Chapter 13 Flashcards
What are the 3 different major cell lineages that the ectoderm forms?
1) Surface ectoderm
2) neural crest
3) Neural tube
What does the surface ectoderm form?
primary epidermis
What does the neural crest form? (4)
1) Peripheral neurons
2) neural support cells
3) pigmentation cells
4) dentine (of teeth)
What does the neural tube form?
brain (anterior) and spinal chord (posterior)
_______: the differentiation of the ectoderm into neural tissues and structures
neurulation
_______: region of specified ectoderm that will take on new features
neural ectoderm
Folding of the neural plate forms the _______ which is the beginning of the nervous system
neural tube
When the embryo has the neural tube it is called a _______
neurula
Cells involved in neurulation are called _______
neuroblasts
_______: surrounding cells direct the neural plate to invaginate and pinch off from the remaining ectoderm as a hollow tube
primary neurulation
_______: mesenchyme cells form a solid cord that then cavitates to form a hollow tube
secondary neurulation
_______ mesenchyme cells are responsible for secondary neurulation
coalescing
What are the 4 steps to 1° neurulation?
1) _______ of the neural plate
2) _______ of the neural plate
3) _______ of the plate into the neural groove
4) _______ of the neural groove and neural tube
1) formation
2) elongation
3) shaping
4) closure
Formation of the neural tube:
- mesoderm signals overlying ectoderm to elongate into _______ neural plate cells
columnar
Elongation of the neural plate:
- elongates in the _______ direction
- elongation driven by _______ preferentially aligned along the _______ axis extending the neural plate
anterior/posterior
cell divisions
A/P
Shaping of the plate into the neural groove:
what are the two hinges formed during this step?
1) Medial hinge point (MHP)
2) Dorsolateral Hinge point (DLHPs)
The medial hinge point forms in the center of the _______
neural plate
The dorsolateral hinge points form at the connections between neural and the remaining ectodermal cells called the _______
neural folds
Closure of the neural groove and neural tube:
cells change from _______ to _______ expression, and in many species, some of the cells at the junction migrate away as _______
E-cadherin to N-cadherin
neural crest cells
- mesenchymal cells that will form other tissues
What are the names of the locations where the neural tube closes?
anterior neuropore
posterior neuropore
_________: closure failure of the posterior end
- spinal cord open and can be corrected by in-utero surgery
spina bifida
_______: closure failure at the anterior end
- brain/skull malformations, generally fatal
anencephaly
Neural tube defects in 1 out of every_____ live human births
- mainly due to insufficient dietary _______
1000
folic acid (B9)
Mutations in genes can lead to neural tube defects. What are some of these genes? (5)
1) Pax3
2) SHH
3) Grainy head
4) Fap2
5) open brain
What environmental factors can lead to Neural tube defects?
deficiencies in:
1) cholesterol
2) zinc
3) folic acid
Presence of:
1) diabetes
2) obesity
While the posterior end of the tube is still forming, the anterior end begins to bulge and dramatically change in shape forming _________
3 primary vesicles
By the time the posterior end closes, the _______ have begun to form
5 secondary vesicles
(primary)
_______: forms the cerebral hemispheres
Prosencephalon
(primary)
________: neurons involved in motivation, movement, and depression
mesencephalon
(primary)
________: cerebellum, pons, medulla oblongata
- involved in involuntary breathing
Rhombencephalon
________ divides the hindbrain into smaller compartments
rhombomeres
Neural tube axis polarization:
_______, where spinal neurons receive input from sensory neurons
dorsal
Neural tube axis polarization:
_______, where interneurons relay information between sensory neurons and motor neurons
middle
Neural tube axis polarization:
_______, where motor neurons predominate
ventral
Homeobox genes _______ and _______ are in charge of dorsal domain
Pax3
Pax7
- these are TF’s
Homeobox genes _______ are in charge of middle domain
Pax6
Homeobox genes _______ are in charge of ventral domain
Nkx6-1
Morphogenic signals from its environment induce the D/V polarity of the neural tube. In the spinal region, ventral is imposed by the _______, and dorsal is imposed by the overlying _______
notochord
epidermis
Paracrine factors from the ectoderm and notochord induce secondary production centers in the Neural Tube itself:
- Floor plate/Notochord produces: _______
- Roof plate/dorsal ectoderm produces: _______
SHH
BMP4
The ultimate identity of the gene expression pattern in each set of cells in the neural tube is dependent on:
1) its _______ from the morphogenic signaling center
2) the _______ of the received signal
distance
duration
