1. Chapter 12- CNS and epidermis
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
Epidermis (skin)
1._________
Peripheral neurons,
facial cartilage
2. _________ cells
3. _________ tube
Brain and spinal chord
Fig. 12.3
This process is called _____________

2. Two types of neurulation ________- “pinching off”
Dorsal ectoderm becomes neural _______ to become neural _____to become neural _____
1. _______
Neurulation
Neural plate
Neural crest
a. _______
epidermis
Two types of neurulation
________- “pinching off”
_______ – hollow out a cord
____ are used in many creatures
b. _______
c. __________
d. _________
Fig Amphibian embryo
Neural tube
Fig. 12.3

3. A few details at each step in primary neurulation
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 close-
brain development ceases
___________ – posterior tube fails to
close at human day 27
___ of spina bifida preventable with 0.4mg/day vitamin B12

4. Brain volume increases ________ between days 3 and 5 of development
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

5. Brain development is complex and laden with nomenclature
Fig human brain development

6. Retinoic acid also plays a role
2. Dorsal-ventral axis
Fig 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

7. Cells lining neural tube can give rise to _______ or _____ 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 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

8. Nerve cells are protected to facilitate ________ signal conduction by:
In ________ nervous system
In ________ nervous system
By myelination from _______ ____
By ______ _______ produced by oligodendrocytes
Pax gene expression
Vertebrate eye development
Pax6 gene encodes protein that directs eye development
Neural-tube specific enhancer
Recall chapter 5- Fig the Pax 6 gene

9. Observe additional eyes
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 a cyclopic lamb

10. Eye development requires the specification of numerous tissues
Eye lens development forms by:
1. Lens vessicle ______ onto itself to form ring
Fig
2. Interior cells ______________ ______ to produce crystallin lens fibers
3. Cells _________
Fig

11. A few words about epidermis (skin) development
Recall:
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 “_________________”

12. Keratinocytes (continually shed)
Fig
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 epithelial-mesenchymal interactions between epidermis and mesoderm