Final: Embryo Cole's Practice Questions

Question 1

• An ovum is fertilized. After 2 weeks a blastocyst implanted on the endometrium has an inner embryoblast and an outer trophoblast. Which of the following is the next step in forming a 3-layered embryonic disk?
• A Decidualization
• B Gastrulation
• C Lateralizaton
• D Neurulation
• E Placentation

Answer 1

• B Gastrulation : CORRECT. The 3 germ layers form in the process of gastrulation in the 3rd week of embryonic development

Question 2

• A study is performed involving women exposed to rubella virus during pregnancy. Some of them give birth to infants with abnormalities including deafness, blindness, intellectual disability, and seizure disorder. At what point in gestation is exposure to this virus most likely to be associated with appearance of these complications?
• A4weeks
• B12weeks
• C20weeks
• D28weeks
• E36weeks

Answer 2

• A 4 weeks - the critical period of embryonic development is weeks 3-8

Question 3

• The first week of human development is characterized by formation of the:
•
• A. inner cell mass
• B. hypoblast
• C. trophoblast
• D. blastocyst
• E. all of the above

Answer 3

E. all of the above:
At four days, the blastocyst cavity of blastocele forms within the morula. Trophoblast are outer cells of the blastocyst, while a knot of cells appears, protruding into the blastocele. This is the inner cell mass. Trophoblast becomes 2 layers: syncytiotrophoblast and cytotrophoblast. Inner cell mass becomes epiblast and hypoblast

Question 4

Theearlystagesofcleavagearecharacterizedby:
A. formation of a hollow ball of cells
B. formation of the zona pellucida
C. increase in the size of the cells in the zygote
D. increase in the number of cells in the zygote
E. none of the above

Answer 4

D. The earliest stages of cleavage are marked by a series of mitotic divisions that increase the number of cells in the zygote without an increase in size. As the cleavage continues the zygote becomes a morula or a solid ball of 12- 16 cels. A cavity forming within the morula transforms it into a blasocyst, at about day 4.

Question 5

he first two intraembryonic germ layers to differentiate are the:
A. ectoderm and hypoblast 
B. epiblast and hypoblast
C. ectoderm and endoderm 
D. ectoderm and mesoderm

Answer 5

B. The epiblast and hypoblast develop from the inner cell mass during the 2nd week. During the 3rd week, the epiblast produces cells between itself and the hypoblast, called the mesoderm. Epiblast also replaces the hypoblast with endoderm cells. Epiblast then changes its name to ectoderm, completing the process of gastrulation.

Question 6

Implantation of human embryos typically occurs:
A. about 1 day after fertilization
B. about one week(i.e.7days)after fertilization
C. about two weeks(i.e.14days)after fertilization
D. after gastrulation
E. at the same time as neural tube closure
F. NONE of the above

Answer 6

B

Question 7

A 19-year-old pregnant woman at 29 weeks gestation underwent routine prenatal sonography. A large fluid filled, intrauterine structure was found and she subsequently was referred to a tertiary care facility for further evaluation and management.
• MRI showed large cystic mass arising from the sacrococcygeal region of the fetus The patient was counseled and monitored until she presented in labor eight weeks later, with contractions every ten minutes, nausea, vomiting, and apparently decreased fetal activity. She was taken urgently to the operating room where a cesarean section was performed and the fetus was delivered without complication. At the time of delivery, the female neonate was noted to have a large, cystic sacrococcygeal mass (Fig. 2) measuring 19.1 cm by 9.7 cm by 13.2 cm. The mass had no solid components. The neonate was subsequently taken to surgery where the lesion was resected.

The MOST LIKELY cause for this congenital defect is:
A. abnormal migration and proliferation of lumbosacral neural crest.
B. abnormal persistence of primitive streak tissue after completion of gastrulation.
C. premature regression of the primitive streak during gastrulation.
D. abnormal closure of the posterior (caudal) neuropore.
E. abnormal left-right patterning due to ciliary dysfunction.

Answer 7

B

Question 8

Case w/ mother having baby with sacrococcygeal taratoma.

Histologic examination of the mass would reveal derivatives of which germ layer(s)?
• endoderm
• mesoderm
• ectoderm
• ALL of the above

Answer 8

D. All of the above