Problem
The human heart is the first functional organ to develop. It begins beating and pumping blood around day 21 or 22, a mere three weeks after fertilization. This emphasizes the critical nature of the heart in distributing blood through the vessels and the vital exchange of nutrients, oxygen, and wastes both to and from the developing baby (fetus). The fetal heart differs in structure and blood flow.
Explain the structural and the blood flow difference of the heart before and after birth and answer the following questions.
1. Why is the difference necessary?
2. What causes the changes in fetal heart after birth?