The zygote is the single diploid cell formed when a sperm fertilizes an oocyte.
Correct Answer
True
True. Each haploid gamete contributes 23 chromosomes, so fertilization restores the diploid number of 46 in the zygote, the first cell of the new individual.
Category: Fertilization
Question 2
The acrosome, a cap of digestive enzymes used to penetrate the coverings of the egg, is part of the oocyte.
Correct Answer
False
False. The acrosome is a cap on the head of the sperm. Its enzymes digest a path through the corona radiata and zona pellucida so the sperm can reach the oocyte membrane.
Category: Fertilization
Question 3
Down syndrome results from having only one copy of chromosome 21.
Correct Answer
False
False. Down syndrome is trisomy 21, meaning three copies of chromosome 21, most often caused by nondisjunction during meiosis. Having a single copy of a chromosome is called monosomy.
Category: Patterns of Inheritance
Question 4
Cleavage divisions increase the number of cells in the conceptus without increasing its overall size.
Correct Answer
True
True. During cleavage the zygote divides rapidly by mitosis into smaller and smaller blastomeres, so cell number rises while the total volume stays about the same.
Category: Embryonic Development
Question 5
The chorion is the outermost embryonic membrane and forms the fetal portion of the placenta.
Correct Answer
True
True. The chorion surrounds the embryo and the other membranes, and its villi make up the fetal side of the placenta where exchange with maternal blood occurs.
Category: Embryonic Development
Question 6
The endoderm gives rise to the skeleton, skeletal muscles, heart, and kidneys.
Correct Answer
False
False. These structures come from the mesoderm. The endoderm forms the epithelial lining of the digestive tract and organs such as the liver, pancreas, and lungs.
Category: Embryonic Development
Question 7
Folate deficiency early in pregnancy increases the risk of neural tube defects such as spina bifida.
Correct Answer
True
True. The neural tube closes very early in development, often before a pregnancy is recognized, and adequate folate is needed for normal closure. This is why folic acid is recommended for anyone who may become pregnant.
Category: Embryonic Development
Question 8
In the placenta, maternal blood and fetal blood mix directly with each other.
Correct Answer
False
False. Maternal and fetal blood stay separated by the tissue of the chorionic villi. Gases, nutrients, and wastes cross this barrier by diffusion and transport rather than by mixing of blood.
Category: Embryonic Development
Question 9
In the fetus, the foramen ovale allows blood to pass directly from the right atrium to the left atrium.
Correct Answer
True
True. Because the fetal lungs are not used for gas exchange, much of the blood entering the right atrium crosses through the foramen ovale into the left atrium and bypasses the pulmonary circuit.
Category: Fetal Development
Question 10
X-linked recessive disorders such as hemophilia are more common in males than in females.
Correct Answer
True
True. Males have only one X chromosome, so a single recessive allele on it is expressed. Females usually need two copies to be affected, which is much less likely.
Category: Patterns of Inheritance
Question 11
In a female fetus, the Wolffian ducts develop into the uterine tubes and uterus.
Correct Answer
False
False. In a female fetus the Wolffian ducts degenerate, and the Müllerian ducts form the uterine tubes and uterus. In a male fetus the Wolffian ducts develop into structures such as the vas deferens.
Category: Fetal Development
Question 12
Progesterone stimulates uterine contractions throughout pregnancy.
Correct Answer
False
False. Progesterone inhibits contractions of the myometrium and helps maintain the pregnancy. Late in pregnancy the balance shifts toward estrogen, which makes the uterus more responsive to oxytocin.
Category: Pregnancy and Labor
Question 13
Huntington disease is inherited in an autosomal dominant pattern.
Correct Answer
True
True. A single copy of the Huntington allele causes the disease. Because symptoms usually begin in middle age, after many people have had children, the allele can be passed on despite being lethal.
Category: Patterns of Inheritance
Question 14
Braxton Hicks contractions are strong, regular contractions that progressively dilate the cervix.
Correct Answer
False
False. Braxton Hicks contractions are weak and irregular and do not produce progressive dilation, which is why they are called false labor. They often ease with rest or hydration.
Category: Pregnancy and Labor
Question 15
At the end of the first stage of labor, the cervix is fully dilated to about 4 cm.
Correct Answer
False
False. Full cervical dilation is 10 cm, which marks the end of the first stage of labor and allows the fetus to pass into the vagina.
Category: Pregnancy and Labor
Question 16
Delivery of the placenta and fetal membranes makes up the third stage of labor.
Correct Answer
True
True. After the newborn is delivered, continued uterine contractions detach and expel the placenta and membranes, which is called the afterbirth. They are inspected to make sure no fragments remain that could cause hemorrhage.
Category: Pregnancy and Labor
Question 17
The rise in blood oxygen after birth causes the ductus arteriosus to constrict and close.
Correct Answer
True
True. Higher oxygen levels once the lungs begin breathing trigger constriction of the ductus arteriosus, which later becomes the ligamentum arteriosum. All blood leaving the right ventricle then flows to the lungs.
Category: Newborn Adjustments
Question 18
After birth, the ductus venosus becomes the ligamentum arteriosum.
Correct Answer
False
False. The ductus venosus degenerates into the ligamentum venosum on the liver. The ligamentum arteriosum is the remnant of the ductus arteriosus, which connected the pulmonary trunk to the aorta.
Category: Newborn Adjustments
Question 19
Suckling triggers oxytocin release, which contracts myoepithelial cells around the alveoli to eject milk.
Correct Answer
True
True. Touch receptors in the nipple and areola send signals that cause the posterior pituitary to release oxytocin. Oxytocin squeezes the myoepithelial cells, pushing milk into the ducts and out of the nipple in the let-down reflex.
Category: Lactation
Question 20
High levels of estrogen and progesterone during pregnancy stimulate full milk production before birth.
Correct Answer
False
False. Estrogen, progesterone, and other placental hormones inhibit full prolactin-driven milk synthesis during pregnancy, although small amounts of colostrum are made. Copious milk production begins after the placenta is delivered and this inhibition is removed.
Category: Lactation