Chapter 5

Question 1

Chest xray shows dextrocardia, what other clinic identifies complete situs inversus?
A. Urology
B. Derm
C. Infertility
D. Orthopedic 
E. Oncology

Answer 1

Because of the respiratory problems associated with
his situs inversus, this man probably has a mutation
of a dynein gene. Commonly, such individuals also have
immotile spermatozoa, a condition that would lead to
infertility.

Question 2

The principal inductor in primary neural induction is the:
A. Hypoblast 
B. Primitive streak
C. Extraembryonic mesoderm
D. Notochodral process 
E. Embryonic ectoderm

Answer 2

D. Notochodral process

Question 3

Which of the following tissues arises from cells passing thru the primitive streak?
A. Embryonic endoderm
B. Hypoblast 
C. Cytotrophoblast 
D. Primary yolk sac 
E. Amnion

Answer 3

A. Embryonic endoderm

Question 4

Cells of which germ layer are not present in the oropharyngeal membrane?
A. Ectoderm
B. Mesoderm
C. Endoderm
D. All are present

Answer 4

B. Mesoderm

Question 5

The prechordal plate plays an important role in regionalization of the:
A. Notochord
B. Forebrain
C. Embryonic mesoderm
D. Primitive node 
E. Hindbrain

Answer 5

B. Forebrain

Question 6

Brachyury, a deficiency in caudal tissues in the body, is caused by a mutation in what gene?
A. Lim-1
B. Noggin
C. T
D. Sonic hedgehog
E. Activin

Answer 6

C. T

Question 7

Which layer of the bilaminar (two-layered) embryo gives rise to all of the embryonic tissue proper?

Answer 7

The epiblast.

Question 8

Of what importance is the primitive node in embryonic development?

Answer 8

The primitive node acts as the organizer of the embryo.
Through it pass the cells that become the notochord. The
notochord induces the formation of the nervous system.
The primitive node is also the site of synthesis of
morphogenetically active molecules, such as retinoic acid.
If a primitive node is transplanted to another embryo, it
stimulates the formation of another embryonic axis.

Question 9

The migration of mesodermal cells from the primitive streak is facilitated by the presence of what molecules of the extracellular matrix?

Answer 9

Hyaluronic acid and fibronectin.

Question 10

What molecules can bring about mesodermal induction in an early embryo?

Answer 10

Vg1 and activin.

Question 11

At what stage in the life history of many cells are cell adhesion molecules lost?

Answer 11

Cell adhesion molecules are lost in a migratory phase.
When the migratory cells settle down, they may
re-express cell adhesion molecules.