Chapter 3: Fetal Development

The primary purpose of amniotic fluid is to: A. speed maturation of fetal lungs B. prevent cold stress after birth C. protect the fetus during development D. produce hormones to maintain pregnancy.

C. protect the fetus during development Rationale: Amniotic fluid has five major purposes that are all protective: maintaining temperature, preventing membranes from adhering to skin, allowing room for symmetrical growth, providing a cushion, and allowing buoyancy. Amniotic fluid does not speed lung development, although drugs given to the mother can speed lung development. Amniotic fluid helps maintain the stability of the fetal temperature, but will be gone after birth. The placenta is the pregnancy organ that produces hormones.

The maternal hormone _________________ reduces uterine contractions to prevent spontaneous abortions.

Progesterone Rationale: One of the functions of progesterone is to reduce uterine contractions and is sometimes supplemented by physicians to prevent spontaneous abortions. (39)

What functions does the amniotic fluid have? A. Allows buoyancy and fetal movement. B. Nourishes the fetus C. Maintains an even temperature D. Allows for symmetrical growth E. Provides for fetal circulation

A. Allows buoyancy and fetal movement. C. Maintains an even temperature D. Allows for symmetrical growth Rationale: The following are functions of amniotic fluid: maintains even temperature; prevents amniotic sac from adhering to the fetal skin; allows symmetrical growth, buoyancy, and fetal movement; and acts a cushion to protect the fetus and umbilical cord from injury. The placenta—not the amniotic fluid—nourishes the fetus and plays a significant role in fetal circulation. (35)

Which hormone is produced by the placenta? A. Estrogen B. LH (lutenizing hormone) C. Testosterone D. Aldosterone

A. Estrogen Rationale: Luteinizing hormone is produced by the anterior pituitary. Testosterone is produced by the testes. Aldosterone is secreted by the adrenal cortex. (39)

Most fetal blood bypasses circulation to the lungs by way of the: A. ducts venousus B. foramen ovale C. umbilical vein D. umbilical artery

B. foramen ovale Rationale: Only a small amount of blood goes into the fetal lungs to nourish them while they develop. Most blood goes from the right atrium to the left atrium through the foramen ovale, thus bypassing the lungs. The ductus venosus allows most blood from the placenta to bypass the liver. The umbilical vein and umbilical artery are structures within the umbilical cord that carry blood from the body to the placenta and return it to the body after oxygenation and removal of wastes.

After six weeks gestation, fetal red blood cells are manufactured in the: A. yolk sac B. liver C. bone marrow D. placenta

B. liver Rationale: The embryonic yolk sac functions only during embryonic life and initiates the production of red blood cells. This function continues for about 6 weeks until the embryonic liver takes over, followed by the bone marrow. The placenta uses fetal blood cells to deliver oxygen and nutrition to the fetus and to remove fetal waste products.

After fertilization, the zygote grows by: A. meiosis B. mitosis C. oogenesis D. gametogenesis

B. mitosis Rationale: After fertilization, the zygote must reproduce cells for growth by ordinary cell division (mitosis) to continue development. Meiosis is reduction cell division to produce gametes, or reproductive cells. The process of mitosis in the sperm is called spermatogenesis, and in the ovum it is called oogenesis. Finally, formation of gametes by this type of cell division is called gametogenesis.

An expectant mother is at her first prenatal visit. She informs the nurse that she smokes cigarettes but has cut back to approximately 10 cigarettes per week and asks if she may continue to smoke this many per week. What would be the best response? A. "That is something you should ask the physician." B. "You should decrease the amount of cigarettes you smoke." C. "Occasional smoking is not proven to be harmful during pregnancy." D. "Factors such as smoking and alcohol use may adversely affect your baby's development."

D. "Factors such as smoking and alcohol use may adversely affect your baby's development." Rationale: Harmful substances such as nicotine are transferred to the fetus and may cause fetal abnormalities or altered fetal growth and development. (31)

Which statements are true about the placenta? (Select all that apply.) A. It produces estrogen which stimulates the development of breasts for lactation. B. It serves as an organ for fetal respiration, nutrition, and excretion. C. It is much larger than the fetus during the entire pregnancy. D. It functions as an endocrine gland during the pregnancy. E. It is always present in the uterus; it just grows in size during pregnancy.

A. It produces estrogen which stimulates the development of breasts for lactation. B. It serves as an organ for fetal respiration, nutrition, and excretion. D. It functions as an endocrine gland during the pregnancy. Rationale: There are three statements that are true about the placenta. The placenta is larger than the fetus only during the early part of the pregnancy. A placenta grows during a pregnancy and is not present at other times. (38-39)

Why are twins often born early? A. The uterus becomes over distended. B. The placenta becomes distended C. The woman's body cannot tolerate the weight. D. The fetuses become too large to deliver vaginally.

A. The uterus becomes over distended. Rationale: Many twin or higher multiples are born prematurely because the uterus becomes overly distended and irritable. (42)

Hereditary or genetic traits are passed from one generation to the next within the: A. chromosomes B. zygote C. chorionic villi D. somatic cells

A. chromosomes Rationale: Genes are the smallest units of heredity and are located on chromosomes. The zygote is the developing baby for the first 2 weeks after conception. The placenta forms when the chorionic villi of the embryo extend into the bloodfilled spaces of the mother's decidua basalis. Somatic cells are nonreproductive, or body cells.

The sex of identical (monozygotic) twins: A. is always the same B. may or may not be the same C. is always different D. is not predictable

A. is always the same Rationale: Identical twins are of the same sex because they have the same genetic composition, including sex chromosomes. Although a couple may have more than one set of dizygotic, or fraternal, twins and each set may have one child of each sex, it occurs by chance and is not predictable.

The primary function of Wharton's jelly is to: A. keep the three placental blood vessels separated to improve flow B. prevent penetration of a fertilized ovum C. move sperm through the cervix and the uterus and into the fallopian tubes D. carry fetal waste products back into the placenta

A. keep the three placental blood vessels separated to improve flow Rationale: Umbilical vessels are coiled within the umbilical cord. Wharton's jelly covers and cushions the cord vessels and keeps the three vessels separated. As soon as fertilization occurs, a chemical change in the membrane around the fertilized ovum—not Wharton's jelly—prevents penetration by another sperm. Sperm pass through the cervix and the uterus and into the fallopian tubes by means of the agellar (whiplike) activity of their tails. Fetal deoxygenated blood and waste products leave the fetus through the two umbilical arteries and enter the placenta through the branch of a main stem villus.

A woman who wants to become pregnant should avoid all medications unless they are prescribed by a physician who knows she is pregnant, because: A. the placenta allows most medications to cross into the fetus. B. medications often have adverse effects when taken during pregnancy. C. fetal growth is likely to be slowed by many medications. D. the pregnancy is likely to be prolonged by some medications.

A. the placenta allows most medications to cross into the fetus. Rationale: The thin placental membrane provides some protection, but it is not a barrier to most substances ingested by the mother. Many harmful substances such as drugs, nicotine, and viral infectious agents are transferred to the fetus and may cause fetal drug addiction, congenital anomalies, and fetal infection. (39)

Which is the outer fetal membrane? A. Trophoblast B. Chorion C. Amnion D. Yolk sac

B. Chorion Rationale: The chorion develops from the trophoblast (the outer layer of embryonic cells) and envelops the amnion, embryo, and yolk sac. The amnion is the inner membrane that extends across the placenta and umbilical cord.

Fetal waste products are disposed of by the: A. fetal liver B. placenta C. yolk sac D. endoderm

B. placenta Rationale: Among its functions, the placenta eliminates fetal waste products, substituting for the fetal liver, kidneys, and other organ systems. The yolk sac produces red blood cells in early development. Endoderm refers to one of the embryonic cell layers.

Inadequate progesterone is likely to result in: A. release of multiple ova B. spontaneous abortion C. persistence of the corpus lute D. mixture of maternal and fetal blood

B. spontaneous abortion Rationale: One of progesterone's effects is to reduce uterine contractions that would otherwise tend to occur with stretching by the growing baby. Spontaneous abortion is likely if there is insuficient progesterone to quiet the uterus. Release of multiple ova would result from development and release of two or more of these gametes and is not controlled by progesterone. Human chorionic gonadotropin (hCG) signals the corpus luteum to persist and continue production of estrogen and progesterone. Maternal and fetal blood do not normally mix before birth.

The fetal circulatory structure that carries blood with the lowest oxygen saturation is the: A. umbilical vein B. umbilical artery C. ductus venous D. ductus ateriosus

B. umbilical artery Rationale: Because the umbilical arteries carry blood from the fetus to the placenta, most of the oxygen and nutrients have been consumed and carries blood having a high concentration of fetal wastes. The umbilical vein carries blood with the highest concentration because it is returning from the placenta. The ductus venosus and ductus arteriosus are fetal circulatory bypasses to shunt most oxygenated blood away from the liver (ductus venosus) and lungs (ductus arteriosus).

What is the most accurate response from a nurse when a pregnant woman having an ultrasound at 8 weeks of gestation asks if she may learn her expectant child's sex? A. "Yes, we will be able to tell the sex of your child." B. "No, the sex organs have not yet started to develop." C. "We will have tow wait until the birth of your child to know for sure." D. "The tenth week is when the external genitalia are visible on ultrasound."

D. "The tenth week is when the external genitalia are visible on ultrasound." Rationale: By 8 weeks of gestation, the ovaries or testes are present and the beginnings of all systems have developed. By the tenth week, the external genitalia are visible to ultrasound examination. (37)

What is the usual site of implantation for the female reproductive system? A. Edge of the inner cervical os B. Outer third of the fallopian (uterine) tube C. Lower section of the posterior uterine wall D. Upper section of the posterior uterine wall.

D. Upper section of the posterior uterine wall. Rationale: The zygote usually implants in the upper section of the posterior uterine wall. (35)

The purpose of the foramen oval is to: A. increase fetal blood flow to the lungs. B. limit blood flow to the liver C. raise the oxygen content of fetal blood D. reduce blood flow to the lungs.

D. reduce blood flow to the lungs. Rationale: The foramen ovale diverts most blood from the right atrium directly to the left atrium, rather than circulating it to the lungs. Therefore, blood flow to the lungs is reduced. (39)

The child's sex is determined by the: A. dominance of either the X or the Y chromosome B. number of X chromosomes in the ovum. C. ovum, which contributes either an X or a Y chromosome D. sperm, which contains either an X or a Y chromosome

D. sperm, which contains either an X or a Y chromosome Rationale: The ovum always contributes an X chromosome (gamete), but the sperm can carry an X or a Y chromosome (gamete). (33-34)

Fraternal (dizygotic) twins result when: A. they develop from a single fertilized ovum. B. two sperm fertilize one ovum C. the embryonic disc does not divide completely. D. two sperm fertilize two ova

D. two sperm fertilize two ova Rationale: Dizygotic (DZ) twins, also called fraternal twins, develop from two separate ova fertilized by two separate sperm. Monozygotic, or identical twins, develop from a single fertilized ovum. Two sperm cannot fertilize the same ovum. Siamese, or conjoined, twins form when the embryonic disc does not divide completely.

When a couple has unprotected sexual intercourse 4 days before the woman ovulates, the risk of the woman becoming pregnant is: A. limited, because the ova only lives for 24 hours. B. very high, because both the ova and the sperm are capable of fertilizing at that time. C. unknown D. very low, because that is not the woman's fertile period"

D. very low, because that is not the woman's fertile period" Rationale: The time during which fertilization can occur is brief because of the short life span of mature gametes. The ovum is estimated to survive for up to 24 hours after ovulation. The sperm remains capable of fertilizing the ovum for up to 5 days after being ejaculated into the area of the cervix. Therefore, the risk of pregnancy when unprotected intercourse occurs 4 days prior to ovulation is very low, because this is not the woman's fertile period. (33)

The fetal nervous system is formed by the germ layer known as the _____________.

ectoderm Rationale: The ectoderm forms the fetal nervous system. The mesoderm forms muscles, bone, cartilage, teeth dentin, ligaments, tendons, kidneys, heart, and other structures. The endoderm forms the epithelium of the digestive tract and respiratory tract. (35, Box 3-1)