EMBRYOLOGY MCQs
By Joshua
(This MCQs spans the first 8 weeks of intrauterine development, curated to
help you trigger your sensory neurons before your exam or for revision
purpose)
Note that the questions are styled specially for USMLE STEP 1 exams, but can still
proof useful for other Entrance Exams.
Good Luck!
Block 1: Weeks 1–2
1. A 26-year-old woman undergoes in vitro fertilization and embryo
transfer. The embryo is placed into the uterine cavity on day 5 after
fertilization. What stage of development has the embryo reached by this
time?
A. Zygote
B. Morula
C. Blastocyst
D. Gastrula
E. Fetus
2. A woman at 6 weeks’ gestation has a positive pregnancy test but no
detectable embryonic structures on ultrasound. Which of the following
terms best describes this finding?
A. Anencephaly
, B. Blighted ovum (anembryonic pregnancy)
C. Ectopic pregnancy
D. Hydatidiform mole
E. Fetal demise
3. During normal fertilization and early development, which uterine tube
segment is most often the site of sperm-egg union?
A. Isthmus of uterine tube
B. Ampulla of uterine tube
C. Interstitial segment of uterine tube
D. Infundibulum of uterine tube
E. Uterine fundus
4. Two weeks after fertilization, the human conceptus has formed a two-
layered embryonic disc. Which of the following structures is derived
from the epiblast (upper layer) of the bilaminar disc?
A. Primary yolk sac
B. Umbilical cord
C. Amnion (amniotic membrane)
D. Hypoblast (primitive endoderm)
E. Chorionic villi
5. Which embryonic cell layer is the source of the cells that line the
primordial yolk sac by the end of week 2?
A. Epiblast
B. Hypoblast
C. Trophoblast
D. Syncytiotrophoblast
E. Neural crest
,6. During the cleavage stage of early embryogenesis (first few days post-
fertilization), which of the following is true?
A. Total volume of the embryo increases dramatically.
B. Cell number increases while the zona pellucida shrinks.
C. Embryonic cells migrate out of the zona pellucida.
D. The embryo remains roughly the same size despite cell divisions.
E. The inner cell mass forms before the outer cell mass.
7. On day 3 post-fertilization, the human embryo (zygote) would be best
characterized as which of the following?
A. Zygote with 2 pronuclei
B. Morula (solid ball of ~16 cells)
C. Embryonic disc
D. Blastocyst (with blastocoel cavity)
E. Neurula
8. Which trophoblast-derived tissue is responsible for secreting human
chorionic gonadotropin (hCG) in early pregnancy?
A. Cytotrophoblast
B. Syncytiotrophoblast
C. Epiblast
D. Hypoblast
E. Inner cell mass
9. Which structure arises from the inner cell mass (embryoblast) of a
blastocyst?
A. Placenta (via trophoblast)
B. Uterine endometrium
C. Embryo proper (future fetus)
, D. Maternal blood vessels
E. Extraembryonic mesoderm
10. During implantation of the blastocyst into the uterine wall, which of the
following occurs?
A. The hypoblast invades the endometrium.
B. Maternal blood first appears in lacunae formed in the syncytiotrophoblast.
C. The amnion fuses with the chorion.
D. Gastrulation is completed.
E. The primitive streak forms.
11. Which of the following statements about the zona pellucida is correct?
A. It is shed immediately after fertilization.
B. It prevents implantation while the blastocyst is in the uterine tube.
C. It releases enzymes that allow sperm penetration.
D. It contributes to forming the chorionic villi.
E. It becomes the primary yolk sac.
12. The term “pre-embryo” is used to describe the conceptus during which
time period?
A. Weeks 3–8 (trilaminar disc)
B. From fertilization up to formation of the bilaminar disc
C. Weeks 9–38 (fetal period)
D. At birth
E. None of the above
13. A chorionic villus biopsy is performed around day 12 of development.
Which cell layer is most directly sampled by this procedure?
A. Epiblast
B. Hypoblast
C. Cytotrophoblast (trophoblast)
By Joshua
(This MCQs spans the first 8 weeks of intrauterine development, curated to
help you trigger your sensory neurons before your exam or for revision
purpose)
Note that the questions are styled specially for USMLE STEP 1 exams, but can still
proof useful for other Entrance Exams.
Good Luck!
Block 1: Weeks 1–2
1. A 26-year-old woman undergoes in vitro fertilization and embryo
transfer. The embryo is placed into the uterine cavity on day 5 after
fertilization. What stage of development has the embryo reached by this
time?
A. Zygote
B. Morula
C. Blastocyst
D. Gastrula
E. Fetus
2. A woman at 6 weeks’ gestation has a positive pregnancy test but no
detectable embryonic structures on ultrasound. Which of the following
terms best describes this finding?
A. Anencephaly
, B. Blighted ovum (anembryonic pregnancy)
C. Ectopic pregnancy
D. Hydatidiform mole
E. Fetal demise
3. During normal fertilization and early development, which uterine tube
segment is most often the site of sperm-egg union?
A. Isthmus of uterine tube
B. Ampulla of uterine tube
C. Interstitial segment of uterine tube
D. Infundibulum of uterine tube
E. Uterine fundus
4. Two weeks after fertilization, the human conceptus has formed a two-
layered embryonic disc. Which of the following structures is derived
from the epiblast (upper layer) of the bilaminar disc?
A. Primary yolk sac
B. Umbilical cord
C. Amnion (amniotic membrane)
D. Hypoblast (primitive endoderm)
E. Chorionic villi
5. Which embryonic cell layer is the source of the cells that line the
primordial yolk sac by the end of week 2?
A. Epiblast
B. Hypoblast
C. Trophoblast
D. Syncytiotrophoblast
E. Neural crest
,6. During the cleavage stage of early embryogenesis (first few days post-
fertilization), which of the following is true?
A. Total volume of the embryo increases dramatically.
B. Cell number increases while the zona pellucida shrinks.
C. Embryonic cells migrate out of the zona pellucida.
D. The embryo remains roughly the same size despite cell divisions.
E. The inner cell mass forms before the outer cell mass.
7. On day 3 post-fertilization, the human embryo (zygote) would be best
characterized as which of the following?
A. Zygote with 2 pronuclei
B. Morula (solid ball of ~16 cells)
C. Embryonic disc
D. Blastocyst (with blastocoel cavity)
E. Neurula
8. Which trophoblast-derived tissue is responsible for secreting human
chorionic gonadotropin (hCG) in early pregnancy?
A. Cytotrophoblast
B. Syncytiotrophoblast
C. Epiblast
D. Hypoblast
E. Inner cell mass
9. Which structure arises from the inner cell mass (embryoblast) of a
blastocyst?
A. Placenta (via trophoblast)
B. Uterine endometrium
C. Embryo proper (future fetus)
, D. Maternal blood vessels
E. Extraembryonic mesoderm
10. During implantation of the blastocyst into the uterine wall, which of the
following occurs?
A. The hypoblast invades the endometrium.
B. Maternal blood first appears in lacunae formed in the syncytiotrophoblast.
C. The amnion fuses with the chorion.
D. Gastrulation is completed.
E. The primitive streak forms.
11. Which of the following statements about the zona pellucida is correct?
A. It is shed immediately after fertilization.
B. It prevents implantation while the blastocyst is in the uterine tube.
C. It releases enzymes that allow sperm penetration.
D. It contributes to forming the chorionic villi.
E. It becomes the primary yolk sac.
12. The term “pre-embryo” is used to describe the conceptus during which
time period?
A. Weeks 3–8 (trilaminar disc)
B. From fertilization up to formation of the bilaminar disc
C. Weeks 9–38 (fetal period)
D. At birth
E. None of the above
13. A chorionic villus biopsy is performed around day 12 of development.
Which cell layer is most directly sampled by this procedure?
A. Epiblast
B. Hypoblast
C. Cytotrophoblast (trophoblast)
