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Questions and Answers
What is formed during the first week of implantation?
Which structures differentiate from the trophoblast during the implantation process?
What condition is associated with the loss of mesoderm during gastrulation?
During which week of implantation does the bilaminar embryo form?
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What component links the embryo to the trophoblast in mammals?
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What is the primary characteristic of gastrulation during embryonic development?
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What changes occur during the cellular differentiation stage of gastrulation?
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Which of the following processes is NOT considered a morphogenetic movement during gastrulation?
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In protostomes, what does the first opening in the embryo develop into?
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What is the significance of Hensen's node during avian gastrulation?
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How does the role of the nucleus change during the gastrulation stage?
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Which layer forms the epiblast and primary hypoblast during avian gastrulation?
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What defining event marks the onset of gastrulation in vertebrates?
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Study Notes
Gastrulation
- First described by Ernst Hackel in 1872
- The most defining event in the third week of gestation
- A process where cells undergo morphogenetic movements
- Formation of three germ layers: ectoderm, mesoderm, and endoderm
Character of Gastrulation Stage
- The first stage of cellular differentiation
- Embryonic cells begin to follow specific layers through morphogenetic movements
- Cellular division loses synchronization and coordination becomes dominant over metabolic changes
- Nucleus plays a more significant role in the process of development control compared to the previous stages
- Chromosomes are more actively involved than before in controlling development
Morphogenetic Processes
- Invagination: Infolding of a sheet of cells
- Involution: Inward movement of a cell sheet over the surface of another cell sheet
- Ingression: Migration of individual cells into the interior of the embryo
- Delamination: Splitting of one cell sheet into two
- Epiboly: The spreading or expansion of a cell sheet over other cells
Protostomes and Deuterostomes
- Protostomes: The first opening in the embryo becomes the mouth
- Deuterostomes: The first opening in the embryo becomes the anus
Axis Formation
- Defines the anterior-posterior and dorsal-ventral axes of the embryo
- Occurs through a series of cell movements and signaling events
Fish Gastrulation
- Epiboly of blastoderm cells over the yolk
- Deep cells move outwardly to intercalate with superficial cells
- YSL: Yolk Syncytial Layer
- EVL: Enveloping Layer
- Germ Ring: The ring of cells that forms at the margin of the blastoderm
Amphibian Gastrulation
- The blastopore forms at the vegetal pole of the blastula
- Cells move through the blastopore to form the mesoderm and endoderm
- Dorsal Lip: The dorsal-most region of the blastopore
Avian Gastrulation
- Area Pellucida: The region of the blastoderm that will form the embryo
- Forms the epiblast and primary hypoblast through delamination
- Posterior cell sheets migrate anteriorly to form the secondary hypoblast
- Primitive Streak: A thickening of the epiblast that forms in the posterior region of the embryo
- Primitive Groove: A depression within the primitive streak
- Hensen’s Node: The anterior end of the primitive streak
- Primitive Pit: A funnel-shaped depression where cells can pass through
Mammalian Gastrulation
- Similar to avian gastrulation but with a more complex process
- Involves formation of extraembryonic membranes and the embryo
- Trophoblast: The outer layer of the blastocyst
- ICM: Inner Cell Mass
- Embryoblast: The part of the ICM that will form the embryo
Clinical Correlation
- Sirenomelia: Loss of mesoderm (caudal dysgenesis)
- Sacrococcygeal Teratoma: Remnant of the primitive streak
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Description
This quiz explores the critical stage of gastrulation in embryonic development, detailing its processes and significance. Key topics include the formation of the three germ layers and the morphogenetic processes involved. Test your knowledge on cellular differentiation and the role of the nucleus during this vital phase.
