Embryology Week 3: Gastrulation and Germ Layers

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the lacunar spaces that develop during the second week of embryonic development?

They play a crucial role in establishing the uteroplacental circulation. (correct)

They form the basis for the development of the intraembryonic coelom.

They contribute to the formation of the endoderm and yolk sac.

They serve as precursors for the development of somites and the nephrogenic cord.

Which germ layer is responsible for the formation of the amnion?

Endoderm

Mesoderm

Epiblast (correct)

Hypoblast

What is the primary function of the somites?

Developing into the neural tube

Generating the epithelial lining of the digestive tract

Giving rise to skeletal muscle, bone, and dermis (correct)

Forming the circulatory system

Which of the following structures is NOT a derivative of the mesoderm?

Amnion Signup and view all the answers

What is the direct precursor to the formation of the pericardial, pleural, and peritoneal cavities?

Intraembryonic coelom Signup and view all the answers

Which of the following statements accurately describes the development of the secondary yolk sac?

It is a direct derivative of the hypoblast. Signup and view all the answers

What is the primary function of the chorionic cavity?

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

Which of the following structures is NOT present at the end of the second week of embryonic development?

Primitive streak Signup and view all the answers

Which of the following statements accurately describes the role of the nephrogenic cord in early embryogenesis?

It serves as the precursor to the kidney and other urinary structures. Signup and view all the answers

What is the primary distinction between the epiblast and the hypoblast?

The epiblast is responsible for the development of the nervous system and the hypoblast is involved in the formation of the digestive system. Signup and view all the answers

What structure forms at the cranial end of the primitive streak during the early stages of development?

Primitive Node (Hensen's Node) Signup and view all the answers

Which mass is responsible for forming the future embryo during the third day of development?

Inner cell mass (embryoblast) Signup and view all the answers

What is the function of the outer cell mass (trophoblast) in early development?

To facilitate implantation Signup and view all the answers

At what developmental stage is the morula formed?

Third day Signup and view all the answers

What does the Primitive Node primarily serve as during development?

An organizer for structure formation Signup and view all the answers

What marks the beginning of neural tube formation?

Development of the neural groove Signup and view all the answers

Which cells become the amnion during early embryonic development?

Epiblast cells Signup and view all the answers

What is the primary function of the amnion?

To surround the embryo with amniotic fluid for cushioning and protection Signup and view all the answers

Where are neural crest cells located during early development?

At the edges of the neural plate Signup and view all the answers

Which statement is true regarding the relationship between the neural groove and neural crests?

Neural crest cells arise from the edges of the neural plate near the neural groove Signup and view all the answers

What is the key characteristic of cleavage in mesoblast formation?

No increase in cytoplasmic volume despite cellular division Signup and view all the answers

What type of cells are blastomeres during the mesoblast formation?

Totipotent, able to form a complete embryo Signup and view all the answers

Where is the mesoderm formation primarily initiated during embryonic development?

At the caudal end of the embryonic disc Signup and view all the answers

What structures will the mesodermal cells eventually form in the embryo?

Muscle and connective tissue Signup and view all the answers

What is the role of the cloacal membrane during embryonic development?

It develops into the future anus at the caudal end Signup and view all the answers

Which of the following statements accurately reflects the nature of blastomeres during the early stages of development?

Every blastomere has the potential to develop into a complete embryo Signup and view all the answers

What happens to the size of the cells during cleavage in mesoblast formation?

Cells undergo size reduction with each division Signup and view all the answers

What tissue structures are primarily formed from mesodermal cells?

Connective tissue and cardiovascular systems Signup and view all the answers

What is the main function of the blastomeres in the morula stage?

To maximize contact with one another forming tight junctions Signup and view all the answers

Which structure is critical for the development of the notochord?

The primitive node and chordal process Signup and view all the answers

Where does the oropharyngeal membrane develop in relation to the embryonic disc?

At the cranial end of the embryonic disc Signup and view all the answers

During which days does fluid accumulation between blastomeres in the morula begin?

Days 4–5 Signup and view all the answers

What is the primary role of compaction in the morula stage?

To enhance structural integrity of the developing embryo Signup and view all the answers

What happens to the zona pellucida as the morula transitions to the blastocyst?

It disintegrates completely Signup and view all the answers

What is directly formed from mesodermal cells migrating cranially from the primitive streak?

The cardiogenic zone Signup and view all the answers

Which structure is responsible for signaling surrounding tissue differentiation?

The notochord Signup and view all the answers

What type of junctions do blastomeres form during the morula stage?

Tight junctions Signup and view all the answers

What is one of the critical components that forms during the transition from morula to blastocyst?

The blastocoel Signup and view all the answers

What is the primary function of the primitive streak during gastrulation?

To establish the embryo's craniocaudal axis and symmetry. Signup and view all the answers

Which of the following structures is NOT derived from the intraembryonic mesoderm?

Lining of the gastrointestinal tract Signup and view all the answers

What specific cell layer forms the neural plate, the precursor to the central nervous system?

Epiblast Signup and view all the answers

The formation of the endoderm during gastrulation results in which crucial developmental event?

Formation of the lining of the gastrointestinal and respiratory systems Signup and view all the answers

Which of the following statements correctly describes the relationship between the epiblast and the hypoblast during gastrulation?

The epiblast cells replace the hypoblast cells, forming the definitive endoderm. Signup and view all the answers

What is the primary function of the zona pellucida in the early stages of embryonic development?

To prevent premature implantation and protect the zygote. Signup and view all the answers

Which of the following best describes the process of syngamy?

The fusion of the male and female pronuclei, resulting in a diploid zygote. Signup and view all the answers

Which of the following stages of early embryonic development occurs before the formation of the primitive streak?

Cleavage Signup and view all the answers

During gastrulation, cells migrating from the epiblast between the ectoderm and endoderm will differentiate into which type of cells?

Mesoderm Signup and view all the answers

What is the correct chronological sequence of developmental events in early embryogenesis?

Cleavage, gastrulation, neural plate formation, organogenesis Signup and view all the answers

What is the difference between the primitive line and the primitive streak?

The primitive line is a precursor to the primitive streak. Signup and view all the answers

Which of the following statements accurately describes the role of the primitive streak in gastrulation?

The primitive streak is a temporary structure that disappears after the formation of the three germ layers. Signup and view all the answers

Which statement accurately describes the relationship between the primitive streak and the epiblast cells?

The primitive streak is formed by epiblast cells, and these cells migrate through the streak to form the three germ layers. Signup and view all the answers

What is the significance of the formation of the neural groove during gastrulation?

It is the first indication of the development of the central nervous system, which will play a crucial role in regulating body functions. Signup and view all the answers

Which of the following statements best describes the process of gastrulation?

The process by which the bilaminar embryonic disc is converted into a trilaminar disc with three germ layers. Signup and view all the answers

Which of the following is NOT a direct result of gastrulation?

Formation of the heart. Signup and view all the answers

Study Notes

Third Week of Embryonic Development

Gastrulation Begins: The bilaminar embryonic disc transforms into a trilaminar disc
Primitive Streak Formation: A thickened band of epiblast cells appears on the embryo's dorsal surface, establishing its axis
Germ Layer Formation: Epiblast cells migrate, displacing hypoblast cells to form the definitive endoderm (lines gastrointestinal and respiratory systems). Epiblast cells also migrate between the epiblast and endoderm creating the mesoderm (forms muscles, bones, and blood vessels)
Ectoderm Formation: The ectoderm thickens into a neural plate, the precursor to the nervous system
Neural Plate to Neural Groove: The neural plate folds inward, creating a neural groove
Neural Crest Cells: Specialized ectodermal cells at neural plate edges, migrating to become peripheral nerves, melanocytes, and parts of the craniofacial skeleton
Neural Tube Formation: The neural plate edges elevate and fuse to form the neural tube, the central nervous system's precursor
Mesoderm Differentiation: The mesoderm splits into three regions: para-axial (somites-vertebrae, skeletal muscles, dermis), intermediate (urogenital system), and lateral (heart, blood vessels, body cavity)
Somites: Segmented bodies of para-axial mesoderm
Nephrogenic Cord: Part of the intermediate mesoderm, forming early kidney structures
Intraembryonic Coelom: A cavity within lateral mesoderm, forming pericardial, pleural, and peritoneal cavities.
Somatic and Splanchnic Layers: The lateral mesoderm splits into two layers, aligning with ectoderm and endoderm respectively
Trilaminar Disc Formation: The embryo develops into a trilaminar disc consisting of the ectoderm, mesoderm, and endoderm
Primitive Node (Hensen's Node): A cranial region of the primitive streak that organizes notochord and axial structure formation
Chordal Process and Chordal Canal: The primitive node extends a chordal process cranially, which develops into the notochord, a rod-like signaling center for neural tube and surrounding tissue differentiation, and chordal canal
Neurenteric Duct: A temporary connection between amniotic cavity and yolk sac, important for structural rearrangement
Oropharyngeal Membrane: A membrane at the embryo's cranial end, without mesoderm, forming the future mouth opening
Cloacal Membrane: Region at the caudal end, lacking mesoderm, becoming the future anal membrane
Cardiogenic Zone: Mesodermal cells migrating cranially from the primitive streak, where the heart's primordium develops
Timeline: The third week marks the key transition for development from a bilaminar structure with two germ layers to the trilaminar structure with three germ layers, while initiating neural tube and mesoderm differentiation.

Studying That Suits You

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

Description

Explore the intricate processes of the third week of embryonic development, focusing on gastrulation and the formation of the three germ layers. This quiz covers key events such as the establishment of the primitive streak, the differentiation of epiblast cells, and the early development of the nervous system. Test your knowledge and understanding of these critical developmental milestones.