrogens
describe the formation of the external female genitalia
Genital tubercle elongates slightly to form clitoris
Urethral folds do NOT fuse - form labia minora
Genital swellings form labia majora
Urogenital groove remains open
when can you start to tell the difference in fallus from male and female
from the 13th week
they are too similar for the first 12 weeks
