WBR0513
Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
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Exam Type | ExamType::USMLE Step 1 |
Main Category | MainCategory::Physiology |
Sub Category | SubCategory::Reproductive |
Prompt | [[Prompt::A couple, trying to conceive a child for 5 years, visits the in-vitro fertilization (IVF) center. The physician informs the family that during IVF, the embyro is directly implanted in the uterus. In a normal pregnancy, at which day post-fertilization does an embryo undergoes implantation in the uterus?]] |
Answer A | AnswerA::Day 2 |
Answer A Explanation | AnswerAExp::On day 2, the zygote is still within the fallopian tubes and has not descended to the level of the endometrium. |
Answer B | AnswerB::Day 4 |
Answer B Explanation | AnswerBExp::On day 4, the morula is still within the fallopian tubes and has not descended to the level of the endometrium. |
Answer C | AnswerC::Day 6 |
Answer C Explanation | AnswerCExp::On day 6, the blastocyst is in the endometrium and implantation begins. |
Answer D | AnswerD::Day 10 |
Answer D Explanation | AnswerDExp::By day 10, implantation already started and hCG is being secreted. |
Answer E | AnswerE::Day 12 |
Answer E Explanation | AnswerEExp::On day 12, implantation already started and hCG is being secreted. |
Right Answer | RightAnswer::C |
Explanation | [[Explanation::During a normal pregnancy, fertilization occurs at day 0. The fertilization process typically occurs in the ampullary-ischmic junction of the fallopian tubes. Soon following fertilization, the oocyte proceeds with the meiosis II that had been arrested after ovulation. The fertilized egg continues to descend along the fallopian tube as mitosis of the embryo progressively occurs, becoming a morula on day 3 and a blastocyst on day 5. On day 6, the blastocyst reaches the endometrium and implantation is initiated. The pregnancy becomes detectable by serum and urinary concentrations of hCG within 10-14 days post-fertilization. Educational Objective: Typically, blastocyst implantation occurs on day 6 post-fertilization. |
Approved | Approved::Yes |
Keyword | WBRKeyword::day 6, WBRKeyword::implantation, WBRKeyword::blastocyst, WBRKeyword::morula, WBRKeyword::secretion, WBRKeyword::hCG, WBRKeyword::zygote, WBRKeyword::fertilization, WBRKeyword::egg, WBRKeyword::oocyte, WBRKeyword::sperm, WBRKeyword::endometrium, WBRKeyword::uterus, WBRKeyword::IVF, WBRKeyword::pregnancy, WBRKeyword::meiosis, WBRKeyword::mitosis, WBRKeyword::reproduction |
Linked Question | Linked:: |
Order in Linked Questions | LinkedOrder:: |