Development

Question 1

____ occurs in ampullary region of fallopian tube 12-24 hours after ovulation

Answer 1

fertilization

Question 2

At about __ hrs. the fertilized cell divides into a 2 cell stage.

Answer 2

30

Question 3

A second cleavage occurs around __ hrs. creating a 4 cell zygote.

Answer 3

40

Question 4

After the 16 cell or morula stage is reached (3 days) the zygote evolves into an ____ cell mass and an ____ cell mass and is called a ____ (5 days).

Answer 4

inner
outer
blastocyst

Question 5

____ of the blastocyst in the uterine wall occurs on day 6.

Answer 5

Implantation

Question 6

The ____ (which forms the yolk sac and primitive gut) and the ____ are formed by the end of the 2nd week.

Answer 6

endoderm

ectoderm

Question 7

A layer of ____ cells is visible between the ectoderm and endoderm during the 3rd week of development

Answer 7

mesodermal

Question 8

5 stages of Nervous System Development:

Answer 8

1. Neurulation
2. Cellular Proliferation
3. Neuronal Migration
4. Cytodifferentiation and Axonal Elongation
5. Maturation of synaptic contacts and Refinement

Question 9

Layers of the trilaminar embryo:

Answer 9

1. Endoderm (differentiates into viscera)
2. Mesoderm (differentiates into the heart and circulatory system, muscle, bone and meninges. Also forms somites and the notochord)
3. Ectoderm (differentiates into the CNS structures, adrenal medulla and skin)

Question 10

5 steps in progressive formation of CNS structures from embryonic ectoderm.

Answer 10

1. Ectoderm thickens to form the neural plate.
2. Neural groove
3. neural folds
4. neural tube forms a closed tubular structure. (the rostral portion should close by day 27 while the caudal portion should close by day 30)
5. Neural crest forms sensory ganglia of spinal and cranial nerves.

Question 11

How do divisions of the brain differ in embryo’s vs. adults?

Answer 11

Embryonic brain (3-4 weeks) has 3 components
Adult brain (5 weeks and beyond) has 5 major areas.

Question 12

failure of rostral neuropore to close; much of cerebral hemisphere is absent.

Answer 12

Anencephaly

Question 13

Falure of caudal neuropore to close.

Answer 13

Spina bifida

Question 14

3 main categories of spin bifid a are:

Answer 14

Spina bifida oculta (one or more vertebrae are malformed)
Spina bifida with meningocele (meninges protrude in a saclike cavity on the back)
Spina bifid a with myelomeningocele (spinal cord and meninges protrude in a saclike cavity on the back over the defect.

Question 15

Part of the cerebellum and caudal brainstem herniate through foramen magnum, obstructing flow of CSF and producing hydrocephalus.

Answer 15

Arnold-Chiari malformation

Question 16

Tissue of the neural plate and neural tube can be divided into 3 layers. They are:

Answer 16

Germinal Zone (Ventricular Zone)
Intermediate Zone
Marginal Zone (also the cortical plate)

Question 17

The innermost layer of the neural plate consisting of pluripotent neuroepithelial cells.

Answer 17

Germinal zone

Question 18

Newly divided cells in the germinal layer can be classified as ___ and ____. The ___ then use the ____ to help them migrate out of the germinal zone.

Answer 18

Neuroblasts and glioblasts

Neuroblasts use the glioblasts

Question 19

The process where neuroblasts leave the germinal zone to the outer brain layers is called

Answer 19

Radial migration

Question 20

In radial migration, glial cells secrete ____ to help neurons find the correct pathway.

Answer 20

chemical attractants

Question 21

Neurons have ____ on their surface that enable them to bind to glial cell fibers.

Answer 21

adhesion molecules

Question 22

Many factors including ____, ____, and ____ can interfere with the process of neuron migration.

Answer 22

radiation, genetic mutation, and drugs such as cocaine and alcohol.

Question 23

3 main points in formation of spinal cord are:

Answer 23

1. Sulcus limitans separates dorsal from ventral neurons
2. Alar plate is the dorsal, sensory and association region
3. Basal plate is the ventral, motor region

Question 24

3 steps in axon elongation:

Answer 24

1. Growth cone (enlargement on the distal end of a growing axon, has filapodia and lamellipodia)
2. Pathfinding (through contact repulsion, chemo repulsion, contact attraction, contact repulsion) usually involving receptor and lingand interactions
3. Synapse formation

Question 25

Since the body produces more axons/synapses than needed, pruning must take place. The mechanism involves ____, ____, and ____.

Answer 25

activity, neurotrophic factors, and intrinsic genetic programs