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29 Cards in this Set

  • Front
  • Back
What are germ cells derived from?
What is role of notochord and how is it formed?
epiblast
role notochord-
a. primary inductor in early embryo
b. induces overlying ectoderm to form neural plate->tube
Formed from migrating cells that formed a median columb of cells
What does the ectoderm form?.
Ectoderm-
Epidermis structures such as
a. skin, nails, hair
b. neural crest and neural cells (i.e. nervous system)
What does the endoderm layer form?
epithelium of
a. digestive and respiratory system
b. liver and pancreas
What does the mesoderm layer form?
a. somites- form muscle cartilage of the ribs, vertebrae and dermis of notochord,
b. blood, blood vessels and connective tissue
During neuralization what structures will the neural tube give rise to?
CNS (brain, spinal cord) retina, pineal body, posterior pituitary

- originated from ectoderm
1.Explain why weeks 3-8 ("embryonic period") are a critical period in human development.
-Maximum susceptibility to abnormal development
a. all major body systems developed
b. folding embryo-craniocaudal folding
c. formation of umbilical cord
d. Hox genes control segmentation
2.List and describe the development of the three main components of the head mesoderm.
1. Segmented- myotomes of head somites give rise to skeletal muscle
2. Unsegmented- head mesenchyme of the first 7 somitomeres, gives rise to the neurocranium and upper face
3. Branchial/ Pharyngeal Arch Mesoder- forms neuromeres, rhombomeres
What is the role of induction in any period of development?
What are main inducer groups during Embryonic period and briefly describe (2)?
Induction is when one group of cells/tissues causes antoher set or cells/ tissues to change their fate.
a. GDFs (Growth and Differentiation factors)- proteins that diffuse short distances
b. CAMS (Cellular adhesion molecules)- transmembrane proteins that ensures cells with tissues remain bound together
What are the 4 general catagories of GDFs?
Briefly describe each...
1. FGFs- fibroblast growth factors- 2 dozens, 100s of isoforms, important for angiogenesis, axon growth, and mesoderm differentiation
2. WNT proteins (15)- limb patterning, some aspects of brain, somite and urogenital differentiation.
3. Hedgehog proteins- involved in neural tube induction/patterning, limb patterning and somite differentiation
3 types
i. Desert
ii. Indian
iii. Sonic
4. (Transforming growth factor- B superfamily)- TGFB's, activins, bone morphogenetic proteins (BMPs). BMPs induce bone formation and regulate cells division, apoptosis, and cellular migration
The following congenital malformations are caused by defects or lack of what specific genes? Briefly describe physical presentations...
a. tooth angenesis
b. Wilm's Tumor-
c. Anonychia
a. Axin2- missing teeth in places they should be
b. WXT- common kidney tumors in children
c. RSP04- no toe nails
What are the disorders and what protein misfire causes them?
a. Wilms tumor- WXT
b. Autosomal recessive anonychia- RSP04
c. Tetra- amelia- WNT3
What is role of BMP-4 in neurulation?
What is its relation to the signaling molecules from the mesoderm?
BMP-4 act as inhibitors of neural formation. Found in abundance in ectoderm.
- signaling molecules block BMP-4 inhibitory action
What happens if BMP-4 is blocked? What happens if BMP-4 is present?
What kind of implications does this have for mutants without BMP-4?
if blocked- ectoderm forms neural plate
if present- ectoderm becomes epidermis

Mutants would have their neural tissue made as default and not develop epidermis cells
What is the major axial signaling center of the trunk and what is "head organizer"
a. notochord
b. Prechordal plate= head organizer
What are the divisions of the Ectodermal layer and what do they differentiate into?
1. neuroectoderm- Brain, spinal cord = CNS
2. Neural Crest- PNS, melanocytes, cells of the adrenal medulla
3. Surface ectoderm- epithelial ectoderm
From this step "Thickening of neural plate.. what happens next?
1. formation of neural folds and groove
2. Convergence of the lateral margins of the neural plate
3. Fusion of neural plate to form the neural tube
This picture is as follows what are arrows pointing to?
a. Surface ectoderm
b. Roof plate
c. Neural crest
d. neural tube
e. floor plate
How do neurons differentiate into sensory vs. motor neurons?
Explain basic genes involved and role of concentration gradient...
It depends on signaling molecule and from ability of Hox gene neurons can sense relative concentration of BMP-4 gene vs Sonic hedge hog (Shh).
If concentration on axis is great Shh neuron will differentiate to motor neuron
If concentration is greater BMP-4 it will become sensory neuron
What is an example of a regulator of expression of Hox gene?
What are examples of when regulators pose problems?
Retinoic Acid (RA)- necessary for normal development. Derivatives are found in many products (accutane, rogaine)...
Changes concentration gradients which causes messed up regulation of Hox gene and abnormalities
Explain how this happens what is this called?
This is called Rachischisis from a neural tube defect. Specifically failure of neural tube to close
What causes this and what is it called?
failure of closure of cranial neuropore
called... Anencephaly
Neural tubes closure occurs in 5 waves in normal embryogenesis as pictured below...
What is the name of problem and details if there are failures in
a. wave 2
b. waves 4 and 5
c. Wave 5
a. anencephaly- failure in cranial closure, small head
b. myelomeningocele- cranial defect with herniation of intracranial contents, most common in occipital region
c. Spina bifida- failure of caudal closure... 4 different kinds 3/4 have spinal cyst
Describe secondary neurulation and explain why it does not have as great importance for humans...
Takes place caudul to posterior neuropore (no tails in human so not too important)
Problems arising from it are called myelodysplasias
Define myelodysplasias and describe some...
Malformations from secondary neurolation
1. hair growth in spots
2. telangiectasias (large superficial capillaries)
3. Coccygeal pits- dimples on butt
4. Tethered Cord- syndrome
What does current research show causes Neural Tube defects (NTDs)?
Dietary and Genetics are main but...
1. often a link in transformation of homocysteine to methionine
2.increased homocysteine prevents closure
What may prevent NTDs? How?
How do we test for NTDs?
1. folic acid- unclear how?
1. AFP- (alpha-fetoprotein) testing in Mom's blood serum- AFP is produced in fetal liver and leaks across defect into amniotic fluid and across placenta into maternal serum.
What is the cause of the following disorders?
a. piebaldism
b. vitiligo
c. ectodermal dysplasia (ED) syndromes
a. diesase of melanocyte formation, characterized by congenital white forelock
- Characterized by loss of melanocytes- autoimmune- splotches on skin
c. 150 heritable disorders affecting ectoderm usually from two types of features
What is tethered cord syndrome?

What could happen from it?
during neural cord formation
conus medullaris (end of spinal cord) and filum terminale abnormally attach to the wall of the spinal column

rubbing or pressure on lower body region causes irritation and nerve damage to body