Fetal Membranes and Placenta Development

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Questions and Answers

What is the source of the fetal component of the placenta?

Maternal endothelial cells

Spiral arteries in the uterus

Trophoblast and extraembryonic mesoderm (correct)

Uterine endometrium

What is the role of cytotrophoblast cells in the erosion of maternal vessels?

To form well-developed villi at the embryonic pole

To invade spiral arteries and replace maternal endothelial cells (correct)

To create hybrid vessels containing both fetal and maternal cells

To release blood into intervillous spaces

What process do cytotrophoblast cells undergo to accomplish the invasion of spiral arteries?

Erosion of maternal vessels

Endovascular invasion

Maternal blood delivery

Epithelial-to-endothelial transition (correct)

Where is maternal blood delivered to the placenta from?

Spiral arteries in the uterus Signup and view all the answers

What are the villi like at the embryonic pole and abembryonic pole during the beginning of the second month of development?

Well formed at the embryonic pole and poorly developed at the abembryonic pole Signup and view all the answers

What creates hybrid vessels containing both fetal and maternal cells in the placenta?

Endovascular invasion by cytotrophoblast cells Signup and view all the answers

What is the function of the cytotrophoblast cells in the placenta?

They transform the spiral arteries into low-resistance vessels Signup and view all the answers

What is the role of the decidua basalis in the placenta?

It forms the maternal portion of the placenta Signup and view all the answers

What happens to the villi on the embryonic pole as pregnancy advances?

They continue to grow and expand Signup and view all the answers

What is the structure that makes up the placenta and participates in the exchange process?

Chorion frondosum Signup and view all the answers

What happens when fusion of the amnion and chorion occurs?

The uterine lumen is obilterated Signup and view all the answers

What characterizes the junctional zone between the fetal and maternal portions of the placenta?

Presence of amorphous extracellular material Signup and view all the answers

What is the fate of most cytotrophoblast cells by the beginning of the fourth month?

They degenerate and disappear Signup and view all the answers

Which layer separates the maternal and fetal circulations by the beginning of the fourth month?

Syncytium and endothelial wall of blood vessels Signup and view all the answers

What happens to newly formed free villi by the beginning of the fourth month?

Cytotrophoblastic cells disappear and they become primitive Signup and view all the answers

What is the role of intervillous spaces within the placenta?

To be filled with maternal blood for exchange purposes Signup and view all the answers

What characterizes the structure of decidua over the chorion frondosum?

Consists of a compact layer of large decidual cells with abundant lipids and glycogen Signup and view all the answers

How does fusion of amnion and chorion affect the chorionic cavity?

It becomes stretched and degenerates Signup and view all the answers

Study Notes

Placenta Development and Function

The fetal component of the placenta originates from the trophoblast, specifically from the cytotrophoblast and syncytiotrophoblast layers.
Cytotrophoblast cells play a crucial role in eroding maternal blood vessels to facilitate nutrient exchange; they invade maternal tissues, remodeling blood flow.
Cytotrophoblast cells undergo a process called epithelial-to-mesenchymal transition (EMT) that allows them to invade spiral arteries during implantation.
Maternal blood reaches the placenta via spiral arteries, which deliver blood rich in nutrients and oxygen to support fetal development.
At the beginning of the second month of development, villi at the embryonic pole are more developed and branching, while those at the abembryonic pole are shorter and not as extensive.

Vascular Integration and Functionality

Hybrid vessels, containing both fetal and maternal cells, are created through the invasion of cytotrophoblasts into maternal blood vessels.
Cytotrophoblast cells not only facilitate the erosion of maternal vessels but also provide a barrier and structural support in the placenta.
The decidua basalis forms the maternal portion of the placenta, influencing nutrient supply and immune tolerance during pregnancy.

Villi and Placental Changes

As pregnancy advances, the villi on the embryonic pole become more complex and increase in surface area to enhance nutrient exchange.
The placenta is primarily composed of chorionic villi that facilitate the exchange of gases, nutrients, and waste between maternal and fetal circulations.
Fusion of the amnion and chorion leads to a reduction in the chorionic cavity, ultimately impacting the amniotic sac's structure.

Placental Structure and Interactions

The junctional zone between fetal and maternal tissue is characterized by intricate interactions, including trophoblastic cells and decidual cells, facilitating effective nutrient transfer.
By the beginning of the fourth month, most cytotrophoblast cells undergo apoptosis or differentiation, leading to a predominance of syncytiotrophoblasts in functional regions.
A trophoblast layer separates maternal and fetal circulations to prevent immunological rejection and maintain circulatory integrity as pregnancy progresses.
Newly formed free villi are expected to mature and increase in surface area for effective nutrient exchange, enhancing fetal growth and development.
Intervillous spaces facilitate the flow of maternal blood around the villi, allowing efficient nutrient and gas exchange without direct maternal-fetal contact.

Decidua Structure and Amniotic Changes

The decidua over the chorion frondosum is characterized by a rich supply of blood vessels and decidual cells, fostering a supportive environment for the developing placenta.
Fusion of the amnion and chorion results in changes to the chorionic cavity, decreasing its size and contributing to the establishment of a protective cavity around the fetus.

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Description

This quiz covers the development of fetal membranes and placenta, focusing on changes in the trophoblast and the formation of the fetal and maternal components. It also includes information about the human embryo at the beginning of the second month of development.