Fetal Embryology Flashcards
Urogenital anatomy begins to develop at what week developmentally?
~ wk 4
Development of a ______ ______, occurs first in the fetus, which forms along dorsal aspect of _____ ____ (body cavity, lined w/ ______), Posterioolateral to the vertebral region.
Urogenital Ridge
coelomic cavity
mesoderm
There are three regions of the urogenital ridge, the _____ region, a ____ region, and a ____ region
pronephric region
mesonephric region
metanephric region
At 3 wks, a _______ forms in the cervical region of embryo, which functions [very minimally] as the ______.
It then differentiates into one ___ on each side
pronephros
kidney
long nephron
By 4-4.5 wks, the embryo needs more filtration, and so the pronephros dies off by ______ as the _______ takes over, which forms in the _______ region and develops from (inferior/superior to inferior/superior).
apoptosis
mesonephros
upper thoracic-upper lumbar
Superior to inferior
The mesonephros performs filtration from _____ wks gestation, with (all/not all) parts at once
~4-10 weeks
At 4-5 wks, mesonephros filtration is replaced by the ______, which becomes the adult kidney, and part to all (depending on hormones present) of the mesonephric ducts are reabsorbed via ______.
metanephros
apoptosis
The metanephros begins to form at wk ___ and becomes functional around wks ____
5
9-10
Gonads begin to form during wks ____, which is considered the “_____ stage” because sex is not yet [genotypically/phenotypically] obvious.
5-6
indifferent; phenotypically
______ and ______ ducts are destined to be gonads
mesonephric
paramesonephric
Gonads (testes and ovaries) develop from a thickening of the ______ surface of the _______, called the gonadal ridge.
ventromedial
gonadal ridge
When and where do primordial germ cells (PGCs) differentiate?
In the neck of the yolk sac early in the 4th week
PGCs migrate to the _____ via a process called “____ ____”
genital ridge
amoeboid movement
By end of ____ wk, the PGC become incorporated into the primary sex cords/gonads via diapedesis through the _______ (otherwise known as the _____ duct), which causes the ____ to grow
6th
umbilical cord
vitelline
gonads
In developement of genital ducts __ weeks is the ____ stage
B/c Both male and female genital ducts are present
<10
Indifferent
Male duct system develops from the _____
Mesonephric ducts form ___, ___, ___, ___
mesonephric/wolffian ducts
epididymis
ductus deferens
efferent ducts
ejaculatory duct
Female duct system dev. from the ____
Paramesonephric ducts form ___, ____, ____
paramesonephric/mullerian duct
fallopian tubes
uterus
upper ⅔ of the vagina
Development of the genital ducts Begins during the ___ month of gestation or __-__ wks
From here, much depends on the presence or absence of a __ chromosome, specifically, the presence of the ___ region of the this chromosome
3rd
8-9
Y
sex-determining (SR-Y)
SR-Y codes for a protein called ___
This protein causes ___ ducts to differentiate into male genital structures, the gonads to become testes, & testes make ____→ Mullerian (paramesonephric) ducts to regress
TDF (testis determining factor)
Wolffian (mesonephric)
Mullerian Inhibiting substance
W/o an SR-Y region, there is no ___ → ___ ducts regress, gonads become ovaries, and there is no ____ → the Mullerian ducts develop into female internal genitalia
TDF
Wolffian
mullerian inhibiting substance
____ are Primary sex cords of testes containing primordial germ cells.
They are well-defined cords w/in the ___ of the testis
testes cords (spermatic cords)
medulla (middle)
The Testes cords (spermatic cords) contain two types of cells:
____, _____
Epithelial cells
Primordial germ cells
Epithelial cells become_____
Primordial germ cells become____
Sertoli cells (nurse cells for developing sperm)
Spermatoblasts
The spermatic cords remain ____ until puberty
They then ____ to form ____
solid
canalize
seminiferous tubules (ST)
Seminiferous tubules are separated from each other by ___, giving rise to____, which make ____
mesenchyme
interstitial cells (cells of Leydig)
testosterone
Fetal testes produce ___ whi
Stimulate dev. of the ____, Suppress formation of the ___
androgens
mesonephric (Wolffian) ducts
paramesonephric (Mullerian) ducts
If the testes fail to develop in the fetus, or are removed from the fetus early on, ____ will develop into female internal genitalia
If ovaries fail to develop or are removed in the female fetus, there (Is/Is no) effect on fetal sexual development
paramesonephric ducts
IS NO
A __ is a common opening shared by the digestive/reproductive/urinary tracts
Humans this develops in utero, but it becomes divided by __ of gestation
cloaca
wk 7
Cloacal separation In the indifferent stage:
___ develops at anterior end of cloacal membrane, it slongates eo form the ___
____ swellings and _____ folds appear
Genital tubercle
phallus (gonad)
Labioscrotal, Urogenital
In male external genitalia, the ___ elongates to form the penis
Elongation pulls the urogenital folds together
Folds fuse to enclose the urethra, urethral opening moves towards (end/bottom) of penis
Phallus
Bottom
Labioscrotal swellings meet ___ and fuse, forming scrotum
labioscrotal folds move inferior to the urogenital sinus and then fuse→ urogenital folds do the same
Fusion of the urogenital folds creates the ___ and the ____
posteromedially
penis, elongated urethra
____ is Incomplete fusion of urethral folds→ typically more distal
Hypospadias
Descent of the testes occurs due to the pulll from the ____ & tethers the testes in the scrotum.
Descent of the testes to the level of the internal inguinal ring occurs __ month gestation.
gubernaculum shortening
~ 7
Gonadal development occurs (Fast/Slow) in females
Until ____, the ovary cannot be identified histologically
SLOW
wk 10
___ carry the genes for ovarian development
___ genes also appear to play a role in ovarian development
X chromosomes
Autosomal
Early fetal period: Cords of ____ (sex cords) extend from surface epithelium of the developing gonad into the underlying mesenchyme (think surface area).
The ___ comes from mesodermal tissue
(pertains to ovarian development)
Sex cords ↑ in size & ____ cells are incorporated into them
___ weeks: those cords begin to break up, forming ____
Cortical tissue
Epithelium
primordial germ
~16
primordial follicles
Primordial Follicles consists of ___ & ____
Oogonium: from a primordial germ cell
Follicular Cells: from surface epithelium and surround oogonium as a layer of flattened cells
Active ___ of the oogonia occurs during fetal life, producing millions of primordial follicles ~20 wks
(No/more) oogonia form postnatally→ all are formed prior to birth
~2 million remain to become primary oocytes at time of birth; by puberty ~ ____ remain
mitosis
NO
½ million remain
In female embryos, the mesonephric ducts regress in the absence of ___
Female sexual development (does/does not) depend on the presence of ovaries or hormones→ just on the absence of MIS, which is coded for in the SR-Y region
testosterone
Does not
Both of the paramesonephric ducts pass caudally and reach the future pelvic region
They cross-over (anterior/posterior) to the mesonephric ducts to meet at the midline in the pelvic region and fuse to form a _____ in the midline
This tubular structure projects into dorsal wall of urogenital sinus, will become the____ and ____
Anterior
Y-shaped uterovaginal primordium
uterus & superior part of vagina
From where do the Fallopian tubes develop
develop from the unfused, cranial part of the paramesonephric ducts
Endometrial stroma (structural, non-glandular part of the endometrium) and myometrium are derived from a special subset of mesodermal cells called ____ (also found in heart & kidneys)
splanchnic mesenchyme
When paramesonephric ducts fuse, the process also brings together two sides of a peritoneal fold that, when folded together, form the ___.
The process also forms two peritoneal compartments: ___ and ____
broad ligament
Rectouterine pouch
Vesicouterine pouch
Enlargement at end of uterovaginal primordium induces formation of paired endodermal outgrowths called ___, which fuse to form a ___ → later, central cells of vaginal plate break down, forming the ____
sinovaginal bulbs
vaginal plate
vaginal lumen
At the most caudal part of uterovaginal canal, the sinovaginal bulbs meet w/ urogenital sinus; the urogenital sinus inverts, and moves into the pelvic cavity to meet the sinovaginal bulbs→ the 2 sets of tissue fuse and canalize, forming the _____.
vagina
The ____ is formed by invagination of the posterior wall of urogenital sinus, resulting from expansion of caudal end of the vagina
Hymen
What hormone from placenta & fetal ovaries are involved in feminization of external genitalia?
Estrogen
In females the Phallus grows but remains small, becoming the ___
clitoris
Clitoris is relatively large at 18 wks→ it develops like a penis, but the urogenital folds only fuse just posterior to the glans to form the frenulum of the ___→ the unfused parts of the urogenital folds form the ____
labia minora
labia minora
Labioscrotal folds fuse posteriorly to form the ____ and fuse anteriorly to form anterior___ and ____
posterior labial commissure
labial commissure and mons pubis
Most parts of the labioscrotal folds remain unfused and form 2 large folds of skin called ____ (homologous to the ___)
labia majora
Describe the structure of Steroids and how they are distinguished from each other , derived from cholesterol & closely related
4-ring structure of carbon atoms
by their side chains
What are steroids derived from and where are they made?
cholesterol & closely related
Ovaries
Testes
adrenal glands
What are the 3 steroid hormones
Testosterone
Estrogen
Progesterone
____ is an active steroid hormone & an important intermediary
Progesterone
_______ is Cortisol deficiency (sometimes Aldosterone) occurs, causing fetal pituitary to make more ACTH, causing cortisol to be made but much more androgen is made as well
Congenital Adrenal Hyperplasia (CAH)
90%+ of the time, CAH is due to ______ deficiency in a developing fetus
21α-hydroxylase
In Congenital Adrenal Hyperplasia (CAH) what happens to the Adrenals how does this impact the hormones being produced?
how does this impact the female and male genitalia
They enlarge because of the cortisol precursor they make
Normally, the adrenal cortex makes a small amount of testosterone→ in this case, testosterone is drastically ↑
Females appear significantly different phenotypically, males will appear the same
What is the test for CAH
check their serum and urine for elevated 17-OHP (precursor to 21a-hydroxylase)
T/F Congenital Adrenal Hyperplasia (CAH) → is an EMERGENCY
True
The genital tubercle becomes the ____ in females and the ____ in males
F = clitoral glans
M= glans penis
the Urogenital folds become the ____ in females and the ____ in males
F= vuval and labial openings
M = Phallic shaft
the scrotum in men are homologu to the ___ in females
Labia majora
the fore skin on men is homologus to the ___ and ____ in females
labia minora
clitoral hood
Estrogen controls dev.of ____ and promotes _____ development
In females, estrogen is produced by the ____
2° sex characteristics
normal bone
developing follicles of the ovaries
Estrogen variants
Estradiol (E2)
Estrone (E1)
Estriol (E3)
_____Less-active form of estrogen; created in ↓lvls in fat cells when steroids are stored there
Estrone (E1):
____ Much less active form→ created in small amounts in the liver; created in ↑ amounts in placenta; can be used as a marker for Neural Tube Defects
Estriol (E3):
____ is a Major form of estrogen made by ovaries; most hormonally-active
Estradiol (E2):
Peripheral Hormone Conversions of estrogen occur in the presence of ___
Aromatase
Only___, ___ steroid hormone can participate in enzymatic rxns
free, unbound
Estrogen target tissues include:
Brain (hypothalamic/pituitary)
CV
mammary gland
liver
reproductive tract (uterus/cervix/vagina/ovary/testes/prostate)
bone
