Chapter 3 Part 2 Flashcards
What happens when the morula enters the uterine cavity?
Fluid starts penetrating through the zona pellucida into the intercellular spaces of the inner cell mass.
What is formed as the intercellular spaces become confluent in the inner cell mass?
A single cavity known as the blastocyst.
What are the two parts of the blastocyst, and where are they located?
The embryoblast (inner cell mass) is at one pole, and the trophoblast (outer cell mass) forms the epithelial wall of the blastocyst
When does the zona pellucida disappear?
The zona pellucida disappears to allow implantation to begin.
How do trophoblastic cells initiate attachment during implantation?
Trophoblastic cells express L-selectin, which binds to carbohydrate receptors on uterine epithelium.
What is the role of selectins in implantation?
Selectins mediate the initial attachment of the blastocyst to the uterine epithelium.
What molecules are involved in further attachment and invasion after initial attachment?
Integrins on the trophoblast interact with extracellular matrix molecules like laminin and fibronectin.
What is the role of integrins in attachment and invasion?
Integrins expressed by the trophoblast interact with extracellular matrix molecules to promote attachment and migration.
How do integrin receptors for laminin and fibronectin differ in function?
Integrin receptors for laminin promote attachment, while those for fibronectin stimulate migration.
How do trophoblast and endometrial actions contribute to implantation?
Trophoblast and endometrial actions interact along signal transduction pathways to regulate trophoblast differentiation, resulting in implantation.
When does the human zygote begin implantation?
By the end of the first week of development, after passing through the morula and blastocyst stages.
What is the embryonic structure at one pole of the blastocyst called?
The embryoblast, which was previously known as the inner cell mass.
What is the function of trophoblastic cells during implantation?
Trophoblastic cells initiate attachment and invasion, facilitating the implantation process.
What is the initial attachment process of the blastocyst called?
The initial attachment process is mediated by the interaction between L-selectin on trophoblast cells and carbohydrate receptors on the uterine epithelium.
What molecules are involved in the attachment and migration of the trophoblast?
Integrins, laminin, and fibronectin play roles in trophoblast attachment and migration during implantation.
What influences embryoblast cell differentiation at the early blastocyst stage?
Fibroblast growth factors (FGFs) influence embryoblast cell differentiation.
What are the two types of cells that embryoblast differentiates into under FGF influence?
Epiblast and hypoblast cells
How do epiblast and hypoblast cells initially appear in the embryoblast?
They are scattered throughout the embryoblast
What happens to epiblast and hypoblast cells near the time of implantation?
They segregate based on their specification, forming a dorsal layer of epiblast cells and a ventral layer of hypoblast cells adjacent to the blastocyst cavity
How is dorsal-ventral polarity established in the embryo?
Dorsal-ventral polarity is established by the segregation of epiblast and hypoblast cells into distinct layers.
What is the role of some hypoblast cells in the embryo?
Some hypoblast cells are specified to form the anterior Visceral endoderm (AVE).
Where do AVE cells migrate, and what is their function?
AVE cells migrate to the cranial end of the embryo and secrete nodal antagonists, including cerberus and lefty, to specify the cranial end of the embryo
How is the cranial-caudal embryonic axis established, and when does it occur?
The cranial-caudal embryonic axis is established near the time of implantation (days 5.5 to 6) through the interaction of AVE cells secreting nodal antagonists to specify the cranial end, while nodal promotes the primitive streak formation at the caudal end.
Three layers of the uterine wall
Endometrium
Myometrium
Perimetrium
