Embryology Quiz 1 - Week 2/3
Questions Fully Solved.
What germ layers does the embryoblast split into? - Answer epiblast and hypoblast
What layers does the trophoblast split into? - Answer inner cytotrophoblast and outer
syncytiotrophoblast
What is the blastocyst cavity is remodeled twice into? - Answer primary and secondary yolk
sacs
What is the extraembryonic mesoderm split into? - Answer parietal and visceral layers
What are the 3 landmark events of week 3? - Answer 1. appearance of the primitive streak -
> epiblast layers : establishment of embryo orientation
2.development of notochord and beginning of nervous system development
3. gastrulation: formation of 3 germ layers
What does the hypoblast form? - Answer 1) yolk sac
2) fetal side of the placenta
What is the space in the epiblast called? - Answer primitive amniotic cavity
What do the amnioblast cells (from the epiblast) and the other epiblast cells form? - Answer
amnioblast cells -> top of the amniotic cavity
epiblast cells -> floor of the amniotic cavity
What does the hypoblast cells form? - Answer these cells forced inferiorlaterally and forms
an inner lining (exocoelomic/ Heuser's membrane)
to remodel the blastocystic cavity into the primary yolk sac
What is the blastocystic cavity remodeled into? - Answer primary yolk sac
, What is exocoelomic/ Heuser's membrane? - Answer an inner blastocyst lining that models
the blastocystic cavity
What do hypoblast cells form? - Answer form the primitive and secondary/definitive yolk sac
What does the outer cell mass differentiate into? - Answer trophoblast differentiates into:
inner cell mass: cytotrophoblast (yellow) - surrounds the blastocyst, primary yolk sac, and
amniotic cavity
outer cell mass: syncytiotrophoblast (red) - partially surrounds cytotrophoblast
What type of cells are cytotrophoblast cells?
What happens when cytotrophoblast divide? - Answer Cytotrophoblast are mitotically active
and divide and these cells then migrate into the syncytiotrophoblast layer where they fuse and
lose their individual cell membranes
Day 8 of blastocystic development: trophoblast layers
what is the function Syncytiotrophoblast? - Answer Syncytiotrophoblast (STB) invade
maternal endometrium and
-continually erode enlarged endometrial spiral blood vessels and uterine glands for nutrition
Day 8 of blastocystic development: trophoblast layers
what is the function Cytotrophoblast? - Answer Cytotrophoblast will divide and forms local
swellings (*-primary chorionic villi) that bulge into the surrounding syncytiotrophoblast (STB) to
increase surface area of CTB (uteroplacental circulation)
What do syncytiotrophoblast form when it continues to erode the endometrial lining/blood
vessels and form holes - what's the name? (holes in syncytoptrphoblasts) - Answer it forming
lacunae
What do lacunae in the syncytotrophoblast fill up with? - Answer Blood vessels of
endometrium fill these lacunae with:
1)oxygenated blood and
2) uterine glandular secretions for additional blastocyst nutrition via diffusion
Questions Fully Solved.
What germ layers does the embryoblast split into? - Answer epiblast and hypoblast
What layers does the trophoblast split into? - Answer inner cytotrophoblast and outer
syncytiotrophoblast
What is the blastocyst cavity is remodeled twice into? - Answer primary and secondary yolk
sacs
What is the extraembryonic mesoderm split into? - Answer parietal and visceral layers
What are the 3 landmark events of week 3? - Answer 1. appearance of the primitive streak -
> epiblast layers : establishment of embryo orientation
2.development of notochord and beginning of nervous system development
3. gastrulation: formation of 3 germ layers
What does the hypoblast form? - Answer 1) yolk sac
2) fetal side of the placenta
What is the space in the epiblast called? - Answer primitive amniotic cavity
What do the amnioblast cells (from the epiblast) and the other epiblast cells form? - Answer
amnioblast cells -> top of the amniotic cavity
epiblast cells -> floor of the amniotic cavity
What does the hypoblast cells form? - Answer these cells forced inferiorlaterally and forms
an inner lining (exocoelomic/ Heuser's membrane)
to remodel the blastocystic cavity into the primary yolk sac
What is the blastocystic cavity remodeled into? - Answer primary yolk sac
, What is exocoelomic/ Heuser's membrane? - Answer an inner blastocyst lining that models
the blastocystic cavity
What do hypoblast cells form? - Answer form the primitive and secondary/definitive yolk sac
What does the outer cell mass differentiate into? - Answer trophoblast differentiates into:
inner cell mass: cytotrophoblast (yellow) - surrounds the blastocyst, primary yolk sac, and
amniotic cavity
outer cell mass: syncytiotrophoblast (red) - partially surrounds cytotrophoblast
What type of cells are cytotrophoblast cells?
What happens when cytotrophoblast divide? - Answer Cytotrophoblast are mitotically active
and divide and these cells then migrate into the syncytiotrophoblast layer where they fuse and
lose their individual cell membranes
Day 8 of blastocystic development: trophoblast layers
what is the function Syncytiotrophoblast? - Answer Syncytiotrophoblast (STB) invade
maternal endometrium and
-continually erode enlarged endometrial spiral blood vessels and uterine glands for nutrition
Day 8 of blastocystic development: trophoblast layers
what is the function Cytotrophoblast? - Answer Cytotrophoblast will divide and forms local
swellings (*-primary chorionic villi) that bulge into the surrounding syncytiotrophoblast (STB) to
increase surface area of CTB (uteroplacental circulation)
What do syncytiotrophoblast form when it continues to erode the endometrial lining/blood
vessels and form holes - what's the name? (holes in syncytoptrphoblasts) - Answer it forming
lacunae
What do lacunae in the syncytotrophoblast fill up with? - Answer Blood vessels of
endometrium fill these lacunae with:
1)oxygenated blood and
2) uterine glandular secretions for additional blastocyst nutrition via diffusion
