41) The expression "breaking water" during birthing refers to the
A) amnion.
B) allantois.
C) chorion.
D) yolk sac.
42) Which characteristic is
not
true of a blastocyst?
A) It contains a fluid-filled cavity.
B) It develops 24-36 hours after conception.
C) It has an inner cell mass and an outer trophoblast.
D) It implants into the uterus.
43) The solid mass of cells that results from cleavage of the zygote is the
A) trophoblast.
B) blastocyst.
C) morula.
D) gastrula.
44) Which of the following does
not
distinguish mesoderm from either endoderm or ectoderm?
A) It is a mesenchyme tissue.
B) It is derived from the epiblast.
C) It is the last of the three germ layers to develop.
D) Its cells can migrate widely within the embryo.
45) The term
bilaminar disc
refers to the embryonic ________ and ________.
A) epidermis; dermis
B) ectoderm; mesoderm
C) epiblast; hypoblast
D) inner cell mass; trophoblast
46) Mesenchyme would refer to ________ but not ________.
A) mesoderm; ectoderm
B) ectoderm; mesoderm
C) endoderm; ectoderm
D) ectoderm; endoderm
47) Male and female fetuses can first be distinguished by their genitalia at
A) 1 week.
B) 3 weeks.
C) 3 months.
D) 7 months.
48) Thalidomide, once used to alleviate morning sickness in pregnant women, resulted in
A) severe limb abnormalities.
B) heart defects.
C) mental retardation.
D) multiple births.
49) Chemical, physical, or biological agents that can induce birth defects are called
A) mutagens.
B) teratogens.
C) free radicals.
D) carcinogens.
50) The most common cause of mental retardation in the United States is
A) anencephaly.
B) spina bifida.
C) fetal alcohol syndrome.
D) thalidomide.