Chapter 9: The Emergence of Ectoderm

Question 1

Ectoderm forms:

Answer 1

vertebrate nervous system
epidermis

Question 2

3 Major Domains

Answer 2

1. Surface
2. Neural Crest
3. Neural Tube

Question 3

Also known as epidermis; outer layer of skin

Answer 3

Surface

Question 4

the region that connects the neural tube and the epidermis

Answer 4

Neural Crest

Question 5

forms the brain and the spinal cord

Answer 5

Neural Tube

Question 6

Part of the Surface

Answer 6

● epidermis
● hair
● sebaceous glands
● olfactory epithelium
● mouthepithelium
○ anterior pituitary
○ tooth enamel
○ cheek epithelium
● lens and cornea

Question 7

Parts of the Neural Tube

Answer 7

● brain
● neural pituitary
● spinal cord
● motorneurons
● retina

Question 8

It is a structure that serves as the basis for the nervous system

Answer 8

Neural Plate

Question 9

A part of both digestive and respiratory system

Answer 9

Pharynx

Question 10

4 Stages of Pluripotent Development into Neuroblast

Answer 10

Competence
Specification
Commitment
Differentiation

Question 11

parts of Neural crest

Answer 11

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

Question 12

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

Answer 12

Competence

Question 13

→ 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

Answer 13

Specification

Question 14

→ 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

Answer 14

Commitment

Question 15

→ 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

Answer 15

Differentiation

Question 16

2 Ways of Neural Tube Formation

Answer 16

a. Primary Neurulation
b. Secondary Neurulation

Question 17

→ 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

Answer 17

Primary Neurulation

Question 18

→ 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

Answer 18

Secondary Neurulation

Question 19

3 Sets of Cells in Ectoderm

Answer 19

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

Question 20

forms when the edges of neural plate thicken and move upward

Answer 20

Neural folds

Question 21

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

Answer 21

Neural groove

Question 22

4 Stages of Neurulation

Answer 22

1. Formation and folding of the neural tube
2. Shaping and elevation of the neural tube
3. Convergence of the neural folds, creating a neural groove
4. Closure of the neural groove to form the neural tube

Question 23

important factor in shaping the neural plate

Answer 23

epidermis

Question 24

→ shaped by the movements of the epidermal and neural plate regions

→neural plate lengthens along the anterior-posterior axis and narrows by convergent extension

→convergence and extension movements are
critical for shaping the neural plate

→in chick, divisions of the neural plate cells
are in the anterior-posterior, or break-tail,
direction

Answer 24

Formation and Shaping of Neural Plate

Question 25

→bending of the neural plate involves the formation of hinge regions where the neural plate contacts surrounding tissue

Answer 25

Bending and Convergence of Neural Plate

Question 26

in birds and mammals, the cells at the
midline of the neural plate forms the

Answer 26

medial hinge point (MHP)

Question 27

→Primary Neurulation is regulated by two forces:

Answer 27

1. Intrinsic wedging
2. Extrinsic forces

Question 28

occurs within cells of the hinge regions, bending the neural plate

Answer 28

Intrinsic wedging

Question 29

the migration of the surface ectoderm
toward the center of the embryo

Answer 29

Extrinsic forces