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Transcript
Now we focus on individual lineages
Chapter 12- CNS and epidermis
Recall lineages:
__________________-skin/nerves
___________-Blood, heart, kidney, bones
___________- Gut and associated organs
Ectoderm has three fates
1._________
2. _________ cells
3. _________ tube
Fig. 12.3
Epidermis (skin)
Peripheral neurons,
facial cartilage
Brain and spinal chord
This process is called _____________
Dorsal ectoderm becomes neural 1. _______
_______ to become neural
Neurulation
_____to become neural _____
a. _______
Two types of neurulation
1. ________- “pinching off”
2. _______ – hollow out a cord
b. _______
____ are used in many creatures
Neural plate
Neural crest
epidermis
c. __________
d. _________
Fig. 12.4- Amphibian embryo
Neural tube
Fig. 12.3
A few details at each step in primary neurulation
a. _________
Mesoderm signals ectodermal cells to form neural plate
b. ________ and c. _____________
•Mesoderm signals ectodermal cells to form neural plate
•Hinge cells (called medial hinge point cells) attached to notochord
•Cell shape and cells movement contribute to elevation
Fig. 12.6
d. _______- Folds adhere to each other
Failure of complete closure results in
neural tube defects
•__________ – anterior tube fails to
closebrain development ceases
•___________ – posterior tube fails to
close at human day 27
• ___ of spina bifida preventable with 0.4mg/day vitamin B12
2. _________ neurulation
A cord is first made, then ________ out
Example- posterior end of chick
Note- rest of chick uses _________ neurulation
Further neural tube differentiation
1. _____________________axis
Anterior portion of neural tube forms three _______:
1. __________
2. _________
3. _________
Brain volume increases ________
between days 3 and 5 of
development
Brain development is complex and laden with nomenclature
Fig. 12.10- human brain development
2. Dorsal-ventral axis
Fig. 12.13- chick neural tube
Epidermis (then roof plate) secretes ______
family proteins (BMP-4 and –7, dorsalin,
activin) to signal dorsal portion of neural
tube to become _____________
Notochord (then hinge cells) secretes ______
_________to signal ventral portion of neural
tube to become motor neurons
•Retinoic acid also plays a role
Roof plate
Hinge cells
Neuronal types
• Brains consists of 1011 ________ (nerve cells) and 1012 ______ (support cells)
• The long-held belief that neurons were fully determined at birth
is incorrect•Evidence for neuronal stem cells exists
Cells lining neural tube can give rise to _______ or _____ cells
Fig. 12.22- A motor neuron
Input axons from other neurons Growth
cone
Axon
•At birth, very few dendrites are
present on cortical neurons
• Cortical neurons connect to
________ other neural cells
during 1st year post birth!!
________- connect to other neurons
• ______ are part of the cell body that can extend several feet
• ___________ explores and moves into new regions of body
Nerve cells are protected to facilitate ________ signal conduction by:
In ________ nervous system
In ________ nervous system
By ______ _______ produced
by oligodendrocytes
By myelination
from _______ ____
Pax gene expression
Vertebrate eye development
Pax6 gene encodes protein that directs eye development
Neural-tube specific enhancer
Recall chapter 5- Fig. 5.15-the Pax 6 gene
Recall chapter 5- introduce
DNA containing pax6 cDNA
under control of an
inducible promoter + a
tissue-specific enhancer
Fig. 5.14
Observe additional eyes
Pax6 mutants lack eyes in __________________
_____________ dictates formation of two eyes
•Mutants produce one eye (cyclopia)
Fig. 6.25- a
cyclopic lamb
Eye development requires the
specification of numerous tissues
Eye lens development forms by:
1. Lens vessicle ______ onto itself to form ring
2. Interior cells
______________
______ to produce
crystallin lens fibers
Fig. 12.27
Fig. 12.29
3. Cells _________
A few words about epidermis (skin) development
Recall:
1.Epidermis
2.Neural crest cells
3.Neural tube
Epidermis (skin)
Peripheral neurons,
facial cartilage
Brain and spinal chord
Epidermis becomes two layers, a ___________ (which
is shed) and a __________ that gives rise to _____ cells
(Shed)
________
Epidermis
Basal layer
Granular cells Keratinocytes
Spinous layer
Termed “_________________”
Fig. 13.32
Keratinocytes (continually shed)
TGF-a and FGF7 are
important factors in
skin development
_______ layer
_______ layer
________ layer
_______ layer
Cells
__________
and migrate
toward surface
Feather, hair and scales are
formed by epithelialmesenchymal interactions
between epidermis and
mesoderm