Bilaminar Embryo And Implantation Flashcards
What do receptors outside the trophoblast cells allow for?
Adherence to the uterine wall
What does the inner cell mass differentiate into?
Two cell populations - epiblast and hypoblast
What do trophoblasts split into?
Cytotrophoblasts and Syncytiotrophoblasts
Where do cytotrophoblasts proliferate?
At the embryonic region
What is a syncytium?
A group of cells that have lost their cell membrane and come together.
Why does the syncytium have no cell membrane?
So it can make its way through the endometrial epithelium without causing damage
What facilitates the Syncytiotrophoblasts?
The matrix metalloproteinases (MMP) secreted by the embryo
What does the syncytiotrophoblast produce?
Human chorionic gonadotropin
What happens to the epiblast mid-implantation?
The cell mass begins to flatten and fluid collects at the centre. Amniotic cavity forms.
What is the function of human chorionic gonadotropin?
It feeds back to he corpus luteum and creates a feedback loop to maintain progesterone levels
Why do progesterone levels need to be maintained?
To maintain the endometrium in a vascularised and thickened state
When do the Syncytiotrophoblasts fully envelope the embryo?
When the embryo is fully implanted
How is the primitive yolk sac created?
By hypoblast proliferation. The cells move round the edges of the blastocystic cavity to create a new cavity.
What produces the Extraembryonic mesoderm?
The yolk sac and cytotrophoblast cells
What cell types invade the maternal blood vessels following implantation?
Syncytiotrophoblasts
What fills the synosoid after implantation?
Maternal blood and the breakdown of maternal connective tissue
When does the definitive yolk sac develop?
AT days 12-14
When does the second wave of hypoblast proliferation occur?
Day 12-14
How are exocoelemic cysts produced?
By the movement of the excess primitive yolk sac to the abembryonic pole
What has occurred by the end of week 2?
Full implantation
Inner cell mass formed the Bilaminar germ disc
3 foetal membranes formed
Secondary yolk sac formed
Chorion formed
Connecting stalk will become umbilical cord
What is the function of the amniotic fluid?
Suspends the foetus in fluid
Allows symmetrical development
Allows movement
Protects from trauma
Prevents perforation of the amniotic sac
What is within amniotic fluid?
Electrolytes, proteins, gene material, carbs, lipids, urea
Where does amniotic fluid come from?
Amniotic epithelium, filtration from maternal and foetal vessels, foetal urine and lung secretions
What is oligohyraminos and what are its potential causes?
A decreased amount of amniotic fluid caused by under secretion from the foetus and lack of production by the mother
