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Development of the Heart in Human Embryos 1

Development of the heart in human embryos



A 25-year-old pregnant woman comes to the clinic for her first prenatal visit. She is in her second month of pregnancy and is concerned about her baby's development. She is a smoker and has been trying to quit since she found out about her pregnancy. She is particularly worried about the potential impact of smoking on her baby's developing heart. The physician explains that the heart is one of the first organs to form and function in the fetus. Which of the following best describes when the heart first begins to develop in human embryos?


A. At fertilization

B. During the second week of development

C. During the third week of development

D. During the fourth week of development

E. During the fifth week of development


C. During the third week of development


The heart begins to develop in the human embryo during the third week of embryonic development. This is the period of gastrulation, when the trilaminar germ disc forms, and the process of organogenesis begins. The heart originates from the mesoderm, specifically the splanchnic mesoderm, which folds to form the endocardial heart tubes. These heart tubes fuse to form a primitive heart tube, which starts to beat and pump blood by the end of the third week. Thus, harmful substances, such as the chemicals found in cigarette smoke, can potentially impact the development of the heart if exposure occurs during this critical period. This is why it is crucial for pregnant women to avoid smoking, especially early in pregnancy when organogenesis is taking place.


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