During the third week of development, the blastocyst undergoes a variety of differentiation processes responsible for the formation of the gastrula and, eventually, the embryo. This differentiation creates cell lineages that eventually become a variety of body systems. What cell lineage, present at this date, is responsible for the formation of the liver?
ANeuroectoderm
BSyncytiotrophoblasts
CEctoderm
DEndoderm
EMesoderm
A 21-year-old G3P2 woman presents to her obstetrician at 6 weeks gestation for routine prenatal care. Her past medical history includes obesity and gestational diabetes. She has had two spontaneous vaginal deliveries at term. One infant was macrosomic with hypoglycemia, but otherwise, she has had no complications. Her physician informs her that she must start taking a multivitamin with folic acid daily. The defect that folic acid supplementation protects against arises in tissue that is derived from which germ cell layer?
AMesoderm
BNotochord
CEndoderm
DMesenchyme
EEctoderm
A 32-year-old G1P0 woman undergoes her 2nd-trimester ultrasound in a community hospital. During her prenatal care, she was found to have mild anemia, low levels of folate, and serum alpha-fetoprotein levels greater than 2 multiples of the median (MoM) on 2 separate occasions. Her 1st-trimester ultrasound was significant for the absence of the intracranial lucency, no visualization of the cisterna magna, and posterior shift of the brain stem. These 2nd-trimester ultrasound reports reveal the widening of the lumbosacral spine ossification centers and the presence of a sac in proximity to the lumbosacral defect. Which of the following statements best describes the congenital defect in the fetus?
AAbnormal development of the caudal eminence
BPersistence of the anterior accessory neurenteric canal (ANC)
CFailure of the caudal neuropore to close
DFailure of mesenchymal cells to form a neural rod
EFailure of the rostral neuropore to close
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