28. Human Development

Which of the following is a benefit of cells getting smaller as cleavage occurs?

A hollow ball of cells created by cleavage is called a(n)?

Indicate whether each of the following statements is describing (a) cleavage or (b) gastrulation.

_______ (1) period during which a morula forms

_______ (2) period when vast amounts of cell migration occur

_______ (3) period when the three embryonic germ layers appear

_______ (4) period during which the blastocyst is formed

The outer layer of the blastocyst, which later attaches to the uterus, is the

(a) decidua

(b) trophoblast

(c) amnion

(d) embryoblast

Match each adult structure in column B with the embryonic structure it derives from in column A.

Column A

_______ (1) notochord

_______ (2) ectoderm (not neural tube)

_______ (3) intermediate mesoderm

_______ (4) lateral plate mesoderm

_______ (5) sclerotome

_______ (6) coelom

_______ (7) neural tube

_______ (8) endoderm

Column B

(a) kidney

(b) peritoneal cavity

(c) pancreas, liver

(d) parietal serosa, most tissues of limbs

(e) nucleus pulposus

(f) hair and epidermis

(g) brain

(h) ribs and vertebrae

The germ layer from which the epidermis and brain are derived is the

(a) ectoderm

(b) endoderm

(c) mesoderm

What is the function of gastrulation?

Explain how the flat embryonic disc takes on the cylindrical shape of a tadpole.

While Mark was cramming for his anatomy test, he read that some parts of the mesoderm become segmented. He suddenly realized that he could not remember what segmentation is. Define segmentation, and give two examples of segmented structures in the embryo.

Claire is a heavy smoker and has ignored a friend’s advice to stop smoking during her pregnancy. On the basis of what you know about the effect of smoking on physiology, describe how Claire’s smoking might affect her fetus.