Chapter 13.1. Chick Development Flash Cards

Page 1: Introduction to Chicken Development

• Vertebrate Development: Focus on the development of chickens, specifically the species Gallus gallus.

Page 2: Amniotes

• Amniotes: Group of vertebrates that includes reptiles, birds, and mammals.

  • Characteristics: Have an amniote egg that allows for terrestrial reproduction.

  • Types of Amniotes:

    • Reptiles: An example is the chicken.

    • Birds: Characterized by feathers and flight.

    • Monotremes: Egg-laying mammals (like platypus and echidna) that possess mammary glands.

    • Placental mammals: Examples include Mus musculus (house mouse).

Page 3: Extraembryonic Membranes

• Amniote Egg Development: Membranes form during the development of reptiles, birds, and mammals.

  • Types of Extraembryonic Membranes:

    • Yolk Sac: Provides nutrients.

    • Chorion: Contains blood vessels, functions in respiration, contributes to placenta in placental mammals.

    • Allantois: Waste storage.

    • Amnion: Encloses the embryo in a protective fluid.

    • Shell and Amniotic Cavity: Protects and contains the embryo.

Page 4: Amnion and Yolk Sac

• Amnion: A membrane surrounding the chick embryo, providing a fluid cushion and preventing desiccation.

• Yolk Sac: In chickens, encases the yolk and features blood vessels for nutrient absorption.

Page 5: Allantois and Chorion Functions

• Allantois: Functions mainly to store waste produced by the embryo.

• Chorion: Contains blood vessels that facilitate gas exchange, absorbing oxygen and releasing carbon dioxide; forms part of the placenta in placental mammals.

Page 6: Structure of the Chick Egg

• Blastodisc: A small disc of cytoplasm on the surface of the yolk that undergoes division.

  • Components:

    • Chalaza: Helps stabilize the yolk.

    • Albumin: Egg white that provides additional nutrients.

    • Vitelline Membrane: Surrounds the yolk.

    • Shell Membranes & Air Space: Protect the contents.

Page 7: Early Cell Division

• Cell Division: Early stages show a 1-cell thick layer except at the edges.

  • Areas of the Blastodisc:

    • Area pellucida: Clear central zone.

    • Area opaca: Peripheral zone.

    • Marginal zone: Outer edge of the disk.

Page 8: Cell Layer Formation

• Cell Layers: Early cell divisions lead to a fluid-containing blastocoel below the single-layered upper epiblast.

Page 9: Developmental Similarities

• Pre-gastrulation and Gastrulation: Similarities between chicken and mammalian development, particularly in extraembryonic membranes and cell movements during gastrulation.

Page 10: Formation of the Hypoblast

• Hypoblast Formation: Some cells migrate to the subgerminal cavity to contribute to the hypoblast as the egg is laid.

Page 11: Layers and Structures

• Blastoceal: Space found between the upper epiblast and lower hypoblast.

  • Only Epiblast: Responsible for forming the embryo.

Page 12: Hypoblast Development Stages

• Development Stages: Hypoblast islands begin to form; sequential stages classify the variety of layers.

Page 13: Primitive Streak Initiation

• Primitive Streak and Groove: Important process in birds and mammals, where cells migrate to the disk's center, producing the thickening known as the primitive streak and groove.

Page 14: Cell Migration to Blastocoel

• Cell Movement: Involves individual migration through the primitive groove, transitioning from an epithelial to a mesenchymal state, with changes in cadherin expression.

Page 15: Stages of Formation

• Stages: Various stages of development showing the formation of the primitive streak and relationships among epiblast, hypoblast, and other structures.

Page 16: Early Stages of Cell Movement

• Cell Movements: Formation of the primitive streak is associated with the migration of cells from the marginal zone towards the center of the blastoderm.

Page 17: Endodermal and Mesodermal Cells Migration

• Cell Distribution: Endodermal and mesodermal cells migrate through the primitive streak, with some integrating into the hypoblast and others forming a loose layer in the blastocoel.

Page 18: Future Endoderm Formation

• Endoderm Formation: Some migrating cells displace existing hypoblast cells to form the future endoderm.

Page 19: Role of Hensen’s Node

• Hensen's Node: Anterior segment of the primitive streak serves a role similar to the dorsal blastopore lip in frogs, demonstrating early embryonic development processes.

Page 20: Fate Mapping

• Fate Map: Cell movements during the primitive streak can be mapped, showing differentiation into various structures including notochord and mesoderm layers.

Page 21: Developmental Progression

• Anatomical Structures: Illustrates how anterior and posterior embryonic structures form at different development stages.

Page 22: Asymmetry in Development

• Embryonic Axis and Timing: Anterior regions develop earlier than posterior regions based on the timing of cell migration through the primitive streak during gastrulation.

Page 23: Layers of the Developing Embryo

• Gastrulation Phase: Formation of three definitive layers: ectoderm, mesoderm, and endoderm, with migration dynamics affecting overall morphology.

Page 24: Embryonic Structures

• Embryonic Anatomy: Overview of key structures such as the heart and amniotic cavity, vital for development.

Page 25: Hensen's Node Functionality

• Cell Signaling and Organizers: Hensen’s node can induce axial development when transplanted, similar to the organizer function in frogs.

Page 26: Organizer Signaling Molecules

• Molecular Functions: Chordin and Noggin from Hensen's node inhibit BMP signaling, enhancing dorsal tissue formation, yet requiring FGF for neural specification.

Page 27: Role of Noggin

• Signaling Pathways: Interactions of Noggin with BMP signaling crucial for neural induction processes in chicks.

Page 28: FGF Signaling

• Fibroblast Growth Factors (FGF): Produced in early embryonic stages; they are essential for neuronal gene expression in targeted areas of the embryo.

Page 29: Retinoic Acid Dynamics

• Retinoic Acid: A hydrophobic signaling molecule derived from vitamin A, serves as a morphogen affecting gene expression gradients along the anterior-posterior axis.

Page 30: Gradients and Morphogenic Effects

• Morphogen Gradient: Only low concentrations enhance anterior development, while high levels promote posterior specifications.

Page 31: Hox Gene Expression

• Hox Genes: Critical for determining body plan in vertebrates; retinoic acid influences expression patterns of these genes during development.

Page 32: Homology Across Species

• Homologous Genes: Comparison of vertebrate Hox genes to Drosophila homeotic genes highlights evolutionary conservation and functional roles in development.

Page 33: Regional Hox Expression

• Differential Hox Expression: Specific Hox genes such as Hoxb4 and Hoxb9 are expressed at defined embryonic stages, reflecting varying developmental roles in the anterior-posterior axis.