During Week 4, the placenta develops to serve as which of the following?

• A. It serves as an early liver.
• B. It forms the brain.
• C. It becomes the heart.
• D. It forms the skeleton.

Answer: (A)

In Week 4 the placenta begins to provide essential metabolic support for the developing embryo. It acts as the main exchange interface, delivering nutrients from the mother, removing waste, and producing hormones that help maintain the pregnancy. Because that metabolic processing and nutrient handling are foundational to growth, this early placental role is sometimes described as taking on liver-like functions. The embryo’s own liver and other organs haven’t formed yet, so the placenta serves as the early support system for metabolism, which is why that option is the best fit. The brain, heart, and skeleton come from the embryo itself and develop separately as development progresses.