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Test Your Knowledge and master Embryology
Embryology (Embryonic Period)
MCQ
1 / 15
A male newborn has a hemangioma on the left frontotemporal region of his face and scalp. The cells forming the hemangioma are derived from which of the following cell layers?
A hemangioma is a vascular tumor that can be present at birth in which the abnormal proliferation of blood vessels leads to a mass resembling a neoplasm. Hemangiomas are mesodermal in origin, in that they are formed by embryonic blood cells and the vascular endothelium formed by angioblasts
2 / 15
Which process establishes the three definitive germ layers?
Gastrulation establishes the three primary germ layers during week 3 of development. Neurulation is the process by which neuroectoderm forms the neural plate, which eventually folds to form the neural tube.
3 / 15
Which germ layers are present at the end of week 3 of development (day 21)?
During week 3 of development, the process of gastrulation, which establishes the three primary germ layers (ectoderm, intraembryonic mesoderm, and endoderm), occurs. The origin of all tissues and organs of the adult can be traced to one of these germ layers because these are whence they “germinate.”
4 / 15
A female newborn was found to have a large midline tumor in the lower sacral area, which was diagnosed as a sacrococcygeal tumor. Which of the following courses of treatment is recommended for this child?
The preponderance of sacrococcygeal tumors is found in female newborns. Because these tumors develop from pluripotent cells of primitive streak origin, malignancy is of great concern, and the tumor should be surgically removed by age 6 months. Occasionally, these tumors may recur after surgery, demonstrating malignant properties.
5 / 15
The developing embryo has a distinct human appearance by the end of
The embryo starts the embryonic period as a two-dimensional disk and ends as a threedimensional cylinder. This dramatic change in geometry is caused by formation of all the major organ systems. As the organ systems gradually develop during the embryonic period, the embryo appears more and more human-like; it has a distinct human appearance at the end of week 8.
6 / 15
The epiblast is capable of forming which of the following germ layers?
The epiblast is capable of forming all three germ layers (ectoderm, mesoderm, and endoderm) during gastrulation. Epiblast cells migrate to the primitive streak and invaginate into a space between the epiblast and hypoblast. Some of these epiblast cells displace the hypoblast to form the definitive endoderm. Migrating epiblast cells also form the intraembryonic mesoderm. The remaining epiblast cells form the ectoderm
7 / 15
Which structure is derived from the same embryonic primordium as the dorsal root ganglia?
Both the chromaffin cells of the adrenal medulla and the dorsal root ganglia are derived from neural crest cells
8 / 15
A woman has her pregnancy suddenly terminated due to intrauterine fetal death. At autopsy, the fetus shows severe pallor, generalized edema, and hepatosplenomegaly. Which of the following would you suspect?
Hydrops fetalis is the most severe form of α-thalassemia, and is a direct result of the lack or decreased synthesis of the α-globin chain of hemoglobin α2β2.
9 / 15
Intermediate mesoderm will give rise to the
Intermediate mesoderm is a subdivision of intraembryonic mesoderm that forms a longitudinal dorsal ridge called the urogenital ridge from which the kidneys and gonads develop.
10 / 15
The lateral mesoderm is divided into two distinct layers by the formation of the
The lateral mesoderm is a subdivision of intraembryonic mesoderm and initially is a solid plate of mesoderm. The intraembryonic coelom forms in the middle of the lateral mesoderm, thereby dividing it into the intraembryonic somatic mesoderm and intraembryonic visceral mesoderm.
11 / 15
The specialized group of mesenchymal cells that aggregate to form blood islands centrally and primitive blood vessels peripherally are called
The angioblasts are the mesenchymal cells that form blood vessels in embryonic development, as well as embryonic blood cells.
12 / 15
Which structure is derived from the same embryonic primordium as the kidney?
Both the kidneys and the gonads are derived from intermediate mesoderm. This longitudinal dorsal ridge of mesoderm forms the gonadal ridge, which is involved with the formation of the future kidneys and gonads.
13 / 15
Somites may differentiate into which of the following?
Approximately 35 pairs of somites form. They are derived from a specific subdivision of intraembryonic mesoderm called paraxial mesoderm. Somites differentiate into the components called sclerotome (cartilage and bone of the vertebral column), myotome (epimeric and hypomeric muscle), and dermatome (dermis and subcutaneous area of skin).
14 / 15
Very often the first indication a woman has that she is pregnant is a missed menstrual period. In which week of embryonic development will a woman experience her first missed menstrual period?
Given a regular 28-day menstrual cycle, a woman who starts menses on, say, February 1 will ovulate on February 14, and the secondary oocyte will be fertilized, if she becomes pregnant, within 24 hours. So, the zygote undergoes week 1 of development from February 15 to 21. Week 2 of development is from February 22 to 28. On the next day, March 1, the woman would enter her next menstrual cycle if she were not pregnant, but because she is pregnant, she does not menstruate. Therefore, this first missed menstrual period corresponds with the start of week 3 of embryonic development. The embryonic period (week 3–week 8) is a time of high susceptibility to teratogens.
15 / 15
The first indication of gastrulation in the embryo is
The formation of the primitive streak on the dorsal surface of the bilaminar embryonic disk is the first indication of gastrulation.
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