WBR1012

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Hematology
Prompt	[[Prompt::The concentrations of different types of hematopoietic stem cells are measured in various organs extracted from aborted fetuses. Shown below is an image that depicts hematopoiesis in various organs throughout fetal life and adulthood. Which of the following most likely represents hematopoiesis in the liver? ]]
Answer A	AnswerA::A
Answer A Explanation	[[AnswerAExp::Option A depicts erythropiesis in the bone marrow, which typically starts at 18 weeks gestation and continues throughout adulthood.]]
Answer B	AnswerB::B
Answer B Explanation	[[AnswerBExp::Option B depicts erythropoiesis in the spleen, which typically occurs between 10 weeks and 28 weeks of gestation.]]
Answer C	AnswerC::C
Answer C Explanation	[[AnswerCExp::Option C depicts erythropoiesis in the liver, which typically starts in the fetus at 6 weeks of gestation and continues until birth.]]
Answer D	AnswerD::D
Answer D Explanation	[[AnswerDExp::Option D depicts erythropoiesis in the yolk sac, which typically starts in the fetus at 3 weeks of gestation and continues until 8 weeks of gestation.]]
Answer E	AnswerE::E
Answer E Explanation	AnswerEExp::Option E is not characteristic of hematopoiesis in any organ.
Right Answer	RightAnswer::C
Explanation	[[Explanation::The site of erythropoiesis varies according to the age of the fetus. Fetal erythropoiesis occur in the following organs: Yolk sac: 3 weeks - 8 weeks Liver: 6 weeks - birth Spleen: 10 weeks - 28 weeks Bone marrow: 18 weeks - adulthood Shown below is an image that depicts erythropoiesis in fetuses and adults. Educational Objective: Erythropoiesis in the liver typically starts in the fetus at 6 weeks of gestation and continues until birth. References: First Aid 2014 page 270.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Erythropoiesis, WBRKeyword::Fetal erythropoiesis, WBRKeyword::Blood, WBRKeyword::Development, WBRKeyword::Fetus, WBRKeyword::Liver
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::