Embryology & Developmental Disorders Flashcards
phenotype in Mayer-Rokitansky-Kuster-Hauser syndrome
Normal secondary sex characteristics
Normal Tanner stage
Agenesis or incomplete uterus, vagina, or both
karyotype in Mayer-Rokitansky-Kuster-Hauser syndrome
46XX
when does organogenesis occur
wks 3-8
other name for Wolfian duct
mesonephric duct
other name for Mullerian duct
paramesonephric duct
ureteral bud turns into
ureters, renal pelvis, and calycesme
metanephric mass becomes
functional nephrons
what drains into the cloaca
ureteric bud and mesonephric duct
what is the cloaca
the termination of the urogenital and GI tracts
where does the cloaca come from
the allantois
what is the allantois
diverticulum of the yolk sac past the caudal end of the embryo
what is the cloaca divided into
urorectal septum divides it into urogenital sinus and anorectal canal
what does urogenital sinus become
bladder, urethra, vagina
what does the allantois become
urachus > median umbilical ligament
when does gonadal development start
5 wks
when are there 100K egg/sperm cells
6wks gestational (germ cells)
what are gonads derived from
Coelomic (germinal) epithelium
Underlying mesenchyme
Primordial germ cells
where to germ cells originate
wall of the yolk sac
What do primary sex cords become
seminiferous tubules in males,
vestiges in females
when is undifferentiated gonad complete
by 7th week
what are the two genital tracts
2 Wolfian (mesonephric) ducts
2 mullerian (paramesonephric ducts)
where do paramesonephric ducts come from
From invagination of coelomic epithelium on lateral aspect of mesonephros.
Bud hollows to form an open duct
what gene determines gonad differentiation
SRY gene on Y chromosone (sex-determining region Y) that codes for TDF (testis determining factor)
when does gonad differentiation occur
testis at 4-6wks if TDF present
ovary at 6-8wks if TDF absent
when do you have max number of germ cells in life
20wks development (22wga) have 6-7 million
when do primordial follicles form
16-20wks development (18-22wga)
components of primordial follicle
1o oocyte arrested in prophase of first meiotic division
Single layer of follicular cells (from sex cord) – Pre-granulosa cells
Loose outer layer of mesenchyme – Pre-theca cells
how many oocytes at birth
1-2million
how many oocytes at puberty
300K
what drives differentiation of mullerian ducts
Mullerian inhibiting factor
when does differentiation of mullerian ducts occur
8wks
what does mullerian duct become
if no MIF by 8wks, fuse to form uterovaginal canal > becomes uterus and upper part of vagina
upper part of mullerian duct becomes
epithelium and glands of endomterium
where does endometrial stroma and myometrium come from
surrounding mesenchymal girdle
unfused segments of mullerian ducts become
fallopian tube with fimbriae
cyst of morgagni is remnant of
mullerian duct (part that didn’t get incorporated into tube)
caudal inguinal ligament becomes
uteroovarian and round ligaments
cranial inguinal ligament becomes
IP
what cretes the borad ligament
urogenital mesentery meet as a result of fusion of the Mullerian ducts
where do gartner’s ducts come from
regression of Wolfian ducts in absence of androgens
interruption of mullerian duct fusion can result in:
Uterus didelphys
Bicornuate uterus
Arcuate uterus
If midline septum fails to degenerate, leads to
septate uterus
If one Mullerian duct fails to form or becomes atretic, leads to
unicornuate uterus or bicornuate uterus with rudimentary horn
how is vagina formed
upper 1/3 mullerian ducts (canalized)
lower 2/3 urogenital sinus
imperforate hymen caused by
failure of resorption of hymen
failure of canalization of vagina
what results from incomplete canalization
double vagina
what causes formation of testis
Testes determining factor (TDF) produced from SRY gene
composition of sex cords
spermatogonia
supporting cellsw
what produces mullerian inhibiting factor (MIF)
supporting cells (Sertoli)
epididymis comes from
Upper Wolfian duct adjacent to testis becomes elongated and convoluted
ductus deferens comes from
Remainder of Wolfian duct developes a thick muscular coat
what becomes penis or clitoris
genital tubercle
what androgen is needed to form male genitalia
DHT (dihydrotestosterone)
5-a reductase (enzyme) turns testosterone into DHT
5-a reductase deficiency can lead to
- unable to produce DHT
- External genitalia will be female (depends on DHT) - Blind vaginal pouch
- Internal genitalia will be male (depends on testosterone)
- At puberty, external genitalia sensitive to testosterone so they’ll have virilization
analogy of skene glands in men
prostate gland
when does external genitalia differentiation occur
end of 3rd month
female remnant of gubernaculum
round ligament & uteroovarian ligaments
what is processus vaginalis
when peritoneum invaginates, it follows gubernaculum and enters scrotum creating processus vaginalis
– forms inguinal canal
what is hydrocele
fluid trapped inside processus vaginalis
if processus vaginalis remains patent
- congenital inguinal hernia
- normally obliterates
near birth
what induces wolffian duct development
testosterone
umbilical cord comes from
body stalk
erm cells come from
yolk sac
umbilical vessels come from
allantois
urinary bladder comes from
urogenital sinus
gartner’s duct comes from
wolffian (mesonephric) duct
