SEM_04_Gastrulation and Mesolecithal Eggs Quiz
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Questions and Answers

What is the primary outcome of the gastrulation process?

  • Formation of a stomach (correct)
  • Formation of a brain
  • Formation of a heart
  • Formation of a liver

    • At what stage does gastrulation occur in the development of multicellular animals?

  • Third week post-fertilisation
  • Fourth week post-fertilisation
  • First week post-fertilisation
  • Second week post-fertilisation (correct)

    • What is the estimated occurrence of improper gastrulation in human embryos?

  • One-half
  • One-fourth
  • One-third (correct)
  • Two-thirds

    • What is the precursor of the trilaminar stage in embryonic development?

    <p>Bilaminar stage</p> Signup and view all the answers

    During embryonic development, the endoderm primarily gives rise to which of the following structures?

    <p>Epithelial linings of the digestive and respiratory tracts</p> Signup and view all the answers

    Which axis of the organism is determined during gastrulation by the primitive streak and later by the notochord?

    <p>Cranio-caudal axis</p> Signup and view all the answers

    Which group of cells helps determine the anterior-posterior axis of the mouse embryo through molecular signaling pathways?

    <p>Anterior visceral endoderm (AVE)</p> Signup and view all the answers

    Defects in normal right-left asymmetry during development are related to the absence or defects of what in the cells of the primitive node?

    <p>Cilia</p> Signup and view all the answers

    Which genes specify the anterior-posterior polarity during embryonic development?

    <p>Hox genes</p> Signup and view all the answers

    Which structure is primarily responsible for determining the dorsal-ventral axis in embryonic development?

    <p>Notochord</p> Signup and view all the answers

    Which structures are paired during development?

    <p>Lungs and pancreas</p> Signup and view all the answers

    The AVE expresses different genes along its length to help determine which axis of the mouse embryo?

    <p>Anterior-posterior axis</p> Signup and view all the answers

    'Situs inversus' is a mutation resulting in a mirror-mode inversion of which structures with little or no clinical consequences?

    <p>Thoracic and abdominal viscera</p> Signup and view all the answers

    What causes a lethal developmental side random arrangement in terms of right-left asymmetry?

    <p>Cilia defects in primitive node cells</p> Signup and view all the answers

    What plays a role in primitive streak formation and in determining the head region through a complex network of signaling pathways during embryonic development?

    <p>Ancient visceral endoderm (AVE)</p> Signup and view all the answers

    During gastrulation in mammals, which structure marks the end of the blastocyst and the start of gastrulation?

    <p>Primitive node</p> Signup and view all the answers

    What is the role of the primitive streak in gastrulation?

    <p>Produces the definitive endoderm</p> Signup and view all the answers

    Which structure is formed at the cranial end of the primitive streak during gastrulation?

    <p>Primitive node</p> Signup and view all the answers

    What is the final result of gastrulation in mammals?

    <p>Formation of the three germ layers</p> Signup and view all the answers

    Which cells give rise to the embryonic endoderm during gastrulation?

    <p>Epiblast migrating cells</p> Signup and view all the answers

    What do the initial migrating epiblast cells contribute to during gastrulation?

    <p>Endoderm</p> Signup and view all the answers

    Which layer constitutes the notochord, an important structure in inducing early body structures?

    <p>Axial mesoderm</p> Signup and view all the answers

    What does the paraxial mesoderm form during gastrulation?

    <p>Somites</p> Signup and view all the answers

    What is formed by the lateral plate mesoderm during gastrulation?

    <p>Coelom</p> Signup and view all the answers

    What structures does the ectoderm give rise to during development?

    <p>Integument and nervous system</p> Signup and view all the answers

    Which layer forms most of the excretory system during development?

    <p>Mesoderm</p> Signup and view all the answers

    What is the significance of the notochord in early development?

    <p>Induces earliest body structures</p> Signup and view all the answers

    During gastrulation in amphibians, what do the superficial cells of the blastula do?

    <p>Move towards the blastopores and condense at the dorsal lip</p> Signup and view all the answers

    What is the function of the notochord in amphibians?

    <p>Determining the body plan and establishing bilateral symmetry</p> Signup and view all the answers

    In reptiles and birds, what is the shape of the eggs due to the significant amount of yolk?

    <p>Disc-like shape</p> Signup and view all the answers

    What allows outer cells to migrate inwards to form the three germ layers and the notochord in reptiles and birds?

    <p>Primitive streak formation</p> Signup and view all the answers

    What led to the loss of yolk content in mammalian eggs?

    <p>Emergence of the placenta</p> Signup and view all the answers

    What type of cleavage do mammalian eggs undergo?

    <p>Holoblastic cleavage</p> Signup and view all the answers

    What is formed when the inner cell mass organizes into two layers, the epiblast and hypoblast?

    <p>Bilaminar embryonic disc</p> Signup and view all the answers

    What allows the elongation of the embryo to be achieved?

    <p>Convergent extension</p> Signup and view all the answers

    What do mesolecithal eggs in amphibians have a large amount of?

    <p>Yolk</p> Signup and view all the answers

    Which cells contribute to the formation of the amniotic sac in mammals?

    <p>Trophoblast cells</p> Signup and view all the answers

    What is formed from the mesoderm in amphibians, determining the body plan and establishing bilateral symmetry?

    <p>Notochord</p> Signup and view all the answers

    During which process does the embryo develop into a multi-layered organism from a single cell?

    <p>Gastrulation</p> Signup and view all the answers

    What marks the creation of a unique human being and the start of legal limitations for human embryo experimentation?

    <p>Primitive streak development</p> Signup and view all the answers

    What is the primary goal of gastrulation?

    <p>Formation of the archenteron</p> Signup and view all the answers

    What contributes to the establishment of the primary body axes during gastrulation?

    <p>Formation of the notochord</p> Signup and view all the answers

    In what type of eggs does simpler gastrulation occur?

    <p>Ancestral oligolecithal eggs</p> Signup and view all the answers

    What forms during gastrulation and plays a role in the migration of cells toward the interior of the developing embryo?

    <p>Primitive streak</p> Signup and view all the answers

    What structure forms during gastrulation in all chordate embryos?

    <p>Notochord</p> Signup and view all the answers

    What is the result of gastrulation?

    <p>Gastrula</p> Signup and view all the answers

    What is responsible for the development of many supporting tissues, as it allows the formation of triploblastic animals?

    <p>Mesoderm</p> Signup and view all the answers

    What occurs during gastrulation in chordates such as sea urchins?

    <p>Invagination</p> Signup and view all the answers

    What is the term used to describe the exterior opening formed during gastrulation?

    <p>Blastopore</p> Signup and view all the answers

    What is the cavity formed during gastrulation that is open to the exterior called?

    <p>Blastopore</p> Signup and view all the answers

    During which phase does the blastula reorganize into a multi-layered structure called the gastrula?

    <p>Gastrulation stage</p> Signup and view all the answers

    What is the estimated occurrence of improper gastrulation in human embryos?

    <p>One-third of all human embryos</p> Signup and view all the answers

    What is the primary outcome of the gastrulation process?

    <p>Formation of a multi-layered structure</p> Signup and view all the answers

    What is the significance of cellular movements during gastrulation?

    <p>Differentiation of tissue-specific cell lineages</p> Signup and view all the answers

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

    <p>To establish primary body axes</p> Signup and view all the answers

    In which type of eggs does simpler patterns of gastrulation occur, such as in chordates like sea urchins?

    <p>Ancestral oligolecithal eggs</p> Signup and view all the answers

    What marks the creation of a unique human being and the start of legal limitations for human embryo experimentation?

    <p>Primitive streak development</p> Signup and view all the answers

    What is the significance of the notochord in early development?

    <p>Contributes to the establishment of primary body axes</p> Signup and view all the answers

    What is the primary outcome of the gastrulation process?

    <p>Development into a multi-layered organism</p> Signup and view all the answers

    Which structure forms during gastrulation and plays a role in the migration of cells toward the interior of the developing embryo?

    <p>Primitive streak</p> Signup and view all the answers

    What allows the formation of triploblastic animals with a wider variety of tissue types?

    <p>Appearance of mesoderm during gastrulation</p> Signup and view all the answers

    At what stage does gastrulation occur in the development of multicellular animals?

    <p>Before primitive streak development</p> Signup and view all the answers

    In reptiles and birds, what does the significant amount of yolk in the eggs result in?

    <p>Complex patterns of gastrulation</p> Signup and view all the answers

    What causes a lethal developmental side random arrangement in terms of right-left asymmetry?

    <p>Abnormal primitive streak development</p> Signup and view all the answers

    What is formed by the lateral plate mesoderm during gastrulation?

    <p>Excretory system</p> Signup and view all the answers

    During gastrulation, what marks the end of the blastocyst and the start of gastrulation in most mammals?

    <p>Primitive streak</p> Signup and view all the answers

    What do epiblast cells contribute to during mammalian gastrulation?

    <p>Formation of ectoderm</p> Signup and view all the answers

    Which structure determines the caudal-cranial axis and bilateral symmetry of the embryo during gastrulation?

    <p>Primitive streak</p> Signup and view all the answers

    What is the primary outcome of the gastrulation process in mammals?

    <p>Establishment of primary body axes</p> Signup and view all the answers

    What forms the musculoskeletal, circulatory, and most of the excretory systems during mammalian development?

    <p>Mesoderm</p> Signup and view all the answers

    What is formed by epiblast cells proliferating along primitive streak margins and migrating inwards through the primitive streak during gastrulation?

    <p>Definitive endoderm</p> Signup and view all the answers

    Which layer remains on the surface of the embryonic disc during mammalian development?

    <p>Ectoderm</p> Signup and view all the answers

    What gives rise to the integument, sensory organs, and the nervous system among other structures during mammalian development?

    <p>Ectoderm</p> Signup and view all the answers

    Which layer is situated between the ectoderm and endoderm during mammalian development?

    <p>Mesoderm</p> Signup and view all the answers

    What allows outer cells to migrate inwards through the primitive streak, forming distinct body structures during mammalian gastrulation?

    <p>Mesoderm</p> Signup and view all the answers

    What plays a role in determining the dorsal-ventral axis in embryonic development during gastrulation?

    <p>Notochord</p> Signup and view all the answers

    What structure is responsible for determining the head region through a complex network of signaling pathways during embryonic development?

    <p>Primitive streak</p> Signup and view all the answers

    Which process occurs in reptiles and birds due to the significant amount of yolk in polylecithal eggs?

    <p>Simpler gastrulation</p> Signup and view all the answers

    What is formed by the lateral plate mesoderm during gastrulation in mammals?

    <p>Placenta</p> Signup and view all the answers

    What is the significance of the elongation of the embryo achieved through?

    <p>Convergent extension</p> Signup and view all the answers

    In which animals do mammalian eggs undergo holoblastic cleavage?

    <p>Mammals</p> Signup and view all the answers

    Which cells contribute to the formation of the amniotic sac in mammals?

    <p>Trophoblast cells</p> Signup and view all the answers

    What marks the end of the blastocyst and the start of gastrulation in mammals?

    <p>Primitive streak</p> Signup and view all the answers

    What is formed when the inner cell mass organizes into two layers, the epiblast and hypoblast?

    <p>Bilaminar embryonic disc</p> Signup and view all the answers

    Which structure is primarily responsible for determining the dorsal-ventral axis in embryonic development?

    <p>Notochord</p> Signup and view all the answers

    What allows outer cells to migrate inwards to form the three germ layers and the notochord in reptiles and birds?

    <p>Primitive streak formation</p> Signup and view all the answers

    What contributes to the establishment of the primary body axes during gastrulation?

    <p>Lateral plate mesoderm formation</p> Signup and view all the answers

    Which axis of the organism is determined during gastrulation by the primitive streak and later by the notochord?

    <p>Anterior-posterior axis</p> Signup and view all the answers

    In what type of eggs does simpler gastrulation occur?

    <p>Telolecithal eggs</p> Signup and view all the answers

    Which structure is responsible for determining the head region through a complex network of signaling pathways during embryonic development?

    <p>Anterior visceral endoderm (AVE)</p> Signup and view all the answers

    What is the result of improper gastrulation in human embryos?

    <p>Developmental side random arrangement</p> Signup and view all the answers

    What is the precursor of the trilaminar stage in embryonic development?

    <p>Inner cell mass</p> Signup and view all the answers

    Which genes specify the anterior-posterior polarity during embryonic development?

    <p>Hox genes</p> Signup and view all the answers

    What contributes to the establishment of the primary body axes during gastrulation?

    <p>Primitive streak</p> Signup and view all the answers

    Which structure is primarily responsible for determining the dorsal-ventral axis in embryonic development?

    <p>Notochord</p> Signup and view all the answers

    At what stage does gastrulation occur in the development of multicellular animals?

    <p>Morula stage</p> Signup and view all the answers

    What causes defects or absence of cilia in the cells of the primitive node, leading to abnormalities in right-left asymmetry?

    <p>'Nodal' or 'Lefty' concentration</p> Signup and view all the answers

    What gives rise to the integument, sensory organs, and nervous system among other structures during mammalian development?

    <p>'Primitive node'</p> Signup and view all the answers

    Study Notes

    • A miscarriage typically occurs before a woman realizes she's pregnant, around the time of the primitive streak development.

    • The primitive streak is a significant concept in bioethics, marking the creation of a unique human being and the start of legal limitations for human embryo experimentation.

    • Gastrulation is a process during which the embryo develops into a multi-layered organism from a single cell, resulting in the formation of the three germ layers: ectoderm, mesoderm, and endoderm.

    • Gastrulation begins with cell movements that result in a massive reorganization of the embryo from a blastula (a simple spherical ball of cells) into a gastrula (a multi-layered organism).

    • During gastrulation, cells are brought into new positions, allowing them to interact with cells that were initially not near them, paving the way for inductive interactions.

    • The primitive streak forms during gastrulation and plays a role in the migration of cells toward the interior of the developing embryo.

    • From an evolutionary perspective, the primary goal of gastrulation was to form a primitive gut or archenteron by a simple invagination in the blastocyst.

    • Gastrulation is an essential step in the development of more complex embryos, as it allows the formation of a third layer of cells (mesoderm), which is responsible for the development of many supporting tissues.

    • Different gastrulation patterns have evolved throughout the animal kingdom in response to varying yolk content in eggs, with simpler patterns occurring in Ancestral oligolecithal eggs and more complex patterns in Mesolecithal and Polylecithal eggs.

    • In the simplest pattern, gastrulation occurs in chordates such as sea urchins through a process of invagination, resulting in the formation of a two-layered (bilaminar) structure called a trilaminar gastrula.

    • The blastocyst develops into a gastrula through an inward folding process, forming a u-shaped cavity (primitive stomach) that is open to the exterior (blastopore).

    • The appearance of a third layer of cells (mesoderm) during gastrulation is a significant achievement in the development of more complex embryos, allowing the formation of triploblastic animals with a wider variety of tissue types.

    • The notochord is a defining structure in all chordate embryos and forms during gastrulation, contributing to the establishment of the primary body axes (anterior-posterior, dorsal-ventral, and left-right asymmetry).

    • Mesolecithal eggs in amphibians have a large amount of yolk, making gastrulation more complicated than in sea urchins.

    • Superficial cells of the blastula move towards the blastopores and condense at the dorsal lip.

    • The notochord is formed from the mesoderm in the midline, determining the body plan and establishing bilateral symmetry.

    • The elongation of the embryo is achieved through convergent extension.

    • Polylecithal eggs in reptiles and birds have a significant amount of yolk that results in a disc-like shape.

    • The primitive streak is formed in place of the blastopore, allowing outer cells to migrate inwards to form the three germ layers and the notochord.

    • The emergence of the placenta in mammals led to the loss of yolk content in their eggs.

    • Mammalian eggs undergo holoblastic cleavage instead of meroblastic, but the gastrulation process remains similar to that of polylecithal eggs.

    • The embryonic disc is formed when the inner cell mass organizes into two layers, the epiblast and hypoblast, which together compose the bilaminar embryonic disc.

    • In mammals, the trophoblast cells do not degenerate but contribute to the formation of the amniotic sac.

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