Embryology 4: Gastrulation MCQ
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Questions and Answers

What is the main process that leads to the formation of the three germinal layers?

  • Gastrulation (correct)
  • Cleavage
  • Neurulation
  • Segmentation

Which of the following is NOT one of the three germinal layers formed during gastrulation?

  • Endoderm
  • Ectoderm
  • Dermatoderm (correct)
  • Mesoderm

What structural feature marks the start of gastrulation?

  • Primitive groove
  • Epiblast layer
  • Primitive node
  • Primitive streak (correct)

Which factor is involved in the migration of epiblast cells during the formation of the primitive streak?

<p>FGF 8 (C)</p> Signup and view all the answers

Which congenital condition is associated with the failure of proper gastrulation?

<p>Sirenomielia (C)</p> Signup and view all the answers

In which week does gastrulation extend to the beginning?

<p>Third week (C)</p> Signup and view all the answers

What morphological feature is recognized due to the presence of the primitive streak?

<p>Body axes (A)</p> Signup and view all the answers

During the formation of the primitive streak, what role do epiblast cells play?

<p>They migrate and form the streak. (C)</p> Signup and view all the answers

What is the primary function of the primitive endoderm?

<p>Development of the yolk sac (C)</p> Signup and view all the answers

Which structures are formed by the endoderm?

<p>Pancreas and liver (D)</p> Signup and view all the answers

What is the primary consequence of ethanol acting as a teratogen during development?

<p>Failure of activation of the sonic hedgehog pathway (D)</p> Signup and view all the answers

How is the mesoderm subdivided?

<p>Into paraxial, lateral, and intermediate compartments (D)</p> Signup and view all the answers

What role does the oropharyngeal membrane play?

<p>Is the site where the digestive tract will develop (A)</p> Signup and view all the answers

Which developmental disorder is characterized by the non-development of the rostral part of the brain?

<p>Holoprosencephaly (D)</p> Signup and view all the answers

What does the cloacal membrane ultimately develop into?

<p>The anal canal and urinary tract (C)</p> Signup and view all the answers

What role does the primary cilium play in cellular function during development?

<p>It is important for cell signaling and intercellular communication (D)</p> Signup and view all the answers

Which proteins are associated with the sonic hedgehog pathway?

<p>Sonic, Indian, and Desert (C)</p> Signup and view all the answers

Which of the following is not a component formed by the mesoderm?

<p>Thyroid (C)</p> Signup and view all the answers

What does the prechordal plate represent?

<p>A layer associated with the anterior visceral endoderm (D)</p> Signup and view all the answers

What happens at the end of gastrulation in development?

<p>Formation of the tail bud (B)</p> Signup and view all the answers

Which of the following correctly describes the intermediate mesoderm?

<p>It gives rise to the cardiac mesoderm (D)</p> Signup and view all the answers

What type of cancer can develop from remnants of the notochord?

<p>Chordomas (D)</p> Signup and view all the answers

Which mesodermal layer contributes to the formation of the kidneys and gonads?

<p>Intermediate mesoderm (B)</p> Signup and view all the answers

What process occurs in the trunk region of the paraxial mesoderm?

<p>Somitogenesis (A)</p> Signup and view all the answers

What structure is formed when the lateral plate mesoderm splits?

<p>Intrambryonic coelom (D)</p> Signup and view all the answers

Where do chordomas typically develop?

<p>Base of the skull or vertebral column (B)</p> Signup and view all the answers

What mesodermal component will not undergo segmentation in the head region?

<p>Head mesenchyme (D)</p> Signup and view all the answers

Which of the following structures is formed from the splanchnic mesoderm?

<p>Digestive tract (B)</p> Signup and view all the answers

What is the significance of the primitive heart field?

<p>It guides the migration of cardiac cells. (A)</p> Signup and view all the answers

What structure do ectodermal cells differentiate into that forms the neural crest?

<p>Neural plate (B)</p> Signup and view all the answers

Which of the following structures does NOT derive from the neural crest?

<p>Epidermis (D)</p> Signup and view all the answers

What is the name given to the process that forms the neural plate?

<p>Neurulation (C)</p> Signup and view all the answers

What defines the neural groove during the formation of the neural tube?

<p>An indentation in the neural plate (D)</p> Signup and view all the answers

Which signals trigger the ectoderm to change its characteristics and form the neural crest?

<p>Signals from the notochord and prechordal plate (D)</p> Signup and view all the answers

After the formation of the neural tube, what happens to the neural crests?

<p>They migrate away (D)</p> Signup and view all the answers

Which of the following does NOT originate from ectoderm cells?

<p>Notochord (A)</p> Signup and view all the answers

What role does the notochord play in early embryonic development?

<p>It guides the development of the axial skeleton and neural plate. (B)</p> Signup and view all the answers

What tissue will the neural tube eventually form after closure of the ectoderm?

<p>Central nervous tissue (B)</p> Signup and view all the answers

Which mesoderm develops directly adjacent to the notochord?

<p>Paraxial mesoderm (B)</p> Signup and view all the answers

What happens to the notochord as the primitive streak shortens?

<p>It elongates towards the prechordal plate. (D)</p> Signup and view all the answers

The notochord initially forms as which of the following structures?

<p>A tubular structure with a lumen inside. (A)</p> Signup and view all the answers

In which area of the embryo does the primitive heart field develop?

<p>Rostral to the oropharyngeal membrane. (B)</p> Signup and view all the answers

Which mesodermal layer is formed more laterally than the intermediate mesoderm?

<p>Lateral plate mesoderm (D)</p> Signup and view all the answers

What occurs to the notochord after it fuses with the endoderm?

<p>It pinches off to become a solid rod. (D)</p> Signup and view all the answers

What is the significance of the notochord in vertebrate development?

<p>It acts as a signaling center for organizing surrounding tissues. (D)</p> Signup and view all the answers

Flashcards

Gastrulation

The process where a two-layered embryo transforms into a three-layered embryo. This is essential for the development of different tissues and organs.

Three Germinal Layers

The endoderm, mesoderm, and ectoderm, which are the three primary layers of the embryo that will develop into different tissues and organs.

Endoderm

The innermost germ layer, which will eventually develop into the lining of digestive and respiratory systems, as well as some glands.

Mesoderm

The middle germ layer, which will eventually develop into muscles, bones, blood, heart, and other connective tissues.

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Ectoderm

The outermost germ layer, which will eventually develop into the skin, nervous system, and some glands.

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Primitive Streak

A groove formed on the surface of the epiblast during gastrulation. Its formation marks the start of gastrulation and defines the embryo's body axes.

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Primitive Node

A thickened area at the cranial end of the primitive streak, containing a small pit known as the primitive pit.

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FGF 8

A growth factor that plays a crucial role in the formation of the primitive streak by guiding the migration of epiblast cells towards the midline.

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Primitive endoderm

The first layer of cells to form during gastrulation. It will give rise to various internal structures including the lining of the gut, respiratory tract, liver, pancreas and bladder.

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Yolk sac

A sac-like structure connected to the embryo that provides nutrients and support during development. It is formed by the primitive endoderm.

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Paraxial mesoderm

A region of the mesoderm responsible for forming structures like the dermis, ribs and some muscles.

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Lateral mesoderm

A region of the mesoderm that forms the heart and parts of the circulatory system.

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Intermediate mesoderm

A region of the mesoderm that forms parts of the urinary and reproductive systems.

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Oropharyngeal membrane

A thin membrane at the anterior end of the embryo, destined to form the mouth opening and part of the digestive tract.

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Cloacal membrane

A thin membrane at the posterior end of the embryo, destined to form the anus and part of the urinary/genital system.

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Notochord Elongation

The process of the notochord lengthening, creating a connection between the vitelline sack and the amniotic sack, allowing communication between these structures.

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Neural Plate

A flat sheet of cells formed from the ectoderm during embryonic development, which will eventually fold and close to form the neural tube, giving rise to the nervous system.

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Chordomas

Malignant cancers originating from remnants of the notochord, often developing at the base of the skull or in the vertebral column.

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Somitogenesis

The process of forming somites, segmented blocks of mesoderm that will give rise to muscles, vertebrae, and other structures in the trunk.

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Lateral Plate Mesoderm

A portion of the mesoderm that splits into two layers: splanchnic (ventral) and somatic (dorsal), forming the intraembryonic coelom and contributing to the lining of the body cavities.

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Primitive Heart Field

A field of mesenchyme cells that migrate to the oropharyngeal membrane and form the primitive heart, destined to become different parts of the heart.

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Prechordal Plate

A structure that forms in the rostral region of the embryo, just caudal to the oropharyngeal membrane. It plays a crucial role in head development and the formation of the rostral part of the nervous system.

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Notochord

A tubular structure that elongates from the primitive node towards the prechordal plate. It is essential in guiding the development of the axial skeleton and neural plate. It also plays an inductive and patterning role in the embryo.

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Inductive Role (Notochord)

The notochord releases signals that influence the development of nearby tissues, causing them to differentiate into specific cell types.

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Patterning Role (Notochord)

The notochord helps establish the correct spatial organization and arrangement of tissues in the embryo.

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Extraembryonic Mesoderm

This mesoderm extends outside the embryo and connects with the intraembryonic mesoderm. It forms the chorionic cavity, which helps with nutrient exchange.

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Neural Crest

A group of cells that originate from the ectoderm and migrate to various locations in the body, giving rise to the peripheral nervous system, melanocytes, cornea, teeth and parts of the heart.

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Neural Groove

A groove that forms in the midline of the neural plate, deepening and eventually closing to form the neural tube.

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Neurulation

The process of forming the neural tube, with the neural plate folding to form the neural tube.

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Neural Tube

A hollow tube formed from the neural plate that will develop into the brain and spinal cord.

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What does the prechordal plate do?

The prechordal plate sends signals to the ectoderm, causing it to thicken and form the neural plate, which will eventually develop into the neural tube.

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What is the function of the neural crest?

The neural crest is a group of cells that migrate to various locations in the body and give rise to diverse tissues, including the peripheral nervous system, melanocytes, cornea, teeth and parts of the heart.

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Sonic Hedgehog Pathway

A signaling pathway crucial for proper development of various structures, including the brain, limbs, and organs. It involves communication between cells and is essential for tissue formation and regeneration.

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Primary Cilium

A single, non-motile hair-like structure present on most cells, acting as a cellular antenna. It plays a major role in cell communication, especially during development by receiving signals from surrounding cells.

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Ciliopathies

A group of genetic disorders caused by defects in the formation or function of the primary cilium.

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Holoprosencephaly

A severe birth defect characterized by the failure of the brain to develop properly, resulting in a single, undivided ventricle.

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Tail Bud

A swelling formed at the end of the embryo during gastrulation, marking the future tail region. It's a crucial step in shaping the embryo's body plan.

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Study Notes

Embryonic Development

  • Gastrulation transforms two embryonic layers into three, occurring during weeks 3-4 of development.

  • The stages of gastrulation:

    • The embryo starts as a disk (epiblast).
    • An invagination called the primitive streak appears on the dorsal pole.
    • The primitive streak is divided into the primitive node (which contains a primitive pit) and the primitive groove.
    • This marks the initiation of gastrulation.
    • Cells in the epiblast move to the primitive streak, dedifferentiate, and migrate towards the streak, forming the node and pit.

  • The three germ layers are:

    • Endoderm (internal layer)
    • Mesoderm (middle layer)
    • Ectoderm (external layer)
    • These layers develop into different tissues. Examples include the gut, muscle, and skin
  • Sirenomelia: fusion of the legs and sometimes internal organs.
  • Conjoined twins: incomplete separation during development.
  • Situs inversus: organs are in the opposite position to normal locations.

Epithelial-Mesenchymal Transition (EMT)

  • EMT is the dedifferentiation of epithelial cells and is crucial for development.
  • This is driven by a zinc finger transcription factor called Snail.
  • Snail binds to DNA regions and represses factors linked with epithelial integrity (desmoplakin, cytokeratin, E-cadherin).
  • This leads to the expression of undifferentiated traits (vimentin, fibronectin).
  • Snail activation drives cells to lose their differentiated traits, enabling them to migrate and proliferate through the basement membrane.

Mesenchymal Stem Cells (MSCs)

  • MSCs are undifferentiated cells with multi-potent capabilities.
  • They differentiate into connective tissue components like osteoblasts, chondroblasts, fibroblasts, and adipocytes.
  • They produce an extracellular matrix (ECM) rich in hyaluronic acid, essential for tissue development and regeneration.

Formation of the Endoderm, Mesoderm, and Ectoderm Layers

  • Endoderm forms the lining of the gut.
  • Mesoderm develops tissues like muscle, bone, and blood.
  • Ectoderm gives rise to epidermis, nerve tissue, and sense organs.

Development of the Notochord

  • The notochord is a rod-like structure that forms in the dorsal midline, elongating rostrally toward the cranial end and caudally toward the primitive pit.
  • It's critical to vertebrate development and provides signals to adjacent cells, guiding the development of the nervous system and skeletal structures.
  • The notochord is initially a hollow, tubular structure with an open bottom, which then fuses with the endoderm and condenses into a rod-like structure.

Teratogens, Malformations, and Dysplasias

  • Ethanol is a teratogen, which disrupts development.
  • Malignant cancers deriving from notochord remnants (e.g., chordomas) can arise.
  • Defects in the caudal structure (e.g., caudal dysplasia) can impact the development of organs.
  • Anomalies that result from problems in development can affect the lower limbs and the urinary system, or the lumber vertebrae for instance.
  • Sirenomelia is related to defects in the caudal mesoderm.
  • Abnormal cilia can lead to Situs inversus totalis.
  • Kartagener's syndrome causes immotile respiratory cilia and sperm flagella.

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Embryology 4 - Gastrulation PDF

Description

Test your knowledge on the processes of gastrulation and the formation of the three germinal layers. This quiz covers key concepts, structural features, and congenital conditions associated with improper gastrulation. Challenge yourself with questions that explore the role of epiblast cells, the significance of the primitive streak, and related developmental disorders.

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