L18. Early Development 2 Flashcards
What does the syncytiotrophoblast do?
- produce hCG ( stop menstruration by keeping estrogen and progesterone high)
- produce proteolytic enzymes that digests and invade the endometrium and surround the blastocyst
- forms trophoblastic lacuna (gaps that allow maternal blood to flow through)
What are the 2 layers that grow around the amnionic cavity?
- epiblasts
2. amnioblast
What forms the Heuser membrane?
hypoblast cells that start to migrate
What surrounds the primary yolk sac/
- Heuser membrane
2. Hypoblast
What is the extraembryonic mesoderm?
- extraembryonic reticulum is invaded by the epiblasts cells
- extraembryonic mesoderm lines along the Heuser’s membrane and the cytotrophoblast
- separates the cytitrophoblasts from the amnioblast
What is the chronic cavity?
Forms between the 2 layers of mesoderm as fluid fills in the gaps
What happens on day 13 of implantation?
- Heuser’s membrane and connected extraembryonic mesoderm elongates and buckles
- definitive yolk sac forms as remnants of the primary yolk sac
What are the characteristics at the start of gastrulation?
- syncitiotrophoblasts have started to establish the placenta
- amniotic cavity forms
- definitive yolk sac forms
- embyo proper is formed
- has 2 layers; hypoblast and epiblast
How does the placenta form?
The extraembryonic mesoderm digs deeper into the synciyotrophoblast and thus it pushes down the cytotrophoblast
What are the 2 contributing components to the placenta?
- maternal component: decidua basalis
2. fetal component: chorionic villi
What is the function of the placenta?
allows gas, nutrients and waste exchange.
blood comes close to one another but do not contact.
What are the 4 barriers between the mother’s and fetuses blood?
- synctiotrophoblast
- cytotrophoblast
- connective tissue surrounding the blood vessel
- epithelial of the blood vessel
What is the function of the amnion?
protects the embryo, eliminates waste
What is the function of the yolk sac?
produces blood until the liver forms
germ cells form here
migrate to gonads
What is gastrulation?
rearrangement of cells into the primary germ layers (mesoderm, endoderm and ectoderm)
Identify all the components on page 3 part 2
page 3 part 2