Repro- Embryology Flashcards
What is embryogenesis
the first 8 weeks of embyro development after fertilisation
day 5 - blastocyte
week 2-3 - bilaminar disc
week 3-4 - trilaminar (3 germ layers)
week 5-8 - organoenesis
When does the fertilised egg form a blastocyst?
day 5
How is the blastocyst organised?
Two cell groups
- inner cell mass - embyroblast (develop to form baby)
- trophoblast (develops to form the placenta)
What does the inner cell mass of the blastocyst become?
Bilaminar disc (columnar epithelial cells - epiblast) and hypoblast cells
What are the two layers of the bilaminar disc called?
Epiblast -> (becomes 3 germ layers after gastrulation)
Hypoblast -> (becomes extraembryonic mesoderm)
cytotrophoblasts (outer cells of trophoblast) for what?
Chorionic villi (invades endometrium during implantation)
The inner cell mass of blastocyst differientiates into the bilaminar disc
a. true
b. false
a. true
- epiblasts
- hypoblasts
Two cavities form either side of the bilaminar disc, what are they called?
cytotrophoblasts/syncytiotrophoblasts cells (form placenta)
Epiblast cells
Hypoblast cells
——————
Yok Sac
the inner cell mass of blastocyt forms the bilaminar disc
a. true
b. false
a. true
what do epiblast cells differieniate into?
3 germ layers via gastrulation (trilaminar disc)
(begins with primitive streak appearing in the caudal end of the epiblast).
through this streak, cells migrate to form the
1. endoderm (displace hypoblasts)
2. mesoderm
3. remaining epiblast cells (ectoderm) do not migrate
Ectoderm forms?
CNS, PNS, neuroendocrine organs , (adrenal medulla, pituitary gland)
Which part of the mesoderm form the kidneys, utreter and gonads?
intermediate mesoderm
How are diyzgotic twins formed?
two or more eggs are fertilised
and implanted
non-identical - genetically distinct
more common
How are monozygotic twins formed?
1 embyro is split!!
identical twins
splitting of embryo determines nature of the pregnancy
What does dichorionic diamniotic mean?
how does it occur
have a seperate placenta and seperate amniotic sac
THE EARLY EMBRYO SPLITS before implanting in the womb
20% of monozygotic twins
What does monochorionic diamniotic mean?
how does it occur?
Share placenta and have seperate amniotic sac
Early embyro implants in the womb and then splits
75% of monozygotic twins
What does monochorionic monoamniotic sacs?
Share placenta and share amniotic sac
Early embyro implants in the womb and then splits LATER ON (the later splits after implantation - the more likely to share both)
5% of monozygotic twins - BOTH are shared - high risk
The inner cell mass of the blastocyst called the embyroblast goes through differientation into a bilaminar disc followed by a trilaminar disc through a process callled?
gastrulation
beyond 8 weeks the embyronic period ends and the fetal period begins
a.true
b. false
a. true
embyrogenesis is the 1st eight weeks of embyro development post fertilisation
Reproductive and renal systems have a common origin and develop from the ?
intermediate mesoderm
The intermediate mesoderm develops into
urogenital ridge
which develops into
- nephrogenic cord (laterally)-> kidney/ureters
- gonadal ridge (medially)-> gonads
Horseshoe kidney
fused kidney
duplex kidney
two kidneys at one side
pelvic kidney
kidney not ascended from pelvis during development
The caudal end of the yok sac develops into
the cloaca
the cloaca is divided by the urorectal septum to form
- urogential sinus -> bladder/urethra
- anal canal -> rectum and hindgut
What region of the Y chromosome determines sex
SRY gene (SYR gene produces testes determining factor - SRY protein)
SRY protein produces the testis
protein acts on indifferent gonad to promote the formation of the testes
cryptorchidism
undescended testicle
what develops from the nephrogenic cord
kidney and ureter
what develops from the urogenital part of the cloaca
bladder and urethra
urinary system and gonads have a common origin?
urogenital ridge of the intermediate mesoderm
gonads develop from the gonadal ridge
a. true
b. false
a. true
Differientiation into testis or ovary is dictated by the presence of Y chromosome and AMH
a. true
b. false
a. True
Anti-Mullerian hormone - The AMH gene provides instructions for making a protein that is involved in male sex differentiation.
During development of male fetuses, the AMH protein is produced and released (secreted) by cells of the testes.
There are two sets of genital ducts? which are undifferentiated in the embyro
- mesonephric duct
- paramesonephric duct (female duct development)
in men - AMH causes Mesonephric to continue to develop (M for Men)
the mesonephric duct forms the epididymis , vas deferns and seminal vesicles in men
a. true
b. false
a. true
under effect of testosterone
in women the paramesonephric duct continues to develop and the mesonephric duct regresses
a. true
b. false
a. true
in the absence of AMH
ducts grow medially and fuse -> canalise to form uterus and upper 2/3 vagina
urogential folds form what in
- male
- female
- spongy urethra in men
- labia minora
genital tubercle forms what in
- female
- male
1.clitorus 2. penis
labioscrotal swelling forms what in
1. men 2. women
- scrotum 2. labia majora
what causes a micro-penis?
genital tubercle does not elongate fully
crytochordism
undescended testicle
absence of the vas deferens is common in what disease?
cystic fibrosis
if the paramesonephric duct doesnt develop - there will be uterine agenesis
a. true
b. false
a. true
underdevelopment or absence uterus
why might uterine not develop
- paramesonephric ducts dont develop or are underdeveloped
- ducts do not fuse in the middle
- ducts fuse but do not undergo cannalisation (stay as band instead)
a rare congenital condition where the hymen membrane doesn’t develop properly in the fetus, blocking the vaginal opening
imperforate hymen
AMH in males causes the paramesonephric ducts to regress
a. true
b. false
a. true
In males, paramesonephric duct develops under the effect of testosterone to form the epididymis, vas deferens and seminal vesicles
a. true
b. false
b. false
the mesonephric duct!! - wolffian
In females, the paramesonephric duct fuse to form the uterus, upper 2/3 vagina
a. true
b. false
a. true
lower 2/3 vagina is formed from the urogenital sinus
What 3 structures form the male and female external genitilia
- genital tubercle
- urogenital folds
- labioscrotal swelling
Reproductive tract abnormalities are associted with renal abnormalities
a. true
b. false
a. true
they can be due to common origin of intermediate mesoderm
