Chapter 9- Reporting Flashcards
These cells are develop to form the vertebrate nervous system as well as the epidermis of an organism
ectoderm
three major domains of ectoderm
surface, neural crest, and neural tube
→ is also known as the epidermis
→ the outer layer of our skin
surface
→ the region that connects the neural tube and the epidermis
neural crest
→ forms the brain and the spinal cord
neural tube
what are the parts of the surface of ectoderm
● epidermis
● hair
● sebaceous glands
● olfactory epithelium
● mouth epithelium
● lens and cornea
parts of the neural crest
● peripheral nervous system
● adrenal medulla
● melanocytes
● facial cartilage
● dentine of teeth
what does peripheral nervous system composed of?
○ schwann cells
○ neuroglial cells
○ sympathetic nervous system
○ parasympathetic nervous system
parts of the neural tube
● brain
● neural pituitary
● spinal cord
● motor neurons
● retina
→ it is a structure that serves as the basis for
the nervous system
neural plate
is a flexible rod-shape found in embryos of
all chordates composed of mesodermal cells
notochord
→ a part of both digestive and respiratory system
pharynx
4 Stages of Pluripotent Development into
Neuroblast
competence
specification
commitment
differentiation
→ multipotent cells become neuroblast once they are exposed to the appropriate signals
→ have the ability to response to the particular signal
competence
→ the cells received the signals and successfully develop into neuroblasts, but… progression along the neural differentiation pathway repressed by other signal
→ which means, it is a transition between cells to become anything with their own fates
specification
→ 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
→ 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
2 Ways of Neural Tube Formation
primary neurulation and secondary neurulation
→ 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
→ the neural tube arises from the coalescence of mesenchyme cells 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
3 Sets of Cells in Ectoderm
● the internally positioned neural tube
● the externally positioned epidermis of the skin
● the neural crest
forms when the edges of neural plate
thicken and move upward
neural folds
appears in the center of the plate,
dividing the future right and left sides of the embryo
neural groove
4 Stages of Neurulation
- Formation and folding of the neural tube
- Shaping and elevation of the neural tube
- Convergence of the neural folds, creating a
neural groove - Closure of the neural groove to form the neural tube
important factor in shaping the
neural plate
epidermis
in birds and mammals, the cells at the
midline of the neural plate forms the ______________________
medial hinge point (MHP)
Primary Neurulation is regulated by two forces:
intrinsic wedging and extrinsic forces
→ occurs within cells of the hinge regions,
bending the neural plate
intrinsic wedging
→ the migration of the surface ectoderm
toward the center of the embryo
extrinsic forces
anchored to
the surface ectoderm, and increase their height and
become wedge-shaped
dorsolateral hinge points
this is intimately linked to
changes in cell shape
cell wedging
- an inhibitor of
microtubule polymerization - inhibits the elongation of these
cells
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
2 Open Ends of Neural Plate
anterior and posterior neuropore
→ 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
- important in mediating neural tube
closure
→ pregnant women are often advised to take
supplements of folic acid due to the role that
foliate binding protein exerts on neural tube
closure
folate
→ the central portion of this cord undergoes
cavitation to form hollow spaces called ___________
lumens
the neural tube and its lumen
bulge and constrict to form the chambers of the brain and
spinal cord.
gross anatomy level
the cell populations in the wall of the neural
tube rearrange themselves to form the different functional
regions of the brain and spinal cord.
tissue level
The neuroepithelial cells transform into
the various nerve cells (neurons) and supportive cells (glia)
found in the body
cellular level
Primary vesicles of anterior- posterior axis
prosencephalon (forebrain), mesencephalon (midbrain) and Rhombencephalon (hindbrain)
subdivided into the anterior
telencephalon and the more caudal
diencephalon
prosencephalon
subdivided into the anterior
telencephalon and the more caudal diencephalon
mesencephalon
subdivided into the anterior
telencephalon and the more caudal
diencephalon
rhombencephalon
Secondary vesicles of anterior- posterior axis
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
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 is its derivative
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
becomes the cerebellum,
which helps coordinate movement,
balance, and posture
myelencephalon
The top-bottom differences in the neural tube are caused by signals around it. The _______________ is influenced by the notochord below it, while the _______________ is influenced by the skin above it.
ventral side, dorsal side
Two important signaling molecules in dorsal-ventral axis
- Sonic Hedgehog
- TGF-β protein
is secreted from the notochord and induces the medial hinge point cells to become the floor plate of the neural tube
sonic hedgehog
The dorsal fates of the neural tube are
established by proteins of the TGF-p superfamily (BMP4 and BMP7)
TGF-β
The fate of the _________part of the neural
tube is decided by certain proteins, like
BMPs 4 and 7, dorsalin, and activin, which
are part of a family called TGF-β
dorsal
In the ___________ part of the neural tube, there’s
a gradient of Sonic hedgehog which
determines what kind of cells form based
on how much of it they get
ventral
3 main types of the cells in brain
● 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 sys- tem, axons are
insulated at intervals by processes that originate from a type of glial cell called an _______________
oligodendrocyte
The oligodendrocyte wraps itself around the
developing axon, then produces a specialized
cell membrane called a ___________
myelin sheath
In the peripheral nervous system, myeli- nation is accomplished by a glial cell type called the
Schwann cell
are specialized for secreting specific chemical
neurotransmitters across the small gap (the synaptic cleft) that separates the axon of a neuron from the surface of its target cell.
axon
comprises neurons
organized into layers (cortices) and clusters (nuclei), each
with specific functions and connections.
CNS
a layer of rapidly dividing neural stem
cells.
neuroepithelium
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
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 outer layer of the cerebral
hemispheres, 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
→ Divide at the apical (luminal) surface of the
ventricular layer
radial glia cells
they are committed neural precursors
short neural precursor
they undergo neurogenic divisions, with a small fraction undergoing symmetrical proliferative divisions (dotted circular arrow).
intermediate progenitor cells
three types of neural precursor cells
- Radial glia cells
- short neural precursors
- intermediate progenitor cells
It accumulate as the eye field becomes
specified
Otx2
Neurulation continues as usual which causes the eye field to fold into the neural tube, leaving ____________ ____________
optic grooves
The optic grooves grow into the surface ectoderm, becoming ________________ in the process
optic vesicles
The point of contact of the optic vesicle and surface ectoderm forms the ______________which will soon form the retina
lens placode
A transcription factor involved in the
development of various organs, including the eye.
Pax2
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
The retina contains ________________, maintaining its integrity, as well as ________________ and horizontal neurons, which transmit impulses within the retina
muller glial cells, amacrine neurons
are proteins found abundantly
in the lens of the eye, contributing to its transparency and
refractive properties
crystallins
If Pax6 has a loss-of-function mutation, the
organism will have ____________________________
small eyes or no eyes at all
If the Sonic hedgehog protein is inhibited, the eye field fails to divide, resulting in __________
cyclopia
If the Sonic hedgehog protein is overexpressed, the
eyes ________________
fail to form
● It is the outer layer of skin
● Originates from the ectodermal (* cells
covering the embryo after neurulation.)
epidermis
gives rise to the periderm
outer layer
give rise to the true epidermis
basal layer or stratum germinativum
The basal layer divides to produce an
outer population of cells that constitute
the spinous layer. Together, these two
layers are referred to as the ______________
malpighian layer
Cells of the Malpighian layer further
divide to produce the ______________of
the epidermis. Cells in this layer
contain granules of the protein keratin.
granular layer
Cells in the granular layer begin to
differentiate into epidermal skin cells
called
keratinocytes
As keratinocytes mature, they migrate
outward and form the _______________________. These cells become
flattened sacs of keratin protein, with
their nuclei pushed to one edge of the
cell
cornified layer (stratum corneum)
derived from the neural
crest, reside in the Malpighian layer.
They transfer pigment sacs
(melanosomes) to developing
keratinocytes, contributing to skin
pigmentation.
melanocyte
Factors that Stimulate Development of the
Epidermis
- BMPs and p63 transcription factors
- p63 transcription factor
- jagged and notch pathway
- It regulates keratinocyte proliferation
and differentiation.
p63
what are the cutaneous appendages?
hair, scale, feather
what do you call the epidermal thickening?
placodes
This signaling mechanism determines the fate of the cells if they will be a hair follicle or an
epidermal cell.
Wnt signaling
The dermal fibroblasts
respond to the ingression of
epidermal cells by forming
___________________
dermal papilla
The papilla signals the
proliferation of the hair
germ, making it into a
primitive _________________
hair shaft (hair peg)
what are the types of hair?
lanugo, vellus, and terminal hair
→ The first hairs in the human embryo. Thin, and closely spaced
lanugo
→ Fine, unpigmented and covers the body of
children and adults.
vellus hair
type of hair that is longer and thicker.
terminal hair
is one structure that mammals are able to
regenerate
hair
● The first phase is the _________ where the hair grows, there is a blood supply that nourishes the hair follicle that enables it to grow.
● The second phase is the _________, where the hair lost its blood supply, so it stopped growing.
● The third phase is the ___________, where the hair dies and falls off eventually.
● And then it will return to ____________, a new hair will grow
anagen, catagen, telogen, anagen
he drew the histology of the
human hair, he believed that the “bulge” is the
attachment area for the arrector pili.
Phillipp Stohr
It gives rise to the hair shaft, sheath, and
sebaceous gland,
multipotent follicular stem cell
It gives rise to
the pigment of the skin and hair
melanocyte stem cell
The bulge appears to be a niche that allows
cells to retain the quality of “_________-.”
stemness
