Embryology Chapter on Epiblast and Development

Questions and Answers

What structure is formed from epiblast cells that move cranially?

Definitive endoderm

Mesoderm

Oropharyngeal membrane (correct)

Notochord

What happens to the hypoblast during the invagination of epiblast cells?

It is replaced by mesoderm.

It becomes part of the oropharyngeal membrane.

It is displaced to form definitive endoderm. (correct)

It fuses with the epiblast.

Which structure indicates the potential future opening of the oral cavity?

Primitive streak

Precordial plate

Oropharyngeal membrane (correct)

Amniotic cavity

At the end of the second week of development, what is primarily visible on the dorsal side of the embryo?

Primitive streak Signup and view all the answers

What does the precordial plate induce during embryonic development?

Induction of the forebrain Signup and view all the answers

Which timeframe corresponds to the formation of the trilaminar germ disc?

3rd week of development Signup and view all the answers

What main process occurs when the epiblast cells move inward?

Mesoderm creation Signup and view all the answers

Which layer replaces the hypoblast after the inward movement of epiblast cells?

Definitive endoderm Signup and view all the answers

What structure serves as the definitive chord in the development of the axial skeleton?

Notochord Signup and view all the answers

At what developmental stage does the left-right axis (LR) occur?

During the morula stage Signup and view all the answers

Which factor is necessary for the ventralization of the mesoderm that contributes to kidney formation?

Fibroblast growth factor 8 (FGF8) Signup and view all the answers

What forms at the caudal end of the embryonic disc during early development?

Cloacal membrane Signup and view all the answers

What does the anterior-posterior (AP) axis formation lead to at the cranial end of the endoderm?

Formation of the head region Signup and view all the answers

What role do mesoderm cells play in the development of the prechordal plate?

They support forebrain induction. Signup and view all the answers

Which of the following statements accurately describes the notochordal plate formation?

It detaches from the endoderm to become the notochord. Signup and view all the answers

Which structure is formed through the migration of prenotochordal cells?

The prechordal plate. Signup and view all the answers

What is the relationship between the tropoblast and the placenta?

The tropoblast will develop into the future placenta. Signup and view all the answers

What does the primary villi contribute to in embryonic development?

Supply of nutrients and oxygen to the embryo. Signup and view all the answers

How do epiblast cells contribute to the structure of the notochordal plate?

They invaginate to create multiple layers within the plate. Signup and view all the answers

What happens when the notochordal plate detaches from the endoderm?

It becomes the definitive notochord. Signup and view all the answers

What is the primary role of the mesoderm germ layer?

Support and structure for the body Signup and view all the answers

What function does the connecting stalk serve during the embryonic development?

It connects the embryo to the maternal tissues. Signup and view all the answers

Which factors are involved in the induction of the neural plate?

Inhibition of BMP4 and TGF B, upregulation of FGF Signup and view all the answers

What occurs during the process of neurulation?

Neural folds elevate and the mid-region forms the neural groove Signup and view all the answers

At what developmental stage does the anterior cranial neuropore close?

Day 25 Signup and view all the answers

What does the endoderm germ layer primarily give rise to?

Internal organs such as the liver and pancreas Signup and view all the answers

Which structure forms at the midline during the fusion of the neural folds?

Cervical region Signup and view all the answers

What is the significance of the notochord in embryonic development?

It guides the development of the vertebral column Signup and view all the answers

Which stage is described as being 1.25 mm long and 0.68 mm wide in embryo development?

Dorsal view of an 18-day embryo Signup and view all the answers

What is the role of nodal in embryonic development?

It initiates and maintains the primitive streak. Signup and view all the answers

Which factor is primarily responsible for the restriction of nodal expression to the left side of the embryo?

FGF8 Signup and view all the answers

What does situs inversus refer to in the context of organ placement?

Organs are positioned in a mirror image arrangement. Signup and view all the answers

Which condition is characterized by the heart being located on the right side instead of the left?

Dextrocardia Signup and view all the answers

What can result from abnormal expression of nodal during embryonic development?

Defects in laterality such as situs inversus Signup and view all the answers

What is the primary process that leads to the formation of the neural tube?

Neurulation Signup and view all the answers

Which of the following best describes the function of TGF B?

It acts as a signaling molecule in various developmental processes. Signup and view all the answers

How does the primitive streak relate to the overall structure of the embryo?

It marks the midpoint for the separation of left and right sides. Signup and view all the answers

Study Notes

Epiblast Cell Movements

Epiblast cells migrate laterally, cranially, and caudally.
Cranially migrating cells form the precordial plate, which induces forebrain development.
The oropharyngeal membrane marks the future opening of the oral cavity.

Germ Disc and Development

The dorsal side of a 16-day embryo shows movement of surface epiblast cells; the primitive streak creates a shallow groove in the caudal region.
By day 15, epiblast invagination displaces hypoblast cells, establishing definitive endoderm.
Epiblast gives rise to three germ layers: ectoderm, mesoderm, and endoderm, contributing to organogenesis.

Nutritional Support

Primary villi, villous capillaries, and connecting stalk (chorionic plate) supply nutrients and oxygen.
The trophoblast will develop into the placenta, essential for embryonic nourishment.

Notochord Formation

Notochordal plate detachment from the endoderm defines the formation of the definitive notochord.
Prenotochordal cells invaginate, extending cranially to the precordial plate and caudally to the primitive pit.

Body Axes Establishment

Body axes include anterior-posterior (AP), dorso-ventral (DV), and left-right (L-R) orientations.
The anterior visceral endoderm (AVE) appears at the cranial end, marking the head region.
Nodal is crucial for initiating and maintaining the primitive streak; improper nodal expression leads to defects like situs inversus and dextrocardia.

Molecular Regulation of Neural Induction

Neurulation involves the neural plate forming the neural tube, initiated by FGF upregulation and BMP4 inhibition.
Neural folds elevate to create the neural groove, eventually fusing to form the neural tube.
Anterior cranial neuropore closes by day 25; posterior neuropore closes by day 28.

Derivatives of Germ Layers

Mesoderm: Supports tissues such as myotomes (muscle), sclerotomes (cartilage), and dermatomes (skin).
Endoderm: Forms internal organs, including the gastrointestinal tract, respiratory tract, and glands like the liver and pancreas.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers key concepts related to epiblast cell movements, germ disc structure, and the role of nutritional support in embryonic development. It explores the formation of the notochord and its significance in organogenesis, as well as the differentiation of the germ layers. Test your understanding of these fundamental embryological processes!