Embryology week 15 Flashcards
When does implantation of Blastocyst occur
- 6 to 10 days after fertilization
As the blastocyst implants (at the start) what happens to the trophoblasts
Trophoblast differentiate into 2 layers :
- Cytotrophoblasts - Inner layer
- syncytiotrophoblasts- outer layer
What happens in the second step ( Completion of implanation of blastocyst) starting with syncytiotrophoblasts
-Syncytiotrophoblast erodes endometrial tissue then the blastocyst become embedded in the endometrium
-Endometrial cells undergo apoptosis, aiding implantation.
Explain what happens in the completion of Implantation of Blastocyst after the blastocyst is embedded in the endometrium
-Syncytiotrophoblast produces human chorionic gonadotropin (hCG).
-hCG maintains the corpus luteum, which secretes estrogen and progesterone to sustain pregnancy.
- By the end of the second week enough hCG is produced for a positive pregnancy test
Name the 8 molecules that regulate implantation of the blastocyst
- Microvilli
-Integrins
-Cytokines
-Prostaglandins
-hCG
-progesterone
-growth factors
-enzymes
How is the Amniotic cavity formed
- A small space appears in the embryoblast, becoming the amniotic cavity
- Amnioblasts spereate from the epiblast to form the amnion,which encloses the amniotic cavoty
How is the embryonic disc formed
- The embryoblast changes into a bilaminar embryonic disc with two layers:
- Epiblast
- Hypoblast
-How is the Primary Umbilical vesicle formed
-What develops around the umbilical vessicle and amnion
- The hypoblast and exocoelomic membranes form the primary umbilical vesicle
- Extraembryonic mesoderm
Where is lacunae formed
Syncytiotrophoblasts
What is lacuneae
small spaces
What does the lacunea fill with, and what does that form
- maternal blood and cellular debris
- forming embryotroph for nutrition
How are decidual cells formed ?
- Endometrial connectove tissue cells accumulate glycogen and lipids, becoming decidual cells
What is the function of decidual cells
- Provide nutrition and immune protection for the embryo
How are lacunar networks formed
- lacunae fuse to form lacunae networks
How is the Extraembryonic Coelom and secondary Umbilical vesicle formed
The Extraembryonic coelomic spaces merge to form the Extraembryonic coelom, surrounding the amnion and umbilical vesicle.
The primary umbilical vesicle shrinks, while a secondary umbilical vesicle forms
Describe characteristics of the umbilical vesicle
- Contains no yolk but plays a role in nutrient transfer
- where primordial germ cells origin
Where does implantation sites occur
In the uterine endometrium in the superior part of the uterus
Where is implantation more common the posterior or anterior wall
Posterior wall
How can implantation be detected
Using ultrasonography
hCG radioimmunoassays can detect implantation
Name the stages in forming the Chorionic Sac
- Formation of the Primary Chorionic Villi
- Splitting of the Extrembryonic Mesoderm
-Formation of the Chorion and Chorionic Sac
Explain the formation step of the primary Chorionic Villi:
- What it is induced by
- What the villi forms
- Growth is induced by the extrambryonic somatic mesoderm
- Forms columns with the syncytial coverings
Explain what happens in the splitting of the Extraembryonic Mesoderm and each function (2nd step of chorionic sac development)
Splist into 2 :
-Extraembryonic somatic mesoderm: Lines the trophoblast and covers the amnion.
-Extraembryonic splanchnic mesoderm: Surrounds the umbilical vesicle
Explain what happens in the formation of the chorion and chorionic sac:
-Chorion is formed by :
-Extraembryonic somatic mesoderm
- Two layers of trophoblasts
What does the chorionic sac contain
- Embryo, amniotic sac, umbilical vesicle
