CHAPTER 9 Flashcards by Haru Haru

These cells are develop to form the vertebrate nervous
system as well as the epidermis of an organism.

Ectoderm

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3 major domains of ectoderm

a. Surface
b. Neural Crest
c. Neural Tube

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→ is also known as the epidermis
→ the outer layer of our skin

Surface

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→ the region that connects the neural tube and the
epidermis

Neural crest

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→ forms the brain and the spinal cord

Neural tube

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Parts of the Surface

Epidermis
Hair
Sebaceous gland
Olfactory epithelium
Mouth epithelium
Lens and cornea

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Parts of the Neural Crest

● peripheral nervous system
○ schwann cells
○ neuroglial cells
○ sympathetic nervous system
○ parasympathetic nervous system
● adrenal medulla
● melanocytes
● facial cartilage
● dentine of teeth

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Parts of the Neural Tube

● brain
● neural pituitary
● spinal cord
● motor neurons
● retina

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________ → it is a structure that serves as the basis for
the nervous system

Neural Plate

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________ → is a flexible rod-shape found in embryos of
all chordates composed of ________

Notochord
mesodermal cells

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______ → a part of both digestive and respiratory system

Pharynx

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4 Stages of Pluripotent Development into
Neuroblast

Competence
Specification
Commitment
Differentiation

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→ multipotent cells become neuroblast once they
are exposed to the appropriate signals
→ have the ability to response to the particular
signals

Competence

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→ the cells received the signals and successfully
develop into neuroblasts, but… progression along
the neural differentiation pathway repressed by
other signal
→ which means, that specification is a transition
between cells to become anything with their own
fates

Specification

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→ the neuroblasts enter the neural differentiation
pathway and become neurons even in the presence
of signals
→ cells will develop into neuroblasts and cannot be
reversed

Commitment

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→ the neuroblasts leave the mitotic cycle and
express those genes characteristics of neurons
→ this is a process in which the unspecialized cells
become specialized to carry out distinct functions

Differentiation

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2 Ways of Neural Tube Formation

a. Primary Neurulation
b. Secondary Neurulation

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→ the cells surrounding the neural plate direct the
neural plate to proliferate, invaginate, and pinch off
the surface to form a hollow tube
→ the formation of the neural tube direct came from
the ectoderm

Primary neurulation

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_________
→ the neural tube arises from the coalescence of
_______ into a solid cord that subsequently forms
cavities that coalesce to create a hollow tube
→ neural tube arises from mesenchyme cells underneath
the ectoderm

Secondary neurulation
mesenchyme cells

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→ the anterior portion of the neural tube is made by
_________
→ the posterior portion of the neural tube is made by
_________
→ joining these two separated tubes together forms
the _________

primary neurulation
secondary neurulation
neural tube

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3 Sets of Cells in Ectoderm

● the internally positioned neural tube
● the externally positioned epidermis of the
skin
● the neural crest

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________ → forms when the edges of neural plate
thicken and move upward

Neural folds

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________ → appears in the center of the plate,
dividing the future right and left sides of the embryo

Neural groove

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4 Stages of Neurulation

Formation and folding of the neural tube
Shaping and elevation of the neural tube
Convergence of the neural fold, creating a neural groove
Closure of the neural groove to form a neural tube

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Primary Neurulation is regulated by two forces

Intrinsic wedging Extrinsic forces

_________ anchored to the surface ectoderm, and increase their height and become wedge-shaped

dorsolateral hinge points (DLHPs)

_______ - is intimately linked to changes in cell shape

cell wedging

_______ - an inhibitor of microtubule polymerization

colchicine

___________ - an inhibitor of the microfilament formation - prevents the apical constriction of these cells, thereby inhibiting wedge formation

cytochalasin B

__________ - the actin-binding protein Shroom critical in initiating the apical constriction to bend the neural plate

Xenopus

the neural tube closes as the paired neural folds are brought together at the ______

dorsal midline

2 Open Ends of Neural Plate

● Anterior Neuropore ● Posterior Neuropore

Different Neural Tube Defects

Spina Bifida Anencephaly Craniorachischisis

→ failure to close the posterior neuropore around day 27 of development → the severity depends on how much of the spinal cord remains exposed → similar defect this time occurring at the caudal end of the neural tube

Spina Bifida

→ a lethal condition in which failure to close sites 2 and 3 in the rostal neural tube keeps the anterior neuropore open → the forebrain remains in contact with the amniotic fluid and subsequently degenerates → the fetal forebrain ceases development and the vault of the skull fails to form → absence of the major portion of the brain that occurs during embryonic development →a cephalic disorder that results from a neural tube defect occurring when the rostal end of the neural fails to close → typically happens between the 23rd and 26th day of conception

Anencephaly

→ failure of the entire neural tube to close over the entire body axis → neural tube closure is also the result of extrinsic and intrinsic forces

Craniorachischisis

Essential for Neural Tube Formation

● Pax3 ● Sonic hedgehog ● Openbrain genes ● Cholesterol ● Folate

pregnant women are often advised to take supplements of _______ due to the role that foliate binding protein exerts on neural tube closure

folic acid

In secondary neurolation, mesenchyme cells will condense into a ___________ → the central portion of this cord undergoes cavitation to form hollow spaces called ________

medullary cord lumens

Primary vesicles

Prosencephalon Mesencephalon Rhombencephalon

Secondary vesicles

Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon

It will eventually form the cerebral hemispheres

Telencephalon

________ - will form the optic vesicles—the future retina—as well as the thalamic and hypothalamic brain regions, which receive neural input from the retina. The retina itself is a derivative of the diencephalon

Diencephalon

__________ - remains undivided, and its inner space eventually forms the cerebral aqueduct.

Mesencephalon

_________ - The lower part of the brain (myelencephalon) becomes the medulla oblongata, which controls things like feeling pain in the head and neck, hearing, moving the tongue, and regulating heartbeat, breathing, and digestion.

Metencephalon

Two important signaling molecules:

1. Sonic Hedgehog 2. TGF-β protein

_____ is secreted from the notochord and induces the medial hinge point cells to become the ______ of the neural tube.

Sonic Hedgehog floor plate

______ - The dorsal fates of the neural tube are established by proteins of the TGF-p superfamily (BMP4 and BMP7)

TGF-β

The human brain consists of more than _____ neurons associated with over _____ glial cells.

1011 1012

The neuroepithelial cells of the neural tube give rise to three main types of cells.

● ventricular (ependymal) ● precursors of the neurons ● precursors of the glial cells

Important feature of a developing neuron

● Dendrites ● Synapses ● Axon ● Cell body or som ● Neurite

● Within the central nervous system, axons are insulated at intervals by processes that originate from a type of glial cell called an _________. ● The oligodendrocyte wraps itself around the developing axon, then produces a specialized cell membrane called a __________. ● In the peripheral nervous system, myelination is accomplished by a glial cell type called the _________

oligodendrocyte myelin sheath Schwann cell

The _________, the largest part of the brain, plays a pivotal role in cognitive functions and sensory processing. It is responsible for higher-order functions such as perception, memory, language, and decision-making.

cerebrum

The __________ involves intricate processes of cell migration, differential neuronalproliferation, and selective cell death, leading to modifications of the three-zone pattern observed in neural development

cerebellar organization

Cortical neurons are generated from three types of neural precursor cells

• Radial glia cells (RGC) • Short neural precursors (SNP) • Intermediate progenitor cells (IPC)

Development of vertebrate eye process

1. Specification of the Neural Tube 2. Formation of the Eye Field 3. Separation of the Eye Field 4. Formation of the Eye 5. Differentiation of Cells

________: A transcription factor involved in the development of various organs, including the eye

Pax2

_______ , involved in various cellular processes including cell differentiation.

BMP signals

important for the development of melanocytes and pigmented tissues.

MITF (Microphthalmia-associated transcription factor)

critical for eye development and retinal differentiation

Rx gene: (Retinal homeobox gene)

_________: A transcription factor that regulates the expression of genes involved in eye development and patterning.

Otx2 protein

______: A transcription factor essential for eye development, particularly in the formation of the retina and lens.

Pax6

______: A transcription factor involved in eye development, including the specification of retinal neurons.

Six3

If the Sonic hedgehog protein is inhibited, the eye field fails to divide, resulting in _______

cyclopia

The neural tube undergoes complex developmental processes leading to the formation of distinct layers.

Spinal cord and medulla organization

Adjacent cells to the lumen continue to divide, forming a second layer known as the ________.

mantle zone

Neurons in the mantle zone make connections and send axons away from the lumen, creating a cell-poor marginal zone.

Formation of gray and white matter

Retention of Three-Zone Pattern →In the spinal cord and medulla, the three-zone pattern of ______, _____, and ______ persists throughout development.

ventricular, mantle, and marginal layers

The organization of the cerebellum involves intricate processes of ______, ________, and _______, leading to modifications of the three-zone pattern observed in neural development

cell migration, differential neuronal proliferation, and selective cell death

The ________, the ________ plays a crucial role in cognitive functions such as perception, memory, and language. Its formation begins with the intricate orchestration of stem cells and precursor cells within the developing brain.

• neocortex • outer layer of the cerebral hemispheres

Divide at the apical (luminal) surface of the ventricular layer

Radial glia cells (RGC)

They are committed neural precursors

Short neural precursors

They undergo neurogenic divisions, with a small fraction undergoing symmetrical proliferative divisions (dotted circular arrow).

Intermediate progenitor cells

3 types of neural precursorcells

Radial glial cells Short neural precursor Intermediate progenitor cells

Formation of the eye field begins with the specification of the neural tube. The protein _____ induces expression of the gene _____ which allows the specification of forebrain and midbrain on the neural plate.

Noggin Otx2

Once Otx2 proteins accumulate, ____ gene is produced which inhibits further production of Otx2 proteins while activating Pax6 and Six3 genes to form the eye field.

Rx1

• The eye field is separated into two fields due to the secretion of the ________ protein by the prechordal plate. • Neurulation then continues and the eye fields leave depressions on the neural tube called _____. • The optic grooves grow until they reach the surface ectoderm. Once this happens, they become _______ and the surface ectoderm at the point of contact differentiates into the _______.

Sonic hedgehog optic grooves optic vesicles lens placode

If _____ has a loss-of-function mutation, the organism will have small eyes or lack eyes altogether.

Pax6

If the ______ protein is inhibited, the eye field will not separate, resulting in _____, a lethal disorder.

Sonic hedgehog cyclopia

If the Sonic hedgehog protein is overexpressed, the eye will fail to form. This is observed in the cave-dwelling fish _______.

Astyanax mexicanus

______ • is the outer layer of skin • it originates from the ectodermal. -outer layer gives rise to the ______ -inner layer, called the basal layer or stratum germinativum give rise to the ________.

Epidermis periderm true epidermis

Factors that stimulate the development of the epidermis

• BMPs and P63 Transcription Factor • P63 Transcription Factor • Jagged and Notch Pathway

Cutaneous appendages:

Hair Scale Feather

The formation of appendage (hair, scale, feather) equires a series of reciprocal inductive interactions between the dermal mesenchyme and the ectodermal epithelium, resulting in the formation of epidermal thickenings called _____. The epidermal cells have the ability to secrete _______.

placodes Wnt proteins

Determination of the hair follicle versus the epidermal fate. This is done by _______

Wnt signalling

Contributes to the patterning of the distribution of the hair follicles.

Wnt signalling

• Proliferation of epidermal cells results in formation of the _______. • The dermal fibroblasts respond to the ingression of epidermal cells by forming ______. • The hair shaft engulfs the dermal papilla and forms the _______ directly above the papilla.

• Hair follicle placode • dermal papilla • inner hair root

______ →The first hairs in the human embryo. Thin, and closely spaced. ______ → Fine, unpigmented and covers the body of children and adults. ______ → Longer and thicker.

Lanugo Vellus hair U Terminal hair

Hair growth cycle

Anagen Catagen Telogen Return to anagen

It gives rise to the hair shaft, sheath, and sebaceous gland

Multipotent follicular stem cell

gives rise to the pigment of the skin and hair

Melanocyte stem cell

The _____ appears to be a niche that allows cells to retain the quality of "stemness."

bulge

CHAPTER 9 Flashcards

(92 cards)