General Embryology – Trophoblast and Chorion

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Questions and Answers

What structure forms the outer layer of the chorionic villus in early pregnancy?

Cytotrophoblast (correct)

Syncytiotrophoblast (correct)

Decidua

Somatic layer of extraembryonic mesoderm

Which of the following structures is involved in the exchange of substances between maternal blood and the embryo?

Cytotrophoblastic shell

Extraembryonic mesoderm

Tertiary chorionic villus (correct)

Lacunae (correct)

What is the primary function of the placental barrier?

To form the decidua

To restrict maternal blood flow to the embryo

To regulate the exchange of nutrients and waste (correct)

To provide structural support for the embryo

In the context of placental development, what does the term 'intervillous space' refer to?

The space filled with maternal blood Signup and view all the answers

What forms the primary chorionic villus during early development?

Cytotrophoblast and extraembryonic mesoderm Signup and view all the answers

What forms the outer layer of the chorion during embryonic development?

Somatic layer of extraembryonic mesoderm Signup and view all the answers

What is the primary function of the chorionic villi?

To facilitate the exchange of gases and nutrients Signup and view all the answers

Which layer of the extraembryonic mesoderm is associated with the splanchnic layer?

Somatic layer Signup and view all the answers

Which structure contains lacunae filled with maternal blood in the intervillous space?

Tertiary chorionic villus Signup and view all the answers

What structure serves as a connection between the chorionic villi and the maternal blood vessels?

Body stalk Signup and view all the answers

Which of the following describes the area where the primary chorionic villus develops?

In the cytotrophoblast layer Signup and view all the answers

Which term refers to the specialized layer that forms during the development of the placenta?

Syncytiotrophoblast Signup and view all the answers

What is the significance of the extraembryonic coelom in embryonic development?

It provides a space for the developing embryo. Signup and view all the answers

What is the role of the trophoblast during implantation?

To establish contact with maternal tissues Signup and view all the answers

Which layer is responsible for forming the chorion?

Extraembryonic mesoderm Signup and view all the answers

Which part of the decidua represents the portion of the endometrium that is directly beneath the implanted blastocyst?

Decidua basalis Signup and view all the answers

The primary yolk sac is also known as which of the following?

Exocoelomic cavity Signup and view all the answers

What are the two layers present in the bilaminar embryonic disc during the second week of development?

Ectoderm and endoderm Signup and view all the answers

What is the fate of the chorionic villi during development?

To develop into the placenta Signup and view all the answers

Which layer of the blastocyst contributes to the formation of the amnion?

Ectoderm Signup and view all the answers

What type of embryonic tissue is the syncytiotrophoblast primarily composed of?

Fusion of trophoblast cells Signup and view all the answers

Study Notes

Implantation and Its Steps

Implantation is the process where the blastocyst embeds itself into the uterine wall.
Steps include attachment of the blastocyst, invasion of trophoblasts, and interaction with the maternal decidua.

Sites of Implantation

Normal implantation occurs in the decidua basalis of the uterus.
Abnormal implantation sites include the fallopian tubes (ectopic pregnancy) or other locations outside the uterine cavity.

Decidua and Its Parts

The decidua is the modified mucosal lining of the uterus during pregnancy.
Key parts include:
- Decidua basalis: Site of implantation.
- Decidua capsularis: Covers the chorion.
- Decidua parietalis: Lines the rest of the uterine cavity.

Trophoblast Structure

Trophoblast has two layers:
- Syncytiotrophoblast: Outer layer that invades maternal tissues.
- Cytotrophoblast: Inner layer that forms the chorionic villi.

Extraembryonic Mesoderm and Chorion

Extraembryonic mesoderm is crucial for the development of chorionic structures.
The chorion is formed by the combination of trophoblast and mesoderm layers.
Chorion has somatic and splanchnic layers contributing to placental structure.

Chorionic Villi and Their Fate

Types of chorionic villi:
- Primary chorionic villi: Initial projections from trophoblast.
- Secondary chorionic villi: Develop with mesodermal core.
- Tertiary chorionic villi: Contain fetal blood vessels and are involved in nutrient exchange.
Chorionic villi mature and form the placental barrier, facilitating maternal-fetal exchange.

Amniotic Structures

The amniotic cavity is formed from amniogenic cells that differentiate into ectoderm and endoderm.
The primary yolk sac provides initial nutrient transfer before the functional placenta develops.

Role of Lacunae

Lacunae are spaces within the intervillous space filled with maternal blood.
They play a critical role in nutrient and gas exchange between mother and fetus.

Summary of Key Layers

Ectoderm develops from the epiblast.
Endoderm develops from the hypoblast.
Both layers form the bilaminar embryonic disc by the second week.

Placental Structures

The placenta develops from the chorionic villi and decidua, serving multiple functions including nutrient, gas exchange, and waste removal.
Blood vessel formation starts in tertiary chorionic villi, establishing a connection to the fetal circulation.

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Description

This quiz covers the fundamentals of implantation and embryonic development, focusing on the trophoblast and chorion. Participants will learn to identify normal and abnormal implantation sites, the structure of the decidua, and the types of chorionic villi. Enhance your knowledge in embryology within the context of medicine and surgery.