Body Plan Development

Question 1

The sclerotome arises from cells that were located in the:

a. notochord
b. paraxial mesoderm
c. intermediate mesoderm
d. lateral plate mesoderm
e. none of the above

Answer 1

b. paraxial mesoderm

Question 2

The cardiogenic plate arises from:

a. embryonic endoderm
b. somatic mesoderm
c. splanchnic mesoderm
d. intermediate mesoderm
e. neural crest

Answer 2

c. splanchnic mesoderm

Question 3

An inductive stimulus from which structure stimulates the transformation of the epithelial sclerotome into secondary mesenchyme?

a. neural crest
b. somite
c. ectodermal placodes
d. embryonic endoderm
e. notochord

Answer 3

e. notochord

Question 4

Which of these structures in the embryo is unsegmented?

a. somitomeres
b. neuromeres
c. notochord
d. somites

Answer 4

c. notochord

Question 5

The intermediate mesoderm is the precursor of the:

a. urogenital system
b. heart
c. somites
d. body wall
e. vertebral bodies

Answer 5

a. urogenital system

Question 6

What forces are involved in the folding of the neural plate to form the neural tube?

Answer 6

A change in cell shape at the median hinge point and pressures of the lateral ectoderm acting to push up the lateral walls of the neural plate.

Question 7

What role do neuromeres play in the formation of the central nervous system?

Answer 7

Neuromeres provide the fundamental organization of parts of the brain in which they are present. Certain homeobox genes are expressed in a definite sequence along the neuromeres.

Question 8

From what structures do the cells that form skeletal muscles arise?

Answer 8

The somites. Axial muscles formed from cells derived from the medial halves of somites, and limb muscles arise form cellular precursors located in the lateral halves of somites.

Question 9

Where do the first blood cells of the embryo form?

Answer 9

In blood islands that arise from mesoderm of the wall of the yolk sac.