Chapter 28 Open Access

The only 100% effective method of birth control is __________.

total abstinence

Implantation of the blastocyst begins __________.

6-7 days after ovulation

The Apgar score range that indicates a healthy baby is __________.

8-10

Which statement about maternal hormones during pregnancy is accurate?

Estrogen levels increase throughout gestation.

By the third month of pregnancy, the corpus luteum is the most important organ making estrogen and progesterone.

False Between the second and third month, the placenta assumes the role of progesterone and estrogen production for the remainder of the pregnancy. The corpus luteum then degenerates and the ovaries remain inactive until after birth.

hCG remains the dominant hormone throughout pregnancy.

False Blood levels of hCG decline sharply to reach a low value by four months.

During the cleavage period, the embryo grows more than 10 times the size of the zygote.

False Cleavage produces a sphere of very small cells without intervening growth.

Gestation in humans lasts approximately 180 days.

False Gestation averages 280 days from the last menstrual period, or 9 months.

Fetal blood only mixes with the mother's blood in a small place in the placenta.

False The chorionic villi membrane and the endothelium of the fetal capillaries separate the two blood supplies.

The placenta is produced from the embryo's amnion.

False The placenta forms from the chorion and endometrium.

The yolk sac is an important nutritive agent for the embryo.

False The placenta is the nutritive agent for the embryo and fetus.

There are two umbilical veins and one artery.

False There are two umbilical arteries and one umbilical vein.

All EXCEPT which of the following statements about the foramen ovale are true?

It allows blood to pass directly from the right atrium into the left ventricle.

What is the function of the hormone hCG (human chorionic gonadotropin)?

It signals the corpus luteum to continue producing estrogen and progesterone to maintain the pregnancy.

Which of the following is NOT a function of trophoblast cells?

The inner layers of trophoblasts lose their plasmic membranes and invade the endometrium.

Testes develop within the body cavity but descend into the scrotum around the seventh month of development.

True

Once a sperm head enters an oocyte, blocks to polyspermy occur.

True Blocks to polyspermy, such as the oocyte releasing enzymes that destroy the sperm receptors, prevent any more sperm from entering the oocyte.

The first major event of organogenesis is neurulation.

True Derived from ectoderm, neurulation is the first major event of organogenesis.

Implantation begins approximately six to seven days after ovulation.

True Implantation begins about six to seven days after ovulation.

Gestational diabetes mellitus (which occurs in 10% of pregnancies) can often lead to development of type 2 diabetes later in life.

True Over 50% of the time, gestational diabetes mellitus can lead to later problems with diabetes mellitus type 2.

The ductus arteriosus allows fetal blood to bypass the lungs.

True The ductus arteriosus allows blood in the pulmonary trunk to enter the aorta, bypassing the lungs.

The early ventral body cavity forms from the lateral mesoderm.

True The lateral mesodermal layers cooperate to form the serosae of the coelom, or ventral body cavity.

When blood leaves the fetal heart, only part of it will pass to the placenta before returning to the heart again.

True The placenta receives blood from the umbilical arteries, which branch off from the internal iliac arteries.

All EXCEPT which of the following prevent polyspermy?

a decrease in zonal inhibiting proteins

The heart begins to beat in the developing offspring __________.

at about 3 1/2 weeks

Which of the following is NOT from the same germ line as the others?

brain

Which of the following structures is formed from ectodermal tissues?

brain

The function of the ductus arteriosus is to __________.

bypass the pulmonary circuit

The outermost embryonic membrane is the __________.

chorion

The disc-shaped placenta is formed from the __________.

chronic villi and the decidua basalis

After fertilization the zygote goes through a rapid period of cell divisions called

cleavage

Which sequence shows the correct order of the stages of labor?

dilation, expulsion, placental

An implantation that takes place in a site other than the uterus is called __________.

ectopic

Which structure represents the remnants of the atrial fetal shunt?

fossa ovalis

The process by which the three primary germ layers form is known as __________.

gastrulation

The process that transforms the embryo into a three-layered stage is called

gastrulation

Which of the following factors is NOT considered to be a teratogen?

iron

Which of the following is NOT a common metabolic/physiological change that occurs in pregnant women?

lower blood pressure

Prolactin causes __________.

milk production by the breast tissue

The first major event of organogenesis is __________.

neurulation

Sperm are known to bear __________ that respond to chemical stimuli that help them locate the ova.

olfactory receptors

The hormone that induces labor and controls labor via a positive feedback mechanism is __________.

oxytocin

Which hormone produced by the placenta causes the mother's pubic symphysis to loosen and widen?

relaxin

Meconium is __________.

sloughed epithelial cells, bile, and other substances

Implantation is usually completed after __________.

the blastocyst is entirely surrounded by endometrium

Which of the following is NOT a function of the placenta?

urine formation