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

Most systems are operational in the fetus by four to six months. Which system is the exception to this generalization, affecting premature infants?

(a) the circulatory system

(b) the respiratory system

(c) the urinary system

(d) the digestive system

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

In the fetus, the ductus arteriosus carries blood from

(a) the pulmonary artery to the pulmonary vein

(b) the liver to the inferior vena cava

(c) the right ventricle to the left ventricle

(d) the pulmonary trunk to the aorta

Which of the following changes occur in the baby’s cardiovascular system after birth?

(a) umbilical arteries and vein become fibrosed

(b) pulmonary circulation begins to function, and pressure in the left side of the heart increases

(c) the ductus venosus becomes obliterated, as does the ductus arteriosus

(d) all of these

The umbilical vein carries

(a) waste products to the placenta

(b) oxygen and food to the fetus

(c) oxygen and food to the placenta

(d) oxygen and waste products to the fetus

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

(a) ectoderm

(b) endoderm

(c) mesoderm

The most important hormone in initiating and maintaining lactation after birth is

(a) estrogen

(b) FSH

(c) prolactin

(d) oxytocin

The initial stage of labor, during which the neck of the uterus is stretched, is the

(a) dilation stage

(b) expulsion stage

(c) placental stage

Cite two problems with a breech presentation.

What factors are believed to bring about uterine contractions at the termination of pregnancy?

During Mrs. Li’s labor, the obstetrician decided that it was necessary to perform an episiotomy. What is an episiotomy, and why is it done?

What is the function of hCG and why is it not important after the first trimester of pregnancy?

Cleavage is an embryonic event that mainly involves mitotic divisions. How does cleavage differ from mitosis occurring during life after birth, and what are its important functions?

The life span of the ovarian corpus luteum is extended for nearly three months after implantation, but otherwise it deteriorates.

(a) Explain why this is so.

(b) Explain why it is important that the corpus luteum remain functional following implantation.

Why is it that only one sperm out of the hundreds (or thousands) available enters the oocyte?

What is the function of gastrulation?

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

Jenna, a freshman in your dormitory, tells you she just discovered that she is three months pregnant. She recently bragged that since she came to college she has been drinking alcohol heavily and experimenting with every kind of recreational drug she could find. From the following, select the advice you would give her, and explain why it is the best choice.

(a) She must stop taking drugs, but they could not have affected her fetus during these first few months of her pregnancy.

(b) Harmful substances usually cannot pass from mother to embryo, so she can keep using drugs.

(c) There could be defects in the fetus, so she should stop using drugs and visit a doctor as soon as possible.

(d) If she has not taken any drugs in the last week, she is okay.

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.

Fertilization involves much more than a mere restoration of the diploid chromosome number.

(a) What does the process of fertilization entail on the part of both the egg and sperm?

(b) What are the effects of fertilization?

The placenta is a marvelous, but temporary, organ. Starting with a description of its formation, show how it is an intimate part of both fetal and maternal anatomy and physiology during the gestation period.

A woman in substantial pain called her doctor and explained (between sobs) that she was about to have her baby “right here.” The doctor calmed her and asked how she had come to that conclusion. She said that her water had broken and that her husband could see the baby’s head.

(a) Was she right? If so, what stage of labor was she in?

(b) Do you think that she had time to make it to the hospital 60 miles away? Why or why not?

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.