Fetal Period

MULTIPLE CHOICE

Directions: Each group of questions below consists of a numbered list of descriptive words or phrases accompanied by a diagram with certain parts indicated by letters or by a list of lettered headings. For each numbered word or phrase, select the lettered part or heading that matches it correctly and then insert the letter in the space to the right of the appropriate number. Sometimes more than one numbered word or phrase may be correctly matched to the same lettered part or heading.

        1.  

________ Amniotic sac

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

The amniotic sac contains amniotic fluid, which permits free movement of the fetus and symmetric external growth. The fluid also cushions the fetus against jolts the mother may receive and helps to control the fetus’s body temperature.

        2.  

________ Contains umbilical vessels

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   C

The umbilical cord contains umbilical vessels, normally two arteries and one vein. The vein carries nutrients and oxygenated blood to the fetus, and the arteries carry poorly oxygenated blood and waste products to the placenta, where the carbon dioxide and waste substances are transferred to the maternal blood for disposal.

        3.  

________ Chorionic sac

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   E

The chorionic sac at this stage normally is embedded in the endometrium and contains the embryo in its amniotic sac. Chorionic villi cover most of the outer wall of the sac at this stage. Some villi have degenerated because they were compressed and received insufficient blood supply for survival.

        4.  

________ Vestigial structure

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

The small remnant of the umbilical vesicle (yolk sac) indicated is a vestigial structure, serving no function at this stage. Part of the early umbilical vesicle is incorporated into the embryo during the fourth week as the primordial gut. Within a few weeks, the remnant of the umbilical vesicle indicated degenerates and disappears.

        5.  

________ Chorionic villi

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

Chorionic villi project from the wall of the chorionic sac. These important parts of the placenta normally are embedded in the endometrium and bathed in maternal blood. It is through the villi that the exchange of nutrients between mother and fetus takes place.

        6.  

________ Ensheathed by amnion

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   C

The umbilical cord has an external investment of amnion. As the amniotic sac enlarges, the amnion gradually forms the outer covering of the cord.

        7.   ________ Skin is wrinkled and pink to red

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   D

During the 21- to 25-week period, the skin usually is wrinkled and pink to red because blood in the capillaries is visible through the thin, transparent skin. During the subsequent 4 weeks, considerable subcutaneous fat forms, smoothing out many of the wrinkles.

        8.   ________ Quickening usually occurs

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   C

During the 17- to 20-week period, movements of the fetus—quickening—usually are felt by the mother for the first time. Although the fetus begins to move several weeks earlier, the movements are usually too slight to be felt by the mother.

        9.   ________ Skeleton first shows clearly on radiographs and sonograms

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   B

Toward the end of the 13- to 16-week period, the skeleton clearly shows on radiographs (x-ray films). Care is taken to prevent the fetus from receiving too much radiation because of the possible adverse effects on its germ cells and developing brain. Sonography is widely used for examining the fetus.

      10.   ________ Sex is first distinguishable externally

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   A

Sex is first distinguishable during the 8- to 12-week period. At 8 weeks, the external genitalia of males and females appear similar. By the tenth week, it may be possible to differentiate between males and females, but the mature form of the genitalia is not reached until the 12th week.

      11.   ________ Eyebrows, head hair, and lanugo are first visible

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   C

The 17- to 20-week period is important for several reasons. Fetal movements are first felt by the mother; vernix caseosa forms and affords protection for the fetal skin; lanugo, head hair, and the eyebrows become visible; and brown fat begins to form. This specialized fat is an important site of heat production.

      12.   ________ Head constitutes about half of the fetus

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   A

At the beginning of the fetal period, the head constitutes about half the length of the fetus. Thereafter, there is a relative slowdown in the growth of the head compared with the rest of the body. The large head in early fetuses results from the rapid development of the brain.

      13.   ________ Fetus has a good chance of surviving if born prematurely

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   E

By the 26- to 29-week period, the fetus has a reasonably good chance of surviving if it is born prematurely and is given intensive care; however, the mortality rate usually is high because of respiratory difficulties. The fetus is able to survive primarily because its respiratory and nervous systems have matured to the stage where rhythmic breathing can occur. Capillary proliferation in the lungs becomes active during this period. Before the 26- to 28-week period, the pulmonary vascular bed is unable to accommodate the entire cardiac output and so gas exchange in the lungs may not be adequate to support life.

      14.   ________ Brown fat begins to form

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   C

Brown fat begins to form by the 20-week period. Heat is produced in this specialized adipose tissue, particularly during the newborn period, by oxidizing fatty acids. Brown fat is found chiefly at the root of the neck, posterior to the sternum, and in the perirenal regions.

      15.   ________ Stage of initial activity of the fetus

A.
12 weeks
B.
16 weeks
C.
20 weeks
D.
25 weeks
E.
29 weeks

ANS:   A

The stage of initial activity is during the 8- to 12-week period. By the end of 12 weeks, stroking the lips of a fetus causes it to begin sucking, and if the eyelids are stroked, there is a reflex response. These early movements of the fetus are too slight to be felt by the mother. She usually cannot detect fetal movements until the 17- to 20-week period; these movements—quickening—constitute a positive sign of a living fetus.